Linux

Gnome #

• For restarting the shell, try in this order (1):
  • Alt + F2 -> r
  • pkill -HUP gnome-shell in another TTY (should not logout the user on X11)
  • systemctl restart gdm (will logout the user)

NFS mounts #

NFS mounts can be tricky. After an NFS request times out, NFS request are retried indefinitely by default. This can lead to unexpected hangs on the client. (1)
Use the mount option soft to limit the number of retries to 3.

If an NFS share hangs, it can be unmounted as follows: Find the mount point using mount and then umount -f -l [mount point] (-f for force and -l for lazy unmount, i.e. detach now and cleanup references later) (2)

Ubuntu #

• Night light not working correctly: Try killall gsd-color (1) and, if that doesn’t work, follow it by /usr/libexec/gsd-color

• Analog sound output not appearing: Try pactl load-module module-detect (2)

• Wired network connection not working anymore after sleep (shows up as “Cable unplugged” in Settings): I’ve had this happen every once in a while. The typical commands to restart various networking services (e.g. systemctl restart NetworkManager, ip link set enp7s0 down; ip link set enp7s0 up) don’t work for me in this case. So far, I’ve always solved this by restarting the computer, but it can actually also be fixed by just reloading the driver (2, 3):

  First find out the driver in use by running sudo lshw -C network. There will be a line that contains driver=<driver> (in my case igb).

  Then, unload and reload the driver:

  sudo modprobe -r <driver>
  sudo modprobe -i <driver>
  

  So, in my case:

  sudo modprobe -r igb
  sudo modprobe -i igb
  

Grep #

• Find files not containing a string: grep -L [string] [files] (e.g. grep -L foo *)

Disks #

• Remove filesystems on a disk: wipefs -a /dev/sd[x] (1)

Shells #

• Running a command [cmd] that is shadowed by an alias (1), try:
  • \[cmd]
  • command [cmd]
  • '[cmd]' or "[cmd]"

freedesktop.org #

• Update cache database of MIME types handled by desktop files: sudo update-desktop-database (1)

rsync #

• Typical rsync parameters: rsync -ah --info=progress2 [source] [dest], where:
  • -a: ‘archive’ (equal to -rlptgoD), where in turn:
    • -r: ‘recursive’
    • -l: copy symlinks as symlinks
    • -p: preserve permissions
    • -t: preserve modification times
    • -g: preserve group
    • -o: preserve owner (requires root)
    • -D: preserve device (requires root) and special files
  • -h: ‘human readable’
  • --info=progress2: display progress info for whole transfer instead of individual files (--progress)
• Additional sometimes useful parameters:
  • -v: print transferred files
  • --delete: delete extraneous files from destination
  • -u: skip files that are newer at destination
  • --dry-run: output changes without actually making them
  • --partial: keep partially transferred files in destination if transfer is aborted
  • -z: compress

LVM #

• To expand a logical volume (for example after cloning to a larger disk):
  • Resize the partition using gparted (if necessary).
  • Run lvresize -l +100%FREE /dev/mapper/[lv], e.g. lvresize -l +100%FREE /dev/mapper/ubuntu--vg-root.
  • Run resize2fs -p /dev/mapper/[lv].

Misc #

• For documenting command line arguments, refer to docopt.
• Encrypt files with 7zip (will prompt for password): 7z a -p -mhe -t7z [archive_name].7z [filenames...] (1)