Linux Cheat Sheet | Ziye's Blog

Links

“The art of command line” should have included most essential commmands. https://github.com/jlevy/the-art-of-command-line

“Linux Productivity Tools” by Ketan M. https://www.olcf.ornl.gov/wp-content/uploads/2019/12/LPT_OLCF.pdf

Plus all kinds of cheatsheets online. https://tmuxcheatsheet.com/

You would thank shellcheck.

My Tips

I don’t think there is any meaning memorising all the commands and options. I learn the commands when I use them. I forget if I don’t touch them for a long time.

On top of that, why would I bother when I have handy tools like tldr, cheat.sh and man.

The really important commands you should remember are:

brew install tlrc
tldr tar
# or
curl cht.sh/tar
# or
man tar

Commands

File

grep <pattern> <file>
zcat <file.gzip>
zless <file.gzip>
head/tail -n 10
tail -f <file>
scp <server:path> <dest>
du -sh <path> | sort -h
cat <file> | tr '\n' ';'
sed tldr
tee
find . -maxdepth 1 -type f -exec wc -l {} \;
cmd > log.txt 2>&1 redirect stderr and stdout to log.txt
split --number 2 <file> Used one time when I have to split a 10G file into under 1G per file.

I can spend a section on sed and awk and more on find. But I will probably ask AI when I want to use them.

File permisson:

# user group other
-rwxrwxrwx
# directory
drwxrwxrwx

SSH

ssh-keygen -t ed25519 -a 32 -f ~/.ssh/id_ed25519 -C "comment"

Bash

set -euo pipefail exit immediately if a command exits with non-zero status.
history
Heredoc
```
cat << EOF
line 1
line 2
EOF
```

System

top
ps aux
lsof -i :8080
lsof -p <PID> | wc -l check number of file descriptors.
lshw
df
free --human Show free memory
uname -a details about the current machine and the operating system
lsb_release -a
uptime
w Show who is logged on and what they are doing.
hostname
nohup <script.sh> &
jobs
kill <pid>
sudo nvme smart-log <device>. Checking the SSD status. Probably the last thing to confirm when a database was down.
systemctl status <service>

Network

host <domain> <dns>
ufw Uncomplicated Firewall
ip addr
dig example.com
netstat -tuln

DNS file: /etc/resolv.conf

Notes

An inode stores all metadata about a file, except for the filename.

Hard links:

Only link to a file, not a directory
Can’t reference a file on a different disk/volume
Links will reference a file even if it is moved
Links reference inode/physical locations on the disk

Symbolic (soft) links:

Can link to directories
Can reference a file/folder on a different hard disk/volume
Links remain if the original file is deleted
Links will NOT reference the file anymore if it is moved
Links reference abstract filenames/directories and NOT physical locations.
They have their own inode