Linux Tech Tips

This is a random collection of useful things I came across.
It's mostly distro-agnostic but sometimes specific for pacman-based distros.

TOC

0. Short example template.

• Description: What is this good for.
• Requires: Do you need any particular software (provide a link)?
• How-to: Straight forward description and maybe a code example.
  • Detailled description if necessary.
  • # this is the actual code lol
• Aditionally: Anything else that might be important like additional ressources.

1. Automatic clear cache.

• Description: Automatically move files older than a specific amount of time from your user's ~/.cache directory to the trash.
• Requires: The rmtrash package.
• How-to: Add the following line to your crontab using the command "crontab -e" (or EDITOR=$editor crontab -e).
  • 0 17 * * * /usr/bin/find ~/.cache/* -mtime +7 -exec /usr/bin/rmtrash -rf {} \;
  • This command looks at files in ~/.cache every day at 5 p.m. and moves files older than 7 days to the trash.
• Additionally: This can also be done using regular rm instead of rmtrash.

2. Limit systemd journal size.

• Description: Limit the systemd journal to a specific size.
• Requires: Specific to systems using systemd.
• How-to: Edit /etc/systemd/journald.conf and change SystemMaxUse=50M.
• Additionally: ArchWiki: systemd.
• Additionally: This can also be achieved using journalctl and be limited by time.

3. Syntax highlight for nano.

• Description: Enable syntax highlighting for nano.
• Requires: The nano editor.
• How-to: Edit ~/.config/nano/nanorc or to /etc/nanorc and add the following:
  • include "/usr/share/nano/*.nanorc".
• Additionally: ArchWiki: Nano.

4. Repeat a command using watch.

• Description: Repeat and watch a command in a custom interval.
• Requires: The procfs package.
• How-to: Use watch followed by your command.
  • Example: # watch -n 1.0 "du -h -s ./$folder
  • This prints the summarized size of $folder in human-readable format every second.
• Additionally: ---

5. Repeat last command as su.

• Description: Repeat the last command using sudo.
• Requires: The sudo package.
• How-to: Just type sudo !! and the last command will be repeated using sudo.
• Additionally: ---

6. Prevent overwriting files.

• Description: Use alias for rm, cp and mv.
• How-to: Add the following alias into your ~/.bashrc.
  • Use -interactive option to get asked before overwriting files.
  • alias mv="mv -i"
• Additionally: ArchWiki: Core utilities.

7. Auto-clean package cache.

• Description: Automatically clean the pacman package cache using paccache.
• Requires: A pacman-based distro and the pacman-contrib package.
• How-to: Enable the paccache.timer.
  • # systemctl enable paccache.time
• Additionally: Edit the paccache.service in /usr/lib/systemd/system/ and change the command to e.g. keep the latest installed version and no uninstalled version of all packages: ExecStart=/usr/bin/paccache -rk1 && /usr/bin/paccache -ruk0

8. Passwordless SSH.

• Description: Connect to a remote maschine using SSH without a password.
• Requires: A SSH implementation like TinySSH.
• How-to: Generate a keypair and send the public key to the remote maschine's authorized keys.
  • Generate a keypair: ssh-keygen -t rsa
  • Send the key: ssh-copy-id $remote-username@$remote-ip-address
  • Fill in the username and IP address of your remote maschine.
  • For example: ssh-copy-id foo@192.168.178.123
• Additionally: Here's a more detailed tutorial.

9. Automatic clean orphaned packages.

• Description: Automatically remove orphaned packages.
• Requires: A pacman-based distribution.
• How-to: Add the following line to your crontab.
  • 0 20 * * * /usr/bin/pacman -Qtdq | /usr/bin/pacman -Rns -
• Additionally: This example removes orphans everyday at 8 p. m. but the

10. Automatic retrieve latest mirrors.

• Description: Automatically retrieve the latest Arch Linux mirrors and write them to the mirrorlist.
• Requires: An Arch-based distro and reflector.
• How-to: Install reflector and enable the reflector.timer.
  • # systemctl enable reflector.timer
• Additionally: ArchWiki: Reflector.