Useful Linux Command Line Stuff

Most of the Information below is from the 2020 Canonical Ubuntu Server Pro Tips guide (no longer available)

In development: This page is very much in development and needa much work - send any suggestions to us via the normal channels! Note that some shells and distributions may vary in their syntax and so some commands may not work or be available (by default). Always read the relevant documentation for your distro before working on a live machine.

Commands to Manipulate Files

List files

ls

List files with permissions and dates

ls -al

create empty

touch <filename>

create with content

echo "<content>" > <filename>

append content

echo "<content>" >> <filename>

display a text file

cat <file>

copy

cp <file> <target filename>

move/rename

mv <file> <target directory/filename>

delete

rm <file>

Create a directory

mkdir <directory>

Create directories recursively

mkdir -p <directory1>/<directory2>

Delete a directory recursively

rm -r <directory>

Quick file search

locate

Search string in file

grep <string> <filename>

Search string recursively in directory

grep -Iris <string> <directory>

Find files modified in the last n minutes

find <directory> -mmin -<n> -type f

eg. find . -mmin -5 -type f

Show only the nth column

col<n> “<separator>” <filename>

eg. col2 “,” foo.csv

Display file paginated

less <filename>

Display first n lines

head -n <n> <filename>

Display last n lines

tail -n <n> <filename>

Follow file content as it increases

tail -f <filename>

Pack a directory into an archive

zip - zip -r <target> <source dir>

tar.gz - tar cvzf <target>.tar.gz <source dir>

Unpack an archive

zip - unzip <zip file>

tar.gz - tar xf <tar.gz file>

Copy file to remote server

scp <filename> <user@server>====<destination>

eg. scp config.yaml admin@192.0.0.0====/config

Copy directory recursively from remote server

scp -r <user@server>====<source> <destination>

eg. scp -r admin@192.0.0.0====/config /tmp

Networking

Get the IP address of all interfaces

networkctl status

Display all IP addresses of the host

hostname -I

Enable/disable interface

ip link set <interface> up

ip link set <interface> down

Manage firewall rules

enable firewall: sudo ufw enable

list rules: sudo ufw status

allow port: sudo ufw allow <port>

deny port: sudo ufw deny <port>

Connect remotely through SSH

ssh <user>@<host IP>

Packages

Search for packages

apt search <string>

snap find <string>

List available updates

apt list --upgradable

Apply all available updates

sudo apt update && sudo apt upgrade

Install from the Ubuntu archive:

sudo apt install <package>

Install from the snap store:

sudo snap install <package>

Which package provides this file?

sudo apt install apt-file

sudo apt-file update

apt-file <filename or command>

Security

Show which users are logged in

w

Get password expiration date for <user>

chage -l <user>

Set password expiration date for <user>

sudo chage <user>

Lock a user account

sudo passwd -l <user>

Unlock a user account

sudo passwd -u <user>

List open ports and associated processes

sudo netstat -tulpn

Automatically detect and ban abusive IP addresses

sudo apt install fail2ban

Show banned IP addresses

sudo fail2ban-client status

sudo fail2ban-client status <jail>

Get the support status for installed packages

ubuntu-support-status

Enable kernel live patching:

sudo snap install canonical-livepatch

sudo canonical-livepatch enable <token>

Visit ubuntu.com/livepatch to get a free token for up to 3 machines.

System

Display kernel version

uname -r

Get disk usage

df -h

Get memory usage

cat /proc/meminfo

Get system time

timedatectl status

Set system timezone

timedatectl list-timezones

sudo timedatectl set-timezone <zone>

Get all running services

systemctl --state running

Start or stop a service

service <service> start/stop

Monitor new logs for a service

journalctl -u <service> --since now -f

Kubernetes and containers

Install MicroK8s and list available add-ons

sudo snap install microk8s --classic

microk8s.status --wait-ready

Enable a MicroK8s add-on

microk8s.enable <service>

View MicroK8s nodes and running services

microk8s.kubectl get nodes

microk8s.kubectl get services

Launch a LXD container

lxd init

lxc launch ubuntu:18.04 <container name>

Or another distro

lxc launch images:centos/8/amd64 <container name>

Get a shell inside a LXD container

lxc exec <name> -- /bin/bash

Push a file to a LXD container

lxc file push <filename> <container name>/<path>

Pull a file from a LXD container

lxc file pull <destination> <container name>/<file path>

Virtualisation

Install Multipass and launch an Ubuntu VM

sudo snap install multipass --classic

multipass launch <image> --name <VM name>

Omitting <image> will launch a VM withthe latest Ubuntu LTS

Find available images

multipass find

List existing VMs

multipass list

Get a shell inside a VM

multipass shell <VM name>

OpenStack

Install OpenStack and launch an instance

sudo snap install microstack --classic

sudo microstack.init

microstack.launch

The Horizon dashboard is available at 10.20.20.1

Default credentials: admin / keystone