Debian

Calculate and display effective CPU frequency (MHz) per process.

Build your own S3-compatible storage with Garage, a lightweight, distributed storage solution delivered as a single binary that’s ideal for homelab deployments.

Counterfeit SD cards report false capacity and corrupt data silently, so use f3 to detect these issues in minutes.

Fix the Too many applications are requesting to monitor file changes.

Use apt changelog to inspect package changelog in Debian-based systems before upgrading.

Display storage devices.

Extract the pre-installed Windows product key from the Microsoft Data Management table.

Match and control specific processes.

Use Memory BandWidth benchmark to benchmark memory bandwidth and verify dual-channel memory configuration is active.

Check if directory is a mountpoint with specified filesystem type before performing operations like backups.

Dump web-page inside terminal.

Remove RAID metadata from component device to ensure the system does not try to re-add it to the array or prepare it for a different purpose.

When you need to inspect the contents of an ISO image without mounting it, the isoinfo utility provides a convenient way to list files and extract metadata.

Read, back up, and burn DVD media (write-once DVD-R and rewritable DVD+RW, data, session at once) using external recorder.

Reexecute systemd manager to reload system configuration.

Output null separated data in awk using printf.

Generate locally administered unicast MAC addresses.

Check if service configuration is outdated and needs a systemd daemon configuration reload.

Whipper is a CD ripper that prioritizes accuracy over speed, using AccurateRip verification and detailed logging to ensure bit-perfect rips.

Alter /tmp (tmpfs) size.

Drop swap automatically using shell script.

Use built-in script command to record everything displayed in your terminal session to a file.

Learn how to set up automatic tmux session management when connecting via SSH.

Rename Software RAID array.

Create software RAID 1/5/6/10.

Access collaborative cheatsheets for console commands in command-line.

Extract INI sections and keys from the command-line.

Securely execute single command over ssh

Check known host fingerprint using bash function.

Regenerate OpenSSH host keys and update host key database on client.

Display sensor information.

Increase rebuild transfer speed.

Change Active State Power Management policy which determines how aggressively PCIe devices save power.

Lower your homelab Proxmox power consumption by changing the CPU scaling governor from performance to powersave mode.

Display installed hardware memory banks.

Convert apt sources.list to the modern .sources format (DEB822).

Display CPU count and model name.

Determine amount of total physical installed memory.

Create lightweight container with Podman within a systemd-nspawn machine.

Determine HP Lights-Out IP address.

Create lightweight container using systemd.

Use self-signed certificate to access git provider from Komodo.

Create on-demand local port forwarding with systemd and ssh.

Create SSH tunnel using systemd.

Upgrade Debian Bookworm to Trixie.

Expose any service on a port or socket with systemd.

Configure custom DNS servers for the NetBird interface wt0 using systemd.

Check environment variables for systemd service.

Force apt to use a specific IP protocol.

Use chrony with custom configuration and override brace systemd directives.

Compute and check SHA message digest.

Check if Debian system is running the newest installed kernel.

Disable scripting in Redis.

Manage your processes using PM2 Runtime Process manager.

To generate recovery data for your files using PAR2, you are essentially creating a Reed-Solomon matrix which is a mathematical construct that encodes your original data with redundancy, allowing for the reconstruction of missing or corrupted information.

Logitech MX Keys S keyboard takes a long time to reconnect after waking system up. The solution is to blacklist the hid-vivaldi driver. This prevents it from loading during startup, forcing the system to use a more compatible generic HID driver, which will resolve the connection problems.

Install Komodo build and deployment system.

Determine Secure Boot state.

Initialize the machine ID.

Install and configure chrony as client only for time synchronization.

Elevate privileges with doas.

Guarantee that the task is executed to catch up on a missed systemd schedule.

Change time zone using timedatectl.

Automate APT logging with JSON using hooks.

How to get structured JSON from command-line utilities using jc.

Configure sudo credential caching.

Determine if specific package is installed.

Calculate upgrade size.

List upgradeable packages with apt and apt-get.

Suppress the apt-get simulation note.

Suppress the apt script warning message.

Wake operating system at specific time.

Automatically decrypt LUKS-encrypted root partition during boot using TPM and clevis.

Prevent service from swapping.

Disable swap at boot using systemd.

Allow users to access the kernel ring buffer and view the messages using dmesg.

Prompt for a login name on serial tty device.

Perform a system firmware update.

Inspect and alter BIOS settings through the command-line.

Alter port range available for automatic port assignments.

Automatically clear APT cache after each operation.

Perform DNS query by tracing delegation path from the root name servers.

Display release information using command-line.

Quickly list specific block devices.

Determine where exactly GRUB is installed.

This is a simple reminder that you can use basic system utilities to parse text files, extract, filter and concatenate data.

Inspect mount options for specific mountpoint or device.

Display systemd journal since system boot.

Display basic computer information using DMI table decoder.

Downgrade and keep specific package version.

Install fd as a simple and user-friendly alternative to find.

Configure Wake-on-LAN using systemd.

Create directory with defined ownership and permissions using a simple single-step command.

Inspect a path during the troubleshooting process.

Manage command history using text-based user interface.

Determine when package index was updated.

Install and configure chrony NTP server.

Display active but disabled systemd services.

Create an exception for a regular user to access service socket using systemd.

Configure persistent DNS resolver using systemd resolver or name server information handler.

Use Dynamic Firewall Manager to configure a basic zone-based firewall.

Noninteractively configure system locales.

Create a software watchdog for systemd service.

Determine fastest server using the Internet Control Message Protocol (ICMP).

Alter date format when listing cached Kerberos tickets.

Reload network configuration on Debian Bullseye.

Create and configure Virtual eXtensible Local Area Network interfaces.

Install the most recent kernel using experimental Debian distribution to see what is coming up.

Display systemd journal for specific service since it started.

Follow data appended to a file using one of the two possible approaches.

Determine when the service was started and stopped using the systemd journal.

Display when the operating system was booted and calculate uptime using the systemd journal.

Read QR Code from an image.

Generate QR code to access the Wi-Fi network.

How to provide custom TXT records in class 3 (CHAOS) using BIND9.

Specify the exact list of enabled PAM profiles using a simple workaround.

Configure SSH access using Samba Active Directory.

Use SingleFile to archive entire web page in a single HTML file.

Create Samba Active Directory server using Debian Bullseye.

Fix failed dynamic DNS update with Samba Active Directory and System Security Services Daemon by upgrading internal Samba DNS to BIND.

Determine fastest APT server using the Internet Control Message Protocol (ICMP).

Determine mountpoint filesystem type using core stat utility which is expected to exist on every operating system.

Install n³ a tiny and unobtrusive terminal file manager that will accompany you in your daily tasks.

Use nethogs utility to display current bandwidth grouped by a process

Delay the start of the systemd service at boot.

Colorize command output using grc a generic colouriser.

Perform basic operations on zip archives.

Use Docker or Pod Manager multi-stage build to compile Nginx from source code with additional headers-more-nginx-module module using Debian Bullseye image.

Install nala a human-friendly apt front-end using the python-apt API.

Handle low memory conditions on desktop using a nohang a sophisticated low memory handler for Linux in Python.

Keep a list of permanent ARP entries using the arp utility.

Configure and use LVM thin provisioning.

How to use tmpfs for temporary directory (/tmp).

Resize live tmpfs filesystem.

Use column utility to align simple MariaDB output like variable list.

Inspect and improve docker image using dive utility for exploring each layer in a docker image.

Install and configure a Kafka cluster without ZooKeeper to play with it.

Generate Kafka cluster ID for Kafka Raft metadata mode.

Relay all mail to an external account which can come in handy in your lab environment.

Debian Bullseye currently provides Samba 4.13.5. Using BIND as Samba Active Directory DNS backend opens it to the DNS zone transfer.

Pretty-print text files inside terminal using bat, a cat clone with syntax highlighting and Git integration.

Keep track of network latency using SmokePing on Debian Bullseye.

Use boot parameters to limit the number of available processors.

Install DNS lookup utility to perform basic DNS lookups.

Install Cluster Manager for Apache Kafka, previously known as Kafka Manager on Debian Bullseye.

Determine which SSH public key was uploaded to the web service.

Display IP address in a more readable format.

Create a basic Hadoop cluster to play with it.

Configure MariaDB server to log slow queries.

Use awk to parse apt history log and filter it.

Concatenate regular and gzip-compressed files at the same time.

Increase the maximum permitted number of simultaneous connections to the MariaDB server.

Load time zone tables into MariaDB server.

Log systemd service state changes using rsyslog.

Use date utility to display current date time in different timezone

Use systemctl to get process identifier for specified service.

Today I will extend the how to fix device excluded by a filter blog post to include information on how to wipe filesystem or partition-table signatures except for LVM2 members, which is a great idea for automation.

Write an operating system to microSD card using Raspberry Pi Imaging Utility.

Use system performance tools for Linux to display process statistics.

Manage systemd services remotely over SSH protocol.

Use sponge utility to read standard input and safely write it out to the same file.

Fix “device excluded by a filter” LVM error.

Create the simplest possible firewall using nftables framework with relaxed rules that will allow all outgoing traffic, incoming ICMP echo requests, and ssh connections.

Install Nexus Repository Manager (NXRM) 3.

Use templates inside shell scripts by substituting environment variables.

I have already described how to strace PHP-FPM processes, but you can also display a strace summary to get detailed information about count time, calls, and errors for each syscall.

Monitor file system events to restart service on every configuration change.

Use JUnit callback plugin to store and Allure Framework to visualize ansible playbook events.

Use numfmt command-line utility which is a part of the standard GNU Core Utilities to pretty print decimal or binary numbers.

Use varnishlog to log specific Varnish requests.

Varnish Shared memory Log can put a major strain on the disk (I/O write operations). The solution is to store it on the virtual memory filesystem.

Use needrestart utility to determine which services need to be restarted after the upgrade.

Install the Advanced Open Source Enterprise Wiki.

Use FUSE (filesystem in userspace) to access rdiff-backup repository.

Use AdoptOpenJDK/Eclipse Adoptium to install OpenJDK 8 (LTS)/OpenJDK 11 (LTS) or OpenJDK 15 (Latest) using Eclipse OpenJ9 or HotSpot Java virtual machine.

Execute rc.local shell script during boot using systemd compatibility generator.

Perform shell script analysis using shellcheck, a shell script static analysis tool.

Display packages that were installed automatically to satisfy various dependencies and are no longer required.

Calculate Elasticsearch’s average documents number in recent days using a shell script.

Use systemd service to automatically extend existing ext4 filesystem on boot or on-demand to optimize virtual machine configuration.

Retry Elasticsearch shard allocation that was blocked due to too many subsequent allocation failures.

Calculate Elasticsearch hit ratio using command-line curl utility.

Delete old Elasticsearch indices using Elasticsearch Curator utility.

I have already described how to accurately determine when the system was booted, but there is a simpler solution as you can use /proc filesystem directly.

Update the docker-compose configuration file to reduce the container log file size before you run out of disk space.

Specify a custom SSH port when using rdiff-backup.

Create swap file to optimize virtual machine configuration or just immediately increase available swap space.

Extract a specific file from a tar archive.

Automatically clear GNU Bourne-Again SHell history when you exit a login shell.

Inspect parent processes to determine whether shell script or specific process has been executed locally, remotely, or by any other application.

Determine whether the standard input file descriptor refers to a terminal which can be useful to ensure that the shell script is executed using an interactive terminal.

Display default Elasticsearch settings.

Limit bandwidth on specific network interface using wondershaper.

Test TLS/SSL encryption anywhere on any port

Query and change the system hostname.

Keep track of network latency using SmokePing on Debian Buster.

Inspect RabbitMQ settings using command-line.

Use basic linux command-line utility to calculate real disk capacity.

SmokePing 2.7.3 needs an update to use the SSH probe on Debian Buster.

Determine available authentication methods on the specified OpenSSH server.

Create custom Bourne Again SHell package to disable network redirections and enhance system security.

Use templates to define default Elasticsearch index settings.

Undo fsck operations performed on the Ext4 filesystem.

Reindex directories located in the Ext4 filesystem after removing a huge number of files to optimize directory sizes.

Use simple HAProxy configuration hacks to serve a single static file.

Merge multi-process HAProxy statistics using GNU Awk. This is a duct tape solution, as you should definitely use Lua.

Merge multi-process HAProxy statistics using Lua.

Distribute messages to different RabbitMQ node using federation plugin.

Move messages to different RabbitMQ node using shovel plugin which acts as a simple client.

Copy messages to different RabbitMQ node using federation plugin.

Find out whether remote port is open using Bourne Again SHell network redirections.

Mirror RabbitMQ queues cluster to replicate configuration across multiple nodes.

Create RabbitMQ cluster to replicate configuration across multiple nodes.

Display active Elasticsearch searches and calculate average value.

Use rabbitmq_top plugin to display RabbitMQ Erlang processes.

Unmount not accessible NFS share that still has open files.

Log every executed command to syslog.

Install CouchDB on Debian Buster.

Use RabbitMQ Management API to export or import configuration.

Reset RabbitMQ node configuration.

Generate password hash for CouchDB administrator.

Display RabbitMQ/Erlang version using essential utilities.

Use OpenResty to perform health checks in your cloud environment as it incorporates Nginx, Lua and comes with batteries included.

Ensure that specific service is started after the system time has been synchronized.

Specify systemd startup timeout option to prevent service start operation from timing out.

Generate password digest for basic authentication of HTTP users.

Modify systemd service configuration by using drop-in files, which is useful for automation when using ansible or any other provisioning, configuration management, and deployment utility.

Perform basic Elasticsearch 7.x operations.

Install Elasticsearch 7.x on Debian Buster.

Instruct Ansible to use a specific version of Python interpreter on the remote host.

Node name is by default part of the location where the RabbitMQ data is stored, so you need to explicitly define static location to ensure that RabbitMQ data is always available in these rare cases when there is a possibility of node name change.

Specify RabbitMQ node name to use your own prefix or particular hostname.

Use HAProxy stats socket to determine current application status.

Access your files stored in OneDrive using rclone command-line program to sync files and directories to and from cloud storage and FUSE Filesystem in Userspace filesystem.

Suppress message of the day for specific or multiple users.

There are use cases where you need to know which backend server is used, so use a specific header to send the target server name to the backend.

Manage and display system news using a simple but effective utility.

Handle domains that are not defined in the configuration using dedicated backend.

Visualize the blog schedule using a terminal.

Display LWN news using the message of the day framework.

Install Restyaboard, an Open Source Kanban board.

Protect the operating system against accidental shutdown or reboot.

Display message of the day after successful login.

I have already described how to create VLAN interface, but things have changed over time, so I decided to update the know-how.

Get and display RabbitMQ uptime measured in seconds using three different methods.

Install RabbitMQ message broker to queue and exchange messages.

Use dedicated command-line utility to convert various units to different measurement systems.

Use drctl-tools to parse Debian package information using the Debian control file format (the dctrl format).

Use wcs stream meter created by Arno Wagner to display count and rate statistics for data read on standard input.

What does “Release file for […] is not valid yet (invalid for another […]). Updates for this repository will not be applied.” error mean?

Isolate the problem and strace multiple PHP-FPM (FastCGI Process Manager for PHP) processes to identify the culprit.

Define default Firefox settings to always use your preferred configuration.

Create persistent sysctl configuration using standard system utilities.

Quickly fix fusermount: exec: "fusermount": executable file not found in $PATH by installing missing Filesystem in Userspace package.

This is an extension to an older blog post on how to mount WebDAV share using systemd as this proved to be a very reliable method that is easy to mark as a dependency for other services.

RabbitMQ uses Bintray to provide official repositories for RabbitMQ message broker and Erlang, but there is a small catch as at this moment repository for Debian Buster does not contain RabbitMQ application…

Modify system identification message that is printed before the login prompt.

Update the system time using systemd as a NTP client.

Create Argo Tunnel to expose internal service and securely access it over the internet.

You already know how to collect and report system activity information, so it is the best time to learn how to export already collected data.

I have recently updated Debian Buster from testing to stable, so it is worth to note how to perform such update non-interactively.

Use netstat, ss or files inside proc filesystem to count TCP connections.

Generate and print sequences of numbers to perform specific operations using command-line or shell script.

Create a shell script to determine how long a specified remote server or device was offline. It is not designed to substitute monitoring solutions but to determine how long it will take to reboot the server or device. It is using convert seconds to human readable time code to display results.

Configure sysfs during system boot to apply custom configuration in a simple and convenient way

Increase Google Cloud virtual machine instance disk size without service interruption.

There are certain situations where I disable Intel Turbo Boost, for example to keep fans quiet during the night time.

Enforcing your own security policy that defines users, SSH keys, and sudo configuration inside custom templates based on official images in Google Cloud requires that you disable Google Accounts service, so it won’t get in the way.

Collect and report system activity information using sysstat a system performance tools for the Linux operating system.

Check website for broken links using HTTrack website copier.

Copy website for offline browsing using HTTrack website copier.

Pretty print size in bytes using AWK.

Download OpenVPN configuration using public NordVPN API to specific file.

Display memory used by processes in human readable form using Python script.

These are easy mistakes to make as the bash builtin read command will terminate with the error exit code on the end-of-file condition and use Internal Field Separator to split the line into words. It is kind of tricky, but it is worth knowing how to deal with such problems.

Display memory used by processes in human-readable form using ps and awk utilities.

Manipulate X clipboard from terminal using xclip utility which is a command line interface to X selections to easily copy and paste text from terminal to GUI applications.

Display your external IP address using public NordVPN API.

Learn how to free dirty objects, page cache, and reclaimable slab objects for troubleshooting or instructional purposes.

Today, I will show you how to get and display user details using a shell script. This work is based on a Python-based solution by David Green and located at bitbucket/nordapi.

Sometimes it is very convenient to define shell function and execute it remotely.

Perform a dictionary attack on the forgotten LUKS passphrase to access the encrypted device.

Compare two files byte by byte using cmp file comparison utility.

Inspect Redis internals using UNIX socket and Python script without external dependencies.

Use simple shell function to instantly create known_hosts entries for specified host, including its IP address and remove outdated public host keys.

Global known_hosts file located in /etc/ssh/ssh_known_hosts and user managed ~/.ssh/known_hosts contain known host public keys. Due to its nature these files can contain multiple entries using the same key. It is not a problem, but merging entries using the same key is the first step that is necessary to inspect it visually and to verify host entries.

Disconnect idle SSH clients using built-in client alive mechanism.

Learn how to erase the LUKS header on a specific device.

Monitor PHP-FPM (FastCGI Process Manager) pool using curl utility, cgi-fcgi application or slightly modified Python script that was used to display PHP-FPM pool information.

Discover two distinct and easily scriptable methods and combine features from both of these to locate and identify LUKS devices.

Display PHP-FPM (FastCGI Process Manager) pool information using UNIX socket and Python script. I thought it would be easy to write a simple FCGI client. Apparently not, but it was an exciting and rewarding experience.

Learn how to test LUKS passphrase on a specific device.

Display PHP-FPM (FastCGI Process Manager) pool information using command-line utilities like curl or cgi-fcgi.

I have already described how to check external IP address using curl or your own SSH service, but you can also use dig utility to take advantage of the OpenDNS, Google or Akamai DNS service.

Determine maximum LUKS key file size or maximum interactive passphrase length.

Use the find utility to move files based on specific time criteria.

Learn how to create and assign binary key instead of passphrase to LUKS key-slot on a specific device.

I am surprised that exFAT is not supported out of the box as it is a default filesystem used on SDXC cards. You need to install a FUSE-based implementation to access data on devices using it.

Learn how to non-interactively manage LUKS passphrases on a specific device using files or a named pipe.

In a blog post a month ago, I described how to use a terminal to display servers recommended by NordVPN, but the same result can be achieved by using public API service. It is not officially documented, so let’s play with it.

Determine what filesystem is mounted where, what is using particular options and how much free space is available.

Learn how to interactively manage LUKS passphrases on a specific device.

Use NordVPN command-line utility to easily manage VPN service.

The simplest possible way to create a Debian package is to use defined package metadata and prepared target directory structure.

Control the amount of information printed out to standard error by the dd utility.

Verify static filesystem information defined in the fstab file after applying modifications to ensure that system will boot without any problems. It is especially important in remote locations or places where you cannot easily perform emergency operations.

Learn how to erase every defined LUKS key slot on a specific device.

I have already described a simple way to manually configure Network Manager and automatically import NordVPN servers, so today, I will explain how to pretty print servers recommended by NordVPN using terminal instead of web-browser.

Learn how to create LUKS header backup and restore it in case of emergency.

Create a shell script to convert seconds to human-readable time. I have reused part of an old shell script used to pretty-print system uptime to build it, as this code proved to be useful on several occasions.

cal is a nice utility that displays a calendar in the terminal, but there is a small problem that needs to be fixed as it uses Sunday as the start of the week.

Very rarely and often by mistake, you can end up with a deleted file that is still used by some process, which is likely writing to it, so the used space cannot be freed.

Install Prosody, an Open-source and modern XMPP communication server.

Sometimes it makes me wonder whether I am inside a chroot environment or not, so let’s check it out.

Define backup backend in HAProxy configuration to choose used backend depending on the number of usable servers.

Schedule a one-time task at a specific time or below defined system load using at utility.

Alter password expiry date to force user to change password on next login.

Execute paste utility to merge lines using tab character as a delimiter, expand to convert tabs to spaces, and column to format input into multiple columns.

Display processes using the most CPU or memory using nothing more than basic Linux utilities.

Encrypt portable external hard drive using Linux Unified Key Setup to protect data in transit.

Create simple artificial package to work around missing dependencies.

Create straightforward shell script to resolve hostname to IPv4/IPv6 address and reuse parts of it for other projects.

Use a shell script to count separate line entries inside a pipe to see how many entries got filtered out. It can be useful in some scenarios, especially for testing.

Verify package contents by hand or use simple shell script to automate this process.

Recently, I have parsed logs of several applications to generate custom weekly reports. It was a fascinating exercise.

I have already described how to list the contents of specified package using apt-file utility, but you do not need it to check the contents of downloaded package.

Create the simplest possible meta-package to install multiple software packages at once and quickly set up a familiar environment.

Make iptables configuration persistent using systemd file with additional possibility to disable firewall after defined period of time.

Display reverse dependencies to inspect which packages depend on given application or library.

Make iptables configuration persistent using custom service file with additional features like configurable wait time, so you can safely interrupt execution and test mode that will disable firewall after defined period of time.

I have already described how to copy answers to the configuration questions for Debian packages, but there is an easier way to read and insert new values into the debconf database.

Perform simple incremental backup using rdiff-backup utility.

Make iptables configuration persistent using essential system utilities or a designated boot-time loader.

There are those rare situations where you do not know the public key required to verify repository signatures but want to add a repository and a public key used to sign it. Hopefully, there is an easy answer to that question.

Install and configure localepurge package, which provides a fancy shell script to recover disk space used by useless localizations.

Install and configure Dashing with Icinga 2 to use the external board for your Icinga2 instance.

Use Content-Disposition HTTP response header to determine filename and use it to store downloaded file.

Delete Nextcloud bookmarks using API. Notice, data is paginated in this case, so this particular case is more interesting than regular add/remove operations.

Reset admin password on UniFi controller to access wireless configuration.

This technique is widespread. To be honest, it is more common than I initially thought, so I will show you how to create a single shell script that will display, create or destroy a temporary file system depending on the name used to execute it.

Configuring and using additional repositories requires APT public key management to validate the Release file and downloaded packages.

Find a symbolic link by the target name. It sounds simple and it definitely is.

Log dropped connections from iptables firewall using netfilter userspace logging daemon for further analysis and troubleshooting.

Determine how long it would take to copy data between directories.

Verify file integrity using the GnuPG signature without touching your local GnuPG configuration.

Compute SHA message digest of a file to verify that its contents have not been altered.

Create a shell script for a cron job with hidden debug information shown only when executed inside the terminal.

Use find and grep commands to search for directories that contain one or multiple files with specific content.

Log dropped connections from iptables firewall using rsyslog for further analysis and troubleshooting.

Display dependencies to inspect which packages are required for a given application.

Enable HTTPS (Hypertext Transfer Protocol Secure) for package managers using libapt-pkg library.

Whitelist or render inoperative any USB device to secure your personal belongings.

Create an iptables firewall using custom chains that will be used to control incoming and outgoing traffic.

Display upcoming events in the Nextcloud calendar using a custom shell script by extending the earlier ideas.

Create an iptables firewall that will be used to control incoming and outgoing traffic.

Display upcoming events in the Nextcloud calendar using a text-based terminal emulator because it is fun and challenging.

Dynamically choose HAProxy backend depending on the HTTP host header, Lua programming language and environment variable.

Detect and log changes in the list of mounted filesystems (/proc/self/mountinfo file).

Use GNU Bourne-Again SHell builtin or standalone time command to determine process execution time.

Use cron service to execute additional commands as the specified user during system startup.

Recently, I have moved my personal source code to GitLab. It rendered self-hosted git repository at repository.sleeplessbeastie.eu obsolete, so I have created simple redirection on HAProxy load balanced to cover this specific case.

I am using the lightline status line with the Solarized color scheme inside Vim text editor.

Store LeaseWeb data traffic in OpenTSDB time series database using Python script, LeaseWeb API v2 and Python client to OpenTSDB.

Serve files from memory with a fallback using the Nginx HTTP server.

Create the simplest possible iptables firewall with quite relaxed rules that will allow all outgoing traffic, incoming ICMP packets, and ssh connections on the eth0 interface.

I am currently playing with floccus to store bookmarks using Nextcloud, so I have created simple shell scripts to import Nextcloud bookmarks from Firefox using code from my earlier solution to open Firefox bookmarks from the OpenBox menu.

Define and use a variable to dynamically choose HAProxy backend depending on the URL parameter, HTTP header field, and cookie value.

LeaseWeb released a new version of API that will deprecate the old one, so it is the perfect time to update the Python script using v1 api and switch to API v2 before May 31.

Use kernel automounter to automatically mount directory shared over network using NFS.

Use Unsplash Source a simple API for embedding free high-resolution photos from Unsplash to get background for DokuWiki instance. Source code is hosted at GitLab/unsplashdoku and documentation is available on the main DokuWiki/plugin:unsplashdoku website.

There is a bookmark manager for Nextcloud that can be used with the floccus browser extension to synchronize bookmarks using Chrome, Firefox, and Opera. I will show you how to perform API calls to automate the backup process.

Set up a simple Docker registry to use it privately or share images with a team of developers.

Create a base Docker image using debootstrap utility.

Securely change user password using shell script to automate this task on these rare occasions.

I have described the differences between the old and new free output format, so now I want to mention how to execute the former free version on Debian Stretch using LD_LIBRARY_PATH environment variable to temporarily substitute a different library for this particular execution.

Use the extensive API offered by the Restyaboard to backup and restore created boards.

Install docker on Debian Stretch to take advantage of the lightweight virtualization.

The truth is that I always return to the DokuWiki to organize personal data, so I have created small calendar as a plugin to perform daily notes. Source code is hosted at GitLab/monthcal and documentation is available on the main DokuWiki/plugin:monthcal website.

Block particular IP addresses on HAProxy load balancer using simple Access Control List.

Upgrade icinga2 and its web-interface using official/dedicated repository and PostgreSQL database.

This is just another interesting problem to solve. I have encountered this subtle difference in PHP packages when I moved personal Dokuwiki instance from Debian Jessie to Debian Stretch.

Install Restyaboard, an Open Source Kanban board. I am using it daily to manage this blog.

Use essential openssl utility to quickly determine if your web-server still supports deprecated TLS 1.0 protocol.

Define basic authentication on HAProxy load balancer to limit access to specific backends.

Use dpkg to pretty print package dependencies.

Define allowed HTTP methods on HAProxy load balancer using simple Access Control Lists.

Use encrypted passwords to automatically set up users using configuration management tools like Puppet or Ansible.

Create custom data field to define multiple domain names and service apply rule to verify those SSL certificates.

Debian Wheezy provides an ancient version of pip utility for installing Python packages. To put it very simply, it does not work anymore as it is not using HTTPS protocol, but fortunately this issue can be quickly fixed.

Install the UniFi controller to configure a wireless network using Ubiquiti devices.

Icinga2 documentation clearly describes the master->satellite->client setup, but as of now everything can be configured using the director module and a top down approach, so you can easily monitor external remote networks that are not accessible from the master server.

The free utility is used to display the amount of free and used memory in the system. Debian Stretch provides an upgraded package. The output format has changed, and available memory is calculated using a different method, so let’s see what we can do with these modifications at this moment.

Alteration of the software RAID arrangement often requires an update to the boot configuration of the mdadm utility for the management of Software RAID.

Add your first host using icinga2 director after performing clean installation as I have described earlier this month – icinga2 plus icingaweb2 and director module installation procedure.

Icinga is a great monitoring solution, especially when you use the director module to perform configuration in a top down environment. It makes the application more accessible to more people as you can use the web-interface and role-based permissions to allow developers and testers to write and use their own checks and notifications.

Install Icinga 2 monitoring instance with web-interface.

MariaDB unixODBC driver is not available in the Debian package repository at this moment, but you can build and configure it on your own. It requires some additional work, but in the end it is really worth the time.

Query APT configuration to inspect specific options or create universal Debian utilities.

It is very useful to know how to distinguish between different GnuPG public key files.

There are many different ways to verify IPv4 address inside a shell script, but many of these are complicated or incomplete. I will describe a simple and verbose way to check IPv4 address using ipcalc utility.

Debian supports DES, MD5, SHA256 and SHA512 algorithms for password encryption. These algorithms can be easily spotted and distinguished by their structure.

Display IPv4 network information for given address and netmask. Split networks, calculate subnetworks and supernetworks and convert address range.

LeaseWeb provides an API that can be used to request information about servers and perform some maintenance tasks like update reverse DNS entries, null route IP addresses, reboot specific server or launch rescue/reinstallation process. I will show you how to request and display identifiable information about servers in each location including data traffic details.

I am using a simple shell script to manage OpenSSL known_hosts file as it requires many small updates due to constantly changing host keys on a dynamic virtual server.

Backports repository provides packages for stable system that are recompiled from testing or unstable distribution. It is important to know that these packages are provided as is without any security support guarantee.

Debian Stretch provides gnupg in minimal installation as the package priority is set to important. The command is fully operational, but it requires dirmngr to perform network operations for managing and downloading certificates.

Remove package dependencies that are now no longer needed and configure the system to perform this task automatically.

The init-system-helpers package that provides a helper tools for all init systems is not available in primary Debian Wheezy repositories. You need to use wheezy-backports repository to install it on that operating system.

Keeping an eye on a constantly changing APT cache can be quite tedious, so automate this task and free up your time to focus on other projects.

This is just a brief note on how to reverse a text file. It is not really useful for anything other than fun, but it is stuck in my head, so I need to write it down.

Clear the APT cache to reclaim disk space used by the downloaded packages.

Disable APT cache to conserve disk space on a small Debian based embedded system or a custom-built live USB system that can be easily booted.

You can check my earlier blog post on how to mount WebDAV share using command-line or fstab (file systems table), but you are not limited to these two options as you can use systemd to take care of the whole process and automount WebDAV resource on demand.

I am an enthusiast of the uWSGI project. You are still not limited to it as you can use fcgiwrap, a very lightweight and straightforward FastCGI wrapper for CGI scripts that do not require additional configuration.

Keep track of network latency using SmokePing, uWSGI application server, and Nginx HTTP server. SmokePing supports many configurable probes, alerting, and live charts accessible through a web browser. It was created by Tobi Oetiker, which is known for RRDtool an Open Source data logging and graphing system for time series data.

Nextcloud is a handy self hosted web-based application that can be used to store files, contacts and calendars. It provides the desktop and mobile client. In addition, it supports Web Distributed Authoring and Versioning protocol, so let’s mount a WebDAV share.

Install and configure a private instance of the MoinMoin wiki engine, a full-featured and extensible wiki software written in Python that can store personal notes, knowledge base, or simply share interests.

You can connect custom-built shell script with any database using unixODBC an implementation of the Open Database Connectivity standard and I will show you how to do this for SQLite and PostgreSQL databases.

It is rarely mentioned, but you can use repository snapshots to download and install old and obsolete packages on already unsupported or even current Debian distributions.

Use Python script to verify that client can connect to the RabbitMQ message broker.

I have a feeling that loop devices are now used less frequently, but these are still relevant and useful.

HPE Software Delivery Repository is cryptographically signed, so you can be sure that provided software packages have not been modified by a third party. However, sometimes you can encounter the The following signatures couldn't be verified because the public key is not available error which can be easily fixed.

Stop running away from this, request and assign an IPv6 address to an external interface to make content available over both IPv4 and IPv6.

Two years ago, I described a simple way to display established TCP connections using ss command. Today I will use lsof and gawk to pretty print network connections.

Build your first VServer on Debian Wheezy using psand.net public repository.

It is a matter of personal preference whether you use current or former network device naming convention. I am more accustomed to the latter and will configure the operating system to retain the old behavior.

ifconfig is not installed by default in Debian Stretch. However, it is available in the package repository, so applications that depend on it can still be used.

Use s3cmd Command Line S3 Client and Backup for Linux and Mac to display disk usage on a particular bucket.

Recently I stumbled upon the missing firmware for Broadcom Tigon3 based gigabit Ethernet card after kernel upgrade process. Simple problem, which was solved by installing firmware-linux-nonfree Binary firmware for various drivers in the Linux kernel package.

List configured APT data sources for binary packages using apt-cache utility.

There are rare cases when known hosts file becomes corrupted, so basic ssh utilities fail within custom built shell scripts due to ~/.ssh/known_hosts is not a valid known_hosts file error.

There are circumstances when you want to ensure a particular package version during the setup process. I will show you a simple method to verify the package version suitable for sourcing into a shell script.

There are at least several ways to determine when the process was started to help you investigate and trace potential issues. I will briefly introduce four different methods to choose the most useful one.

There are many applications that share the same source package, so I will show three different ways to print the name of the source package.

Knowing how to determine the last time package index files were updated can be beneficial when you least expect it. It is not something used every day but can be used to monitor or verify when apt-get update command was executed.

It is very easy to upgrade the whole Debian system, but you can also upgrade only selected packages and skip the rest.

Many years ago I wrote How to display available updates blog post which mainly related to Debian Wheezy. Today I want to extend it by a neat console friendly utility available in Debian Jessie since the milestone apt release thanks to Michael Vogt.

I have already presented an easy way to build Vagrant Debian base box using qemu, but on some platforms it is better to use VirtualBox as it is not possible to use kvm accelerator.

It is time to look into the build process of Debian Vagrant box, create one using packer utility for creating machine and container images and alter the whole process a little bit.

I am constantly moving between a fixed list of several directories daily. Using cd can be tedious at times, so I defined a shell function to quickly jump between a defined set of directories.

Vagrant is an awesome piece of software, but constantly downloading system packages can be very time-consuming. The simplest solution is to set up an apt caching proxy as a Vagrant box.

Today, I will publish Vagrant configuration to set up DokuWiki instance. It is just a handy reference, as described in the earlier blog post.

Today I will install Vagrant which provides an easy way to configure reproducible and portable virtual environments. It is just a first step towards this new direction, so stay tuned for more details soon.

I have already described a straightforward way to automatically login user at the console without touching the graphical user interface using Debian Wheezy, so today I will post an update for Debian Jessie as the whole process has changed considerably.

Dokuwiki is the best Open Source project I have ever used, so I have prepared a simple step-by-step guide to help you get started. It is relatively brief and concise as most of the code was already described in other blog posts found on this website.

I have described a simple way to configure the AWStats web-interface last month, so I will continue this topic further and tell you how to add a menu to quickly switch between configured sites.

Today, I will illustrate a simple way to check for specific command inside a shell script, which is quite simple as it uses only shell built-in command utility.

Today, I want to briefly describe a simple way to check for a specific package inside a shell script.

I will show you how to configure the AWStats web-interface using the uWSGI application server and Nginx HTTP server, which is a very simple and straightforward process.

It is easy to get names of distinct Debian releases as you can always examine these on the Debian Releases web page. I will do something more interesting and demonstrate how to do that using a simple shell script.

This brief outline explains how to locate specific file within Debian packages using very useful apt-file utility which as opposed to dpkg-query does not only inspect installed packages since it utilizes fetched lists of the contents of packages.

I will show you how to generate a random password using the OpenSSL utility, standard command-line utilities, Password Generator (pwgen), and Automated Password Generator (APG).

It was recently pointed out to me by Piotr Gabryjeluk that Iceweasel name was dropped (see Debian Bug report #815006). This caused a major inconsistency in the previous blog post. This is an updated version for Debian Jessie

Today, I will describe how to cause PostgreSQL clusters to reload their configuration files using four simple methods.

Since the beginning of this year, I have started using Seafile, and I absolutely love it as it offers simple data organization using libraries and reliable file synchronization between multiple devices with built-in encryption. Check for yourself as it is undoubtedly worth it.

This blog post is an update to the earlier PostgreSQL entries in which I will show you how to use continuous Write Ahead Log archiving to take advantage of the point-in-time recovery.

I have already described a simple way to perform base PostgreSQL backup using file system utilities. Now I want to show you a different approach using pg_basebackup utility.

It is an interesting thing to know how to parse and process Linux Software RAID events. It is also beneficial as you can automatically take appropriate action immediately after a certain event occurs.

Today I want to show you how to perform base PostgreSQL backup using standard file system utilities. It is a great example as it briefly describes basics required before moving to more advanced topics.

There are many different ways to set NOOP scheduler on the first hard drive at system boot. I have decided to use simple systemd service, but alternatively you can use udev to automatically configure every SSD device (see References section).

Sometimes, I want to prevent regular users from logging into the system to perform more complex operations. To achieve that, I am using Pluggable Authentication Modules for Linux to temporarily disable user logins.

This is a follow up to the previous article. I will briefly describe a way to boot Debian installation ISO image from USB flash drive using syslinux bootloader.

Today, I will show you how to create customized USB flash drive to boot selected ISO images using Syslinux bootloader for Linux ext4 filesystem. It is very handy and useful, so let’s begin immediately.

It is a short entry, but a useful one, as it is important to have a basic knowledge of how to schedule system reboot or power it down automatically at specified time.

Do you want to use the latest version of Iceweasel, also known as Firefox? Then add the repository provided by the Debian Mozilla team and choose between release, beta and aurora versions. This blog post is obsolete. Please read How to use a recent version of Firefox in Debian Jessie instead.

Recently described hddtemp application does not contain every possible hard drive in its database. I’ll be honest here, its development stopped many years ago, but it is still very useful, so I will shortly describe how to add new hard drive to the database.

It is often overlooked that hard drives which are available on the market provide temperature measurements. This temperature can be effortlessly monitored using hddtemp application by Emmanuel Varagnat.

It is possible to install Debian over the network with a little help from another person in a remote location. I performed it only once and it was some time ago, but the whole procedure is quite easy and straightforward.

There are times when it is handy to know how to create shadow directory of symbolic links. I am thinking in particular of the software compilation process, as I have used this technique in very distant past to build X Window System.

It is very easy to add users by hand, but sometimes such actions needs to be automated.

Two years ago I have described three simple ways to determine whether the processor supports 64-bit instruction set. Today, I will show you how to determine whether any Debian-based operating system is 32-bit or 64-bit.

I have successfully used Google Drive and Insync to organize all of the e-books that I have acquired during the last years. Currently I plan to upload them to a personal DokuWiki instance since I use it more every day. Before I can start, I need to extract cover images to ensure that I will get a decent outcome.

Today, I will explain how to automatically choose nearest mirror based on geographic and network location using Debian mirrors HTTP redirector to solve the common problem of choosing an appropriate mirror.

I had an unexpected incident last week as one of the hard disks in my server failed. This device was a part of a software RAID mirror, which created an opportunity to describe the whole process.

Maybe it is rarely needed, but recently, I found it very useful to know how to record an interactive session, so I could reference to it later or just examine it further.

It is easy to lock the screen when using any of the available desktop environments or even basic X Window utilities. The more interesting thing is to achieve the same functionality on a text-only based system.

A week ago I wrote about a couple of interesting applications that can crack passwords, but they were not as fast as I thought. After investigating this topic further, I ended up using a community-enhanced version of John the Ripper.

I have recovered old backup only to learn that I do not remember password to the found archive. As a result, I checked out two command-line applications to crack passwords used to encrypt zip, 7z or rar archives.

Today, I will show you how to put every connected USB storage device in read-only mode using udev dynamic device management, blockdev utility, and systemd service unit configuration.

Human memory is sometimes unreliable, so it is not always possible to answer in the same way to the configuration questions. Fortunately, this process can be automated using debconf utilities.

Debian Jessie is using systemd as the default system and service manager. I will not argue about it, but instead, I will briefly introduce the whole thing.

I have already described chkconfig utility in CentOS – How to manage system services blog post, but today I want to mention that you can also use it to manage services on Debian Wheezy.

I have already written a couple of posts about software RAID setup and recovery. Today I will briefly describe how to switch array to read-write state and begin resync process.

I often want to omit data from certain tables during PostgreSQL database backup. Today I will look into this and post my findings for further reference.

Several months ago I have shortly described how to close a non-responsive ssh session, which comes in handy at times. Today I will describe how to close every active ssh session by inspecting existing pseudoterminals.

I have unexpectedly experienced an issue with a couple of broken packages, which was easily solved using debsums utility.

Today I would like to tell you how to search for files by date, which is a very useful skill when you spend most of your time on the command-line.

I want to automatically log out the user from the login shell after a defined period of inactivity but leave X Window Terminals untouched. This will allow me to enhance security slightly, as I will not accidentally leave the superuser session running for a long time.

When managing large datasets, it is remarkably easy to end up with orphaned files, those without an assigned owner or group. These files can persist unseen, potentially creating security vulnerabilities or just contributing to system clutter. Fortunately, the find utility provides a direct method to locate them.

I often want to save a recently executed command to the personal log file for further reference, so let’s do it.

On Sunday 29th April 2012, I have described How to check dd’s progress using User-defined signal 1. Today, I will extend this topic further using the proc filesystem.

Using find command is not always the fastest way to search for specific files. The better method is to use mlocate utility, which uses its own file database and provides only user-accessible results.

Sometimes I want to inspect and verify queries made by an application or hunt a bug that involves more complex queries. The essential part of this process requires altering PostgreSQL server configuration to log SQL statements.

Simple shell script that will iterate through the directories in the PATH variable and print only files identified as scripts.

I am constantly on the move, so sometimes I need to quickly verify my external IP address, as I do not want to accidentally block myself on some kind of firewall.

I always asked myself how to password protect GRUB entries on an encrypted notebook to lock down the boot loader and protect it from unauthorized access.

I have been using unattended upgrades on development machines since the end of last November, when I installed Debian Jessie release.

It is well described how to verify file existence or type, but there is much more information that can be easily verified inside shell script using nothing more than simple stat command.

I have updated my desktop computer to Debian Jessie. After that I quickly encountered an issue with GNOME Terminal, Midnight Commander and already assigned F1 and F10 function keys.

Sometimes I want to access a private server at home from a different network while being on the go. The easiest way to do this is to use autossh utility to create a secure and persistent reverse SSH tunnel to the publicly available server.

Do you want to use the latest version of Iceweasel, also known as Firefox? Then add the repository provided by the Debian Mozilla team and choose between release, beta and aurora version.

Sometimes I need to check the installed package version, compare it with the available version, or verify that the correct version is already installed. I will show you how to quickly perform these checks.

Default Debian installation does not include VPN support inside the Network Manager applet. The reason behind this decision is probably the variety of available solutions.

Take control over configuration files and store them in version control system using etckeeper utility created by Joey Hess, which seamlessly integrates with package management tools inside Debian operating system.

Today, I will briefly describe how to automatically share X session on Debian Wheezy using VNC protocol.

Since Debian Jessie installation, I have encountered Hangcheck timer elapsed error. It is a really nasty bug as the only way to escape frozen X Window System is to reboot the whole operating system.

Today, I tried to visualize how many processes each user is running using a bar chart. The catch is that I want to see results in a plain terminal, which makes things more interesting.

Yesterday, I left a long-running copy process between two external USB hard-drives. I did not want to assume anything, so I created a simple shell script to ensure that the whole process went smoothly.

I have already written a blog post about useful Bourne Again SHell key sequences, so today, I will touch on another important aspect of the daily routine – the history.

Recently, I was searching for an easy to manage VNC service to use it at home. After a short while of consideration, I decided to install TigerVNC and manage it using Monit.

The default interactive shell in Debian is Bourne Again SHell, so it is worth to invest some time to at least skim through the available readline key sequences to gain higher proficiency at the command-line.

Recently, I noticed “Failed to save changes” error when I tried to move events between distinct calendars. After a short investigation I found that this bug is already fixed, but not packaged for an easy upgrade, so I will shortly describe how to apply fix for Debian Wheezy and Kolab 3.3.

Not well documented, but a quick and simple operation.

I had a little experience with multi-touch devices, so I was happy to use for a while iiyama TF2234MC multi-touch monitor with Debian Wheezy. It was quite a pleasant experience with a little bit of adventure.

It is a very simple operation that can be effectively used inside shell scripts.

There was an interesting change in the tasksel announced on the October 5th, 2014, as it provides an opportunity to choose desktop environment during installation process.

I have been using self hosted Kolab Groupware everyday for quite a while now. Therefore the need arose to monitor process activity and system resources using Monit utility.

This weekend I encountered a simple, but interesting topic, which concerns comparing the contents of two directories. The fun part is that you don’t need any additional utilities as standard diff command is fully sufficient.

During my recent activity I have noted to check out how to extract an ISO image in a traditional way using only shell utilities. It turned out to be easier than I thought, so I will present you three different solutions.

Debian was founded exactly twenty-one years ago by Ian Murdock, you can even find original newsgroup subject New release under development; suggestions requested.

Recently, I have encountered an interesting issue, as I could not perform specific database operations due to unwanted and active sessions using the database. Thus, I will briefly note the solution for further reference.

This weekend, I have spent some time investigating SSL certificate-based authentication and implementing it in Kolab web-based user interface. This topic is fascinating but definitely too broad to be briefly described in a single blog post, so do not look at it as a complete solution, but treat it only as a proof of concept.

Today I have found an interesting issue as I tried to forbid shell script execution from different directory.

After a longer period of time, I have decided to install Kolab and use it as a personal information manager. The installation process went as expected until the setup process tried to install the Roundcube database and failed miserably.

Currently, I am working over an unstable network connection, so my SSH session is constantly disconnected. It is a very uncomfortable situation as a dropped SSH connection freezes the whole terminal.

You may have noticed that I became a fan of solarized color palette by Ethan Schoonover used for terminal and gui applications. You will therefore not be too surprised when I describe how to install it and use in Emacs text editor.

I have discovered org-mode in the last year but have been using it for the last two months with increasing enthusiasm and commitment. I will be honest and tell you that it is the sole reason to learn and use Emacs on a daily basis.

Today I needed to archive every non-hidden directory in several different locations. I do not like to repeat myself so after a while I quickly created a shell script to accomplish this task.

It is not a secret that I am using Gandi Simple Hosting to host sleeplessbeastie’s notes website. This solution is almost maintenance-free and does not require any additional work to use Jekyll, as hosting static content is dead simple (see shell script to automate build and upload process).

Recently I was asked to reset root password on some long forgotten Debian box. It was an easy and straightforward task, but, as there are some interesting pitfalls, I will describe the whole process of acquiring root shell without password using single-user mode and a couple of ways to prevent it.

I am used to installing Debian using a minimal CD, however, I always forget to download it in advance, so I need to take a note and store its location here for further reference.

If you are wondering how to count only local users ignoring system accounts, I will give you a concise and straight answer.

Today I will shortly describe how you can remotely check the PostgreSQL version and use it inside shell scripts. This ability comes in handy at times, as it can be used to perform different tasks depending on the returned database version.

Today I want to install Debian on an older but quite capable Dell machine so I will shortly describe how to set up a KVM full virtualization solution.

There are plenty of off-line Debian systems just waiting to update index files, upgrade or install additional packages. This can be easily achieved by using apt-offline utility. I will shortly describe a common usage scenario as it is a very handy application.

The easiest way to reliably use Serial port within the local network is to use RS-232/422/485 NPort Device Server produced by Moxa company. I will shortly describe how to install NPort 5110 (1-port RS-232 serial device server) on Debian Wheezy.

I am using Jekyll to generate this website for half a year and Gandi for an even longer period of time so at the beginning of this year I revisited How to quickly download or upload directory tree over FTP post and created a simple but useful shell script to automate build and upload process.

I have recently switched to OpenBox, so today, I will use dynamic menus to integrate Firefox bookmarks with an existing OpenBox menu.

The end of the year is the best time to reinstall the operating system and change encryption keys due to a couple of additional free days at home so today I will shortly present my setup.

A couple of days on the road made me realize that I need a simple desktop utility that will download files when I sleep.

Several months ago, I have acquired wireless keyboard using tiny Logitech Unifying Receiver. Since that time I was a little worried by the lack of appropriate management options, however recently I found Solaar – a Linux device manager for such peripherals, which solves my doubts.

It is very easy to tell how long the system has been running using uptime command, but the information when exactly it was booted is not so apparent, so I will show you two different ways to get it.

Whenever I see an auto-login feature implemented by using an X login manager, I immediately think about how to automatically login a user at the console without even touching the graphical user interface.

It is good to know how to tell which package a specified file belongs to as this knowledge could be very useful during a system upgrade or unexpected system failure.

If you ever wondered how to determine whether the processor is 64-bit capable, then I have a simple and straight answer for you.

Recently I needed to set up software RAID1 during the Debian installation process. As it turned out, this process was simpler than I initially expected. I will shortly describe it here using screen-shots captured during initial tests.

Sometimes I need to explicitly indicate the execution of a specified shell script or just an action taken inside it. My favorite way is to use advanced pc-speaker beeper, which is directly available in Debian repository.

If you ever wondered about how to backup list of installed packages and then restore it on another machine then you need to know that it does not require anything more than three basic utilities – dpkg to import/export list of packages, apt-get to install selected packages and apt-mark to restore extended package states.

Generally I prefer to install Debian using a minimal CD so Apt-Cacher NG is an integral part of this process as I don’t like to wait during the installation process.

I am currently using a cellular connection most of the time. Thus, it is obvious that I prefer to reduce the amount of data transferred over the network. A significant portion of it is reduced by the apt caching proxy apt-cacher-ng as I use Debian Linux distribution and VirtualBox on a daily basis.

Simply dive into proc filesystem and read /proc/cmdline file to determine the kernel’s start-up parameters.

A couple of days ago, I was asked how to check the last mount time of the ext2/ext3/ext4 filesystem. The solution is straightforward as it does not require anything more than the tune2fs utility.

Static key configuration is the easiest and shortest way to set up an OpenVPN tunnel.

Today I will describe how to use rsync over ssh using four simple examples as it is a very convenient way to perform a secure and automated backup.

It is straightforward to display available updates using an application with a graphical user interface, but not so obvious to do it by using shell commands only. I will shed some useful light on the subject so we could both benefit from it.

I am using the Firefox web browser most of the time, but you need to know that I have drawn a clear line between daily browsing and strictly private usage by using a browser sandbox. I will shortly describe the whole process so you could also benefit from it.

I was always curious about how to list local displays as it is a quite interesting issue. Solution is not immediately apparent, but easy enough to spot after a while as it does not require anything more than little observations.

There are at least a couple of ways to hold a specific package and prevent it from being updated as you can use apt, dpkg, aptitude, dselect, or apt preferences, but only the last one is effective in every case.

I am playing with Linux Virtual Servers in the Linode Cloud for the last several days and a couple of times wanted to disable IPv6 for testing purposes.

Yesterday I experienced a strange problem after Kolab 3 installation on Debian Wheezy as I couldn’t add an initial user account using the admin interface.

After writing the previous blog entry, I started to think about how to specify page section when opening the manual page. It is a simple but quite interesting issue, so I quickly got curious and wrote this post to describe a straight solution. Just to be clear – I need to mention that I am not writing about section numbers describing distinct subject areas but just page sections, such as NAME, SYNOPSIS, DESCRIPTION, AUTHORS, and so on.

I was wondering how to read the total CPU usage of a group of processes. Then I came up with a straightforward solution using top and awk commands.

Today I will mention the arpwatch utility (developed by LBNL’s Network Research Group) as it is a small and very useful tool that will keep track of the Ethernet/IP address pairings and log every change which you can monitor and analyze.

I am constantly using SSH to transfer files between my home notebook and remote servers. The basic scp tool is great but sometimes it is more convenient to mount a remote file system to easily access files over the SSH protocol.

Today I was writing a shell script that performs different actions depending on the day of the month. Nothing fancy but then I came across an interesting issue, which is how to get number of days in a month. I got interested and started playing with shell commands, namely cal and awk utilities.

Re-read partition table without machine reboot using partprobe utility which is a part of parted package.

I was wondering how to easily install Steam on Debian Wheezy and unexpectedly found a solution on GitHub. To download and play Linux games available on Steam without any hassle you need to download and install Steam installer for Wheezy package.

A couple of days ago, I described a couple of interesting ways to interact with KDE using the D-Bus message bus. Today I will show how to set up a semi-intelligent screensaver to just wait during YouTube video playback.

Today I was playing with the D-Bus message bus and KDE so I will describe here a couple of basic actions that can be quickly automated by using shell commands. It shouldn’t matter much but I need to mention that I am using KDE 4.9.5.

Around three weeks ago I wrote an article on how to automate mouse and keyboard. It was a very fun experience but as the former article was quite long I didn’t mention the wmctrl tool. It is an excellent complement to the previously described tools.

A month ago I wrote an article – Debian – How to monitor battery capacity. Today I will publish long-term battery capacity graphs so you could see them for yourself.

I came across ACPI wakeup wiki article while writing previous post, got interested and checked how to automatically wake up notebook. It is really simple as you can quickly set wake up time using date command, just remember to use Unix time.

Recently I was wondering if it would be possible to automate mouse and keyboard actions. The answer is obviously yes as you can use xautomation and xdotool tools. I will describe them in a couple of simple examples.

Change the MAC address of an Ethernet interface and make this change permanent. I will briefly explain how to do this using standard commands and one particularly useful tool MAC Changer.

Recently I was wondering how to automatically set up an external monitor without using desktop utilities as I don’t like to configure it each time. This question provided me a lot of fun as it opens a couple of interesting possibilities.

Recently battery in my notebook started to behave erratically. It will charge only to 70-80% of its maximum capacity. I suspect that it is probably slowly dying, so I will have to replace it soon, but at first, I will look at several utilities to monitor battery capacity.

It is very annoying to hear loud beeps at home especially at night or when listening to music. To turn off the system bell just follow a couple of steps below and enjoy pure silence.

Yesterday, I wrote a short note about VLAN interfaces. Today, I want to write a short entry on how to bridge Ethernet interfaces to keep things complete as I need to mention creating an ACCESS port to tag packets on desired interface.

VLAN (virtual local area network) is a very useful concept as you can easily separate device management from users by using appropriate network devices and configuration. I will describe here in the form of a short note how to create a VLAN interface using a Debian system.

If you are searching for a book about Debian then look at The Debian Administrator’s Handbook. It is a great open source project so feel free to check it out and support it at the official The Debian Administrator’s Handbook website.

PCI-1610 is an Advantech 4-port RS-232 Universal PCI Communication Card which comes very handy if you need to connect more devices using serial port.

I am playing with DHCP option 82 so I need to read DHCP packets. The easiest way to do this is to use dhcpdump by Edwin Groothuis because of very simple usage and friendly output.

This is a rarely performed task but an easy one. To change time zone you need to reconfigure tzdata package.

Recently I needed to replicate data between two Linux servers so I could mitigate potential hardware failure. To achieve this goal I used GlusterFS – an Open Source distributed file system. In this example I will use Debian Wheezy as I want to try more recent version of GlusterFS.

From time to time I play older games on my notebook. I download them from Good Old Games and play on Linux as most of them work and it is easy to check which ones are supported using WineHQ website. Recently I installed PlayOnLinux and I like it because it allows you to keep and manage all Windows applications in one place.

Just a moment ago I connected my old hard drive and realized that it was a RAID member.

The fastest way to download or upload directory tree over FTP using just plain console is to execute lftp command.

To print current run-level execute: $ who -r run-level 3 2012-01-17 17:06 To print previous and current run-level execute: $ sudo runlevel N 3

Display established TCP connections inside the terminal.

Certificate could not be verified error.