Cheatsheet

Set Static IP

With Old version Ubuntu

sudo nano /etc/netplan/01-netcfg.yaml

edit content:
#######################################
network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      dhcp4: no
      addresses:
        - 192.168.121.221/24
      gateway4: 192.168.121.1
      nameservers:
          addresses: [8.8.8.8, 1.1.1.1]

New version (>=22.04)

sudo apt install openvswitch-switch

network:
  version: 2
  renderer: networkd
  ethernets:
    eth0:
      dhcp4: no
      addresses:
        - 192.168.0.10/24
      routes:
        - to: 0.0.0.0/0
          via: 192.168.0.1
      nameservers:
          addresses: [8.8.8.8, 1.1.1.1]

Troubleshoot DNS

sudo nano /etc/resolv.conf

Check what port running attach with what service

netstat -lntup
sudo lsof -i -P -n

Check driver Linux

lspci -v

Set timezone Vietnam

timedatectl set-timezone Asia/Ho_Chi Minh

Generate Random Password

openssl rand -base64 10

User Manager

Add User

useradd name_user
adduser name_user #detail about user

Switch User

su username

Delete

deluser username

Group Manager

groupadd
delgroup
usermod -aG group_name username #Append List all Group
#If not flag G, username will be delete on other group

Check which group user belong to

group username

Delete user from group

deluser username group

Privileges

tan@ubuntu:~/mkdocs/tanodd.github.io$ ls -l
total 16
drwxrwxrwx 4 root root 4096 Jan  3 06:37 docs
-rwxrwxrwx 1 root root  971 Jan  3 06:38 mkdocs.yml
drwxrwxrwx 4 root root 4096 Jan  3 04:35 site
drwxrwxrwx 4 root root 4096 Dec 31 07:28 venv

First Root is owner, Second Root is group owner

Change owner

chown root:tan docs/
        |   |
      user group

cat, less, head, tail