Useful Linux Command Line Stuff

From the Ubuntu Server Pro Tips guide:

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>

Files

List files

ls

List files with permissions and dates

ls -al

Common file operations

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

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

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 More MicroK8s help at microk8s.io/docs 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> More LXD help at linuxcontainers.org/lxd

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 with the latest Ubuntu LTS Find available images multipass find

List existing VMs multipass list Get a shell inside a VM multipass shell <VM name> More Multipass help at discourse.ubuntu.com

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 More MicroStack help at microstack.run/docs