• Run a process detached to the current terminal and monitor its output:

    $ nohup my_command &
    $ tail -F ./nohup.out
  • Same as above but with multiple commands, the last cloning a disk to another:

    $ nohup zsh -c "my_command && cat /dev/da1 > /dev/da0" &
    $ tail -F ./nohup.out
  • Run a process with a shell for a system user which has none (i.e. its default shell is set to /bin/false in /etc/passwd):

    $ su sys_user -s /bin/bash -c "my_command"


  • Get the exit code of the latest ran command:

    $ echo $?
  • Run the last command as root (source):

    $ sudo !!
  • Show the user under which I’m currently logged in:

    $ whoami
  • List of most used commands:

    $ history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort -rn | head
  • List cron jobs of the current user:

    $ crontab -l
  • If you have the following error:

    $ -bash: ./ /bin/bash^M: bad interpreter: No such file or directory

    Then the fix consist of removing the bad characters:

    $ sed -i 's/\r//' ./
  • Extract strings from a binary file:

    $ strings ./firmware.bin | less


  • Free up some memory by clearing RAM caches (source):

    $ sync ; echo 3 > /proc/sys/vm/drop_caches


  • Display which distro is running the system (source):

    $ lsb_release -a


    $ cat /etc/lsb-release


  • Disable a service on Debian/Ubuntu, then re-enable it:

    $ update-rc.d my-service-name remove
    $ update-rc.d my-service-name defaults
  • Same thing as above but on a RedHat-like system:

    $ chkconfig sshd --del
    $ chkconfig sshd --add


  • Speed-up Grub boot, but always show the boot menu:

    $ sudo sed -i 's/GRUB_TIMEOUT=10/GRUB_TIMEOUT=1/g' /etc/default/grub
    $ sudo sed -i 's/GRUB_HIDDEN_TIMEOUT/#GRUB_HIDDEN_TIMEOUT/g' /etc/default/grub
    $ sudo update-grub


  • List fonts available on the system:

    $ fc-list | cut -d ':' -f 2 | sort | uniq

Other Resources