Tag: bash commands

Ubuntu Server CLI Cheatsheet

The world’s most popular server OS – CLI essentials for daily administration
Ubuntu Server 25.10 (Questing Quokka) released October 2025: Kernel 6.17, OpenJDK 25, Python 3.14 RC3, Golang 1.25, Rust 1.85. LTS: 24.04 (Noble Numbat) with 12 years support via Ubuntu Pro.
Debian-based with apt package manager. All privileged commands require sudo. Access via SSH (port 22) or console.

1. Installation & Initial Setup

Task	Command / Action
Download ISO	ubuntu.com/download/server → 25.10 (latest) or 24.04 LTS
Boot & Install	USB boot → Language → Install Ubuntu Server → Set hostname, user, SSH key (recommended)
Enable SSH	During install: Check Install OpenSSH server Post-install: sudo apt install openssh-server
Update system	sudo apt update && sudo apt upgrade -y
Set timezone	sudo timedatectl set-timezone America/New_York (or your region)
Configure firewall (UFW)	sudo ufw allow OpenSSH sudo ufw enable
Add user to sudo	sudo usermod -aG sudo username

Cloud Images: For AWS/GCP/Azure: Use official AMIs. Minimal install: ~300MB RAM. Pro Tip: Enable unattended upgrades: sudo apt install unattended-upgrades → sudo dpkg-reconfigure unattended-upgrades.

2. Navigation & File Management

Task	Command
Show current directory	pwd
List files (detailed)	ls -la
List by time (newest first)	ls -lht
List with human-readable sizes	ls -lh
Change directory	cd /var/www
Go home	cd ~
Go up one level	cd ..
Go to previous directory	cd –
Show directory tree	tree -L 2 (install: sudo apt install tree)

3. Create, Copy, Move & Delete

Action	Command
Create directory	mkdir foldername
Create nested directories	mkdir -p /path/to/nested/folder
Create empty file	touch filename.txt
Create multiple files	touch file1.txt file2.txt file3.txt
Edit/create with nano	nano filename.txt (Ctrl+O save, Ctrl+X exit)
Copy file	cp file.txt /backup/
Copy directory recursively	cp -r folder /backup/
Move/rename file	mv old.txt new.txt
Move file	mv file.txt /new/location/
Delete file	rm file.txt
Delete directory	rm -r folder (empty) rm -rf folder (with contents, dangerous!) rm -ri folder (with prompts)

4. Disk & Storage

Task	Command
Disk usage (human-readable)	df -h
Detailed disk output	df -h –output=source,fstype,size,used,avail,pcentused,target
Folder size	du -sh /path
Current directory sizes (largest first)	du -sh * \| sort -hr
List block devices	lsblk
List all disks	sudo fdisk -l
Interactive disk explorer	ncdu / (install: sudo apt install ncdu)

5. Search & Find

Task	Command
Find files by name	find /var/www -name “*.log”
Find large files (>100MB)	find / -type f -size +100M 2>/dev/null
Search text in files	grep -r “search term” /var/www
Case-insensitive filenames only	grep -ril “text” /etc

6. Permissions & Ownership

Action	Command
Set file permissions (644)	chmod 644 file.txt
Make executable (755)	chmod 755 script.sh
Recursive permissions	chmod -R 755 folder
Change owner	chown www-data:www-data file.txt
Recursive ownership	chown -R www-data:www-data /var/www
Take ownership	chown -R $USER:$USER folder

7. System Monitoring & Info

Task	Command
Kernel & system info	uname -a
Ubuntu version	lsb_release -a
Uptime & load	uptime
Memory usage	free -h
Process monitor	top or htop (install: sudo apt install htop)
Recent logs	journalctl -xe
Kernel messages	dmesg \| tail

8. Package Management (APT)

Action	Command
Update package list	sudo apt update
Upgrade packages	sudo apt upgrade -y
Full upgrade (with deps)	sudo apt full-upgrade -y
Remove unused	sudo apt autoremove
Clean cache	sudo apt clean
Install tools	sudo apt install tree htop ncdu
Search package	apt search keyword
Show package info	apt show package

9. Networking & Users

Networking

Task	Command
Show IP addresses	ip a
Listening ports	ss -tulnp
Public IP	curl ifconfig.me
Test connectivity	ping -c 4 google.com
Firewall status	sudo ufw status
Allow SSH	sudo ufw allow 22/tcp

Users

Action	Command
Add user	sudo adduser username
Add to sudo group	sudo usermod -aG sudo username
Change password	sudo passwd username
Edit sudoers	sudo visudo

10. Troubleshooting

Issue	Command
Fix broken packages	sudo apt install -f
Check services	sudo systemctl status service
View full logs	journalctl -u service -f
Boot to recovery	GRUB → Advanced → Recovery Mode
Clear old logs	sudo journalctl –vacuum-time=30d
Reinstall package	sudo apt install –reinstall package

11. One-Liners

# Full update + clean

sudo apt update && sudo apt full-upgrade -y && sudo apt autoremove && sudo apt clean

# Clean disk view (hide snaps)

df -h | grep -v snap

# 10 largest items in current dir

du -sh * | sort -hr | head -10

# Delete logs older than 30 days

find /var/log -type f -mtime +30 -delete

# Newest files in /var/log

ls -lht /var/log | head

# Quick web server (Python)

cd /var/www && python3 -m http.server 8000

12. Useful Tools to Install

sudo apt install htop tree ncdu curl wget vim git ufw unattended-upgrades

13. Ubuntu Resources

Official Docs: https://ubuntu.com/server/docs
Ask Ubuntu: https://askubuntu.com
Cloud/Server Guide: https://ubuntu.com/server

# Check for updates offline

apt list –upgradable

November 23, 2025

Arch Linux Cheatsheet

Essential commands for installation, package management, system administration, and troubleshooting
Assumes pacman as primary package manager. All commands require sudo unless run as root.

1. Installation (Live USB/ISO)

Task	Command
Update keyring (critical first step)	`pacman -Sy archlinux-keyring --noconfirm`
Sync mirrors (fastest)	`reflector --latest 10 --sort rate --save /etc/pacman.d/mirrorlist`
List disks	`lsblk -f` or `fdisk -l`
Partition disk (example: UEFI + root)	`cfdisk /dev/sdX`
Format partitions	`mkfs.fat -F32 /dev/sdX1` (EFI) `mkfs.ext4 /dev/sdX2` (root)
Mount partitions	`mount /dev/sdX2 /mnt` `mkdir -p /mnt/boot && mount /dev/sdX1 /mnt/boot`
Install base system	`pacstrap /mnt base linux linux-firmware`
Generate fstab	`genfstab -U /mnt >> /mnt/etc/fstab`
Chroot into system	`arch-chroot /mnt`
Set timezone	`ln -sf /usr/share/zoneinfo/Region/City /etc/localtime` `hwclock --systohc`
Set locale	Edit `/etc/locale.gen` → uncomment `en_US.UTF-8 UTF-8` `locale-gen` `echo "LANG=en_US.UTF-8" > /etc/locale.conf`
Set hostname	`echo "myhostname" > /etc/hostname`
Add to `/etc/hosts`	`127.0.0.1 localhost` `::1 localhost` `127.0.1.1 myhostname.localdomain myhostname`
Set root password	`passwd`
Install bootloader (GRUB UEFI)	`pacman -S grub efibootmgr` `grub-install --target=x86_64-efi --efi-directory=/boot --bootloader-id=GRUB` `grub-mkconfig -o /boot/grub/grub.cfg`
Enable network (systemd)	`pacman -S networkmanager` `systemctl enable NetworkManager`
Exit & reboot	`exit` `umount -R /mnt` `reboot`

2. Pacman (Package Management)

Action	Command
Update system	`pacman -Syu`
Install package	`pacman -S package`
Remove package (with deps)	`pacman -Rns package`
Search package	`pacman -Ss keyword`
List installed packages	`pacman -Q`
List explicitly installed	`pacman -Qe`
Clean cache (keep last 3 versions)	`paccache -rk 3`
Remove untracked packages	`pacman -Rns $(pacman -Qdtq)`
View package info	`pacman -Qi package`
List files in package	`pacman -Ql package`
Which package owns file	`pacman -Qo /path/to/file`
Sync database	`pacman -Syy`
Force refresh	`pacman -Syyu`

AUR Helper (yay/paru)
Install: pacman -S --needed git base-devel
git clone https://aur.archlinux.org/yay.git && cd yay && makepkg -si
Use: yay -S package (replaces pacman for AUR)

3. System Administration

Task	Command
List services	`systemctl list-unit-files --type=service`
Enable service	`systemctl enable service`
Start service	`systemctl start service`
Check status	`systemctl status service`
View logs	`journalctl -u service`
Reboot	`reboot`
Shutdown	`poweroff`
View kernel messages	`dmesg \| less`
Check disk usage	`df -h`
Check memory	`free -h`
List processes	`htop` or `top`
Kill process	`kill PID` or `pkill name`
Edit config (nano/vim)	`nano /path/to/file`
Backup pacman database	`cp -r /var/lib/pacman /backup/`

4. Users & Permissions

Action	Command
Add user	`useradd -m -G wheel username`
Set user password	`passwd username`
Enable sudo for wheel	`EDITOR=nano visudo` → uncomment `%wheel ALL=(ALL) ALL`
Change file owner	`chown user:group file`
Change permissions	`chmod 755 file`

5. Networking

Task	Command
Check IP	`ip a`
Test connection	`ping archlinux.org`
Wi-Fi (iwctl)	`iwctl` → `station wlan0 scan` → `connect SSID`
Enable Wi-Fi	`systemctl enable --now iwd`
Check DNS	`cat /etc/resolv.conf`
Restart NetworkManager	`systemctl restart NetworkManager`

6. Filesystem & Storage

Task	Command
Mount USB	`mount /dev/sdb1 /mnt/usb`
Unmount	`umount /mnt/usb`
Format ext4	`mkfs.ext4 /dev/sdX1`
Check filesystem	`fsck /dev/sdX1`
Find large files	`du -ah / \| sort -rh \| head -n 20`
Search files	`find / -name "filename"`

7. Troubleshooting

Issue	Command
Boot into recovery	Hold `Shift` at boot → GRUB → `e` → add `systemd.unit=rescue.target`
Fix broken packages	`pacman -Dk` (check deps) `pacman -Syu --overwrite '*'`
Reinstall all packages	`pacman -Qnq \| pacman -S -`
Clear journal logs	`journalctl --vacuum-time=2weeks`
Check boot errors	`journalctl -b -p err`
Regenerate initramfs	`mkinitcpio -P`
Update GRUB	`grub-mkconfig -o /boot/grub/grub.cfg`

8. Useful Tools to Install

pacman -S vim htop git curl wget unzip tree reflector rsync

9. One-Liners

# Full system update + clean
pacman -Syu && paccache -ruk0 && pacman -Rns $(pacman -Qdtq)

# Mirrorlist (fastest 10 servers)
reflector --latest 10 --sort rate --save /etc/pacman.d/mirrorlist && pacman -Syy

# Show orphan packages
pacman -Qdt

# Rebuild AUR packages after upgrade
yay -Syu --rebuildall

10. Arch Wiki Shortcut

Always check: https://wiki.archlinux.org

# Search wiki offline (install arch-wiki-docs)
pacman -S arch-wiki-docs
wiki-search "query"

Pro Tip: Keep archinstall script for automated installs:

pacman -S archinstall
archinstall

October 31, 2025