Linux / Bash Cheatsheet

Note: A lot of these commands are unique and special to Debian or Ubuntu distributions. There are typically alternate forms of these expressions for other distributions.

Find Kernel version

uname -r

More detailed information

uname -a

Find release name

lsb_release -a

List all kernel images installed:

dpkg --list | grep linux-image

Crontab

how to run python scripts: https://www.geeksforgeeks.org/how-to-schedule-python-scripts-as-cron-jobs-with-crontab/

create a new python script

#!/usr/bin/env python3
import time
import os
with open(os.path.expanduser('~/crontest.txt'),'a') as f:
    f.write(time.ctime()+'\n')

chmod +x test.py

crontab -e

# m h  dom mon dow   command
* * * * * $HOME/test.py

GUI

ctrl-h hides and shows "dot" files in nautilus like .config or .ssh/

Login, Logout, Restart

sudo reboot now
sudo shutdown now
gnome-session-quit

Ubuntu Specific

From https://fostips.com/lid-close-action-ubuntu-21-04-laptop/

edit /etc/systemd/logind.conf to configure power options such as lid closing opening,

HandleLidSwitch=ignore
HandleLidSwitchExternalPower=ignore
HandleLidSwitchDocked=ignore

1. Restart Service

systemctl restart systemd-logind.service

Backup folders

/bin /boot /etc /home /lib /lib64 /opt /root /sbin /usr /var

https://askubuntu.com/questions/222326/which-folders-to-include-in-backup

How to find .desktop file location for a particular application

For example, if "Image Viewer" is in the name of the icon:

find / -name '*.desktop' -exec grep -H 'Image Viewer' {} \; 2>/dev/null

derived from here: https://askubuntu.com/questions/1160737/how-to-find-desktop-file-location-for-a-particular-application:

Some default locations listed here: https://askubuntu.com/questions/1146307/which-desktop-files-belong-where:

/usr/share/applications/gnome-terminal.desktop
~/.local/share/applications/gnome-terminal.desktop
~/.config/gnome-panel/launchers/gnome-terminal.desktop
~/.gnome/apps/gnome-terminal.desktop

Trash

Files can be stuck in ~/.local/share/Trash/expunged when you delete from Nautilus a folder that belongs to you, but contains files which are belong to another user, and it is tricky for Nautilus to handle this situation correctly. To delete them try to use:

sudo -i
rm -rv /home/<desired_user_name>/.local/share/Trash/expunged/*
exit

More

see this page for more links

Accidentally deleted sudoers

use pkexec to do things you would normally do with sudo, like

pkexec cp /path/to/sudo/backup /etc/sudoers

great advice from here: https://askubuntu.com/questions/438123/accidentally-deleted-etc-sudoers-file

close bash without saving history

unset HISTFILE && exit

or

history -c && history -w && exit

Systemctl

To find services

sudo systemctl list-units --type=service

To reload the service daemon

sudo systemctl daemon-reload

other common functions:

sudo systemctl edit <servicename>
sudo systemctl enable <servicename>
sudo systemctl start <servicename>
sudo systemctl status <servicename>
sudo systemctl stop <servicename>
sudo systemctl disable <servicename>
sudo systemctl reload <servicename>
sudo systemctl restart <servicename>