Linux (Ubuntu) Cheatsheet

This article is a bit old and the content may be outdated, so please refer to it with caution and remember to check the latest official materials (such as documentation, etc.)

Useful commands and tips about system operation. Things more about scripting are in Bash Cheatsheet

`systemctl`

Where are service files? #

/etc/systemd/system/service-name.service

text

Start at Boot #

sudo systemctl enable sshd.service

bash

disable is the opposite.

Use Environment in Service Unit File #

[Service]
Environment=PATH=/home/pi/.local/bin:/home/pi/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

ini

Note
$PATH do not have its special meaning here.
https://askubuntu.com/questions/1014480/how-do-i-add-bin-to-path-for-a-systemd-service for advanced.

Unit File Template #

Click to expand

[Unit]
Description=Jupyter Notebook

[Service]
Type=simple
PIDFile=/run/jupyter.pid
Environment=PATH=/home/pi/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
ExecStart=jupyter lab --config=/home/pi/.jupyter/jupyter_notebook_config.py
User=pi
Group=pi
WorkingDirectory=/home/pi/Notebooks/
Restart=always
RestartSec=10
#KillMode=mixed

[Install]
WantedBy=multi-user.target

ini

Exited Without Error Log? #

From https://unix.stackexchange.com/questions/225401/how-to-see-full-log-from-systemctl-status-service/225407

Use journalctl command. e.g.

journalctl -u service-name.service

bash

-u is short for --unit. More useful options:

-f, --follow: Show only the most recent journal entries, and continuously print new entries as they are appended to the journal.
-r, --reverse: Reverse output so that the newest entries are displayed first.

`apt`

List All Versions #

https://askubuntu.com/questions/473886/list-all-versions-of-a-package

apt-cache madison chromium-browser
# or
apt-cache showpkg lyx

bash

Install Specific Version #

https://askubuntu.com/questions/428772/how-to-install-specific-version-of-some-package

# get version of installed package
apt-cache policy <package name>
# install a specific package version
sudo apt-get install <package name>=<version>

bash

OS Release Info #

cat /etc/os-release

bash

List All Users #

less /etc/passwd

bash

`lsof`

LiSt Open Files. A very powerful tool.

For network checking:

ls -i [46][protocol][@hostname|hostaddr][:service|port]

text

e.g.

sudo lsof -i :80

shell

`find`

find -iname 'qwerty'
find dir/ -iname 'qwerty'
find -name 'Qwerty'

bash

No Wireless Connection After Sleep #

sudo service network-manager restart

bash