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Useful Commands

This document gathers commands that I found useful in work, which might not be used very often. They might not be easy to remember, so I decide to put them together here.

Device information​

Get device IP with ifconfig or ip​

# 192 is used to search the ip. Change it as needed.
if config | grep 192 
ip a | grep 192

Get device OS with lsb_release​

lsb_release -a

File operations​

Download a file with wget​

wget file-link

Transfer file(s) between host and server with scp​

# copy a single file
scp host-file-path server-username@ip-address:server-directory

# copy a folder
scp -r host-folder server-username@ip-address:server-directory

Unzip files with unzip, unxz, and tar​

unzip package.zip
unxz package.xz
tar -xvf package.tar

Manage permissions with chmod​

# make a file have rwxrwxrwx permissions
chmod 777 file-path

# make every single file under / have rwxrwxrwx permissions
chmod -R 777 /

# shows current file permissions
ls -lt

Manage users​

# add a new user
adduser newuser

# query which group a user is is
groups newuser
# by default, a user and its own group share the same name

# add a new user to the sudo group
usermod -aG sudo newuser
sudo usermod -aG sudo newuser

# delete a new user
deluser newuser

See How to Add and Delete Users on Ubuntu 20.04 for more information.