sudo

On a server you work as a normal user: sudo runs one command as root. Who may use it, sudo -u, and the > trap.

>_ Try it: a simulated Linux, right herenothing runs on your computer

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Examples

sudo -l what am I allowed to do?
sudo touch /srv/site/index.html create a file in a folder that belongs to root
ls -l /srv/site the file belongs to root
echo "hello" | sudo tee /srv/site/index.html write into it as root
sudo useradd -m -s /bin/bash intern create a user (root only)
sudo -u intern whoami run a command as that user

How it works

On real servers you log in as a normal user (the prompt ends in $). Files outside your home folder belong to root, so changing them says "Permission denied". sudo COMMAND runs that one command as root.

Only users in the sudo group (or listed in /etc/sudoers.d) may use it — id shows your groups. sudo -u USER runs a command as someone else instead.

Syntax

sudo [-u USER] COMMAND  |  sudo -l

Options

Option	What it does
`COMMAND`	run it as root
`-u USER`	run it as that user instead
`-l`	what you are allowed to run
`\| sudo tee FILE`	write a root-owned file (the > alone can't)

Good to know

sudo echo hi > /etc/motd still fails: the > is done by your own shell, before sudo runs. Use echo hi | sudo tee /etc/motd.
Avoid sudo -i (a whole root shell) for everyday work: one command at a time is safer and easier to read back.