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 and anacron.
• How-to: Add the following line to /etc/cron.daily/cache.
  • find ~/.cache/* -mtime +7 -exec rmtrash -rf {} \;
  • This will move files older than 7 days in ~/.cache to the trash every day.
• 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 and anacron.
• How-to: Add the following line to /etc/cron.daily/orph.
  • pacman -Qtdq | pacman -Rns -
• Additionally:

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.

11. Extract text containing keywords from any file.

• Description: This command will filter and sort text based on keyword from any file(s).
• Requires: GNU Coreutils, GNU grep
• How-to:
  • $ cat ./*/files* | grep -e keyword1 -e keyword2 | sort -u | nl > file
  • cat will take any file(s), multiple files in multiple subdirectories can be specified.
  • grep -e will look for any and/or all specified keywords.
  • sort -u will sort the results alphabetically and remove duplicates.
  • nl will add a number in front of every result (optionally).
  • > will write everything in a specified file.
• Additionally: This is simply an example of how useful the coreutils can be, especially when used together.

12. Enable parallel downloads for pacman.

• Description: Enable parallel downloads for faster updates with pacman.
• Requires: A pacman-based distro.
• How-to: Edit pacman's config-file at /etc/pacman.conf and uncomment ParallelDownloads and add a number of parallel downloads like 5 or 10.
  • # nano /etc/pacman.conf
• Additionally: ArchWiki: Pacman.

13. Enable smartd service.

• Description: Enable the smartd daemon to monitor SMART status and emit notifications to log.
• Requires: smartmontools
• How-to:
  • Enable the service # systemctl enable smartd.service
  • Uncomment/add the following line to /etc/smartd.conf: DEVICESCAN -a
• Additionally: ArchWiki: S.M.A.R.T.