Cheat Sheets

Three quick-reference tables tuned by role—most-used commands with the flags that matter. Click Copy sheet for plain text, or use your browser print dialog (Cmd/Ctrl+P) for a printable version.

dev sysadmin infra

Developer Cheat Sheet

Daily CLI: repos, logs, local processes, text munging, HTTP checks.

dev

Files & search

Command	Example	Use when
`ls`	`ls -la`	List all files with permissions
`cd`	`cd -`	Toggle previous directory
`pwd`	`pwd -P`	Resolve symlinks in path
`find`	`find . -name '*.ts'`	Locate files in tree
`grep`	`grep -rn "TODO" src/`	Search code recursively
`rg`	`rg -l pattern`	Faster ripgrep search (if installed)
`tree`	`tree -L 2 -I node_modules`	Visualize project layout

View & edit

Command	Example	Use when
`cat`	`cat .env.example`	Small file to stdout
`less`	`less +F app.log`	Follow log live
`tail`	`tail -n 200 -f log`	Last lines + follow
`head`	`head -n 5 file.csv`	Peek header rows
`wc`	`wc -l *.log`	Line counts

Text processing

Command	Example	Use when
`sed`	`sed -i.bak 's/old/new/g' f`	In-place replace
`awk`	`awk '{print $1}' log`	Column extraction
`sort`	`sort -u file.txt`	Unique sorted lines
`uniq`	`sort f \| uniq -c`	Count duplicates
`xargs`	`find . -name '*.tmp' -print0 \| xargs -0 rm`	Safe batch delete

Processes & sessions

Command	Example	Use when
`ps`	`ps aux \| grep node`	Find dev server PID
`kill`	`kill -TERM $PID`	Stop hung dev server
`lsof`	`lsof -i :3000`	Who owns port 3000
`tmux`	`tmux new -s dev`	Persistent terminal session
`jobs`	`fg %1`	Background job control

Network & archives

Command	Example	Use when
`curl`	`curl -fsS localhost:8080/health`	API health check
`ssh`	`ssh -L 5432:localhost:5432 db`	Local port forward to DB
`scp`	`scp build.zip user@host:/tmp/`	Copy artifact to server
`tar`	`tar -czvf out.tgz dir/`	Archive for deploy
`tar`	`tar -xzvf in.tgz`	Extract release

Shell shortcuts

Syntax	Example	Use when
`\|`	`cat log \| grep ERR`	Pipeline filter
`2>&1`	`cmd >out.log 2>&1`	Merge stderr to stdout
`$?`	`echo $?`	Last exit code
`export`	`export NODE_ENV=dev`	Env for child processes
`history`	`Ctrl+r`	Reverse search history

SysAdmin Cheat Sheet

Users, permissions, services, packages, logs, and scheduled jobs.

sysadmin

Users & access

Command	Example	Use when
`id`	`id deploy`	UID, groups for account
`useradd`	`useradd -m -s /bin/bash u`	Create login user
`usermod`	`usermod -aG sudo u`	Add to group
`passwd`	`passwd -l u`	Lock account
`sudo`	`sudo -l`	List allowed commands
`visudo`	`visudo`	Edit sudoers safely
`who`	`w`	Logged-in sessions

Permissions

Command	Example	Use when
`chmod`	`chmod 600 id_rsa`	SSH key permissions
`chmod`	`chmod -R g+w /var/shared`	Group-writable share
`chown`	`chown -R www-data:www-data /var/www`	Web root owner
`umask`	`umask 027`	Default new file modes
`getfacl`	`getfacl /data/share`	Inspect ACLs

Services (systemd)

Command	Example	Use when
`systemctl`	`systemctl status nginx`	Service state
`systemctl`	`systemctl restart nginx`	Apply config (after test)
`systemctl`	`systemctl reload nginx`	Graceful reload (SIGHUP)
`systemctl`	`systemctl enable --now u`	Start on boot
`journalctl`	`journalctl -u nginx -f`	Follow service logs
`journalctl`	`journalctl -p err -b`	Errors this boot

Packages

Command	Example	Use when
`apt`	`apt update && apt upgrade -y`	Debian/Ubuntu patch
`apt`	`apt install pkg`	Install package
`dnf`	`dnf install pkg`	RHEL/Fedora install
`rpm`	`rpm -qa \| grep pkg`	Query installed RPM
`dpkg`	`dpkg -l \| grep pkg`	Query installed deb

Disk & logs

Command	Example	Use when
`df`	`df -h`	Filesystem space
`df`	`df -i`	Inode exhaustion
`du`	`du -sh /var/log/*`	Log directory sizes
`tail`	`tail -f /var/log/syslog`	Classic syslog follow
`logrotate`	`logrotate -d /etc/logrotate.conf`	Debug rotation config

Scheduling

Command	Example	Use when
`crontab`	`crontab -e`	Edit user cron
`crontab`	`crontab -l`	List jobs
`at`	`echo cmd \| at 02:00`	One-shot schedule
`systemctl`	`systemctl list-timers`	systemd timers

Infra / DevOps Cheat Sheet

Networking, storage, performance, remote ops, and incident triage.

infra

Networking

Command	Example	Use when
`ss`	`ss -tlnp`	Listening TCP ports + PIDs
`ss`	`ss -tan state established`	Active connections
`ip`	`ip addr show`	Interfaces & IPs
`ip`	`ip route show`	Routing table
`ping`	`ping -c 4 host`	Basic reachability
`dig`	`dig +short api.example.com`	DNS lookup
`traceroute`	`traceroute host`	Path debugging
`curl`	`curl -vI https://host`	HTTP/TLS probe

Remote & sync

Command	Example	Use when
`ssh`	`ssh -J bastion target`	Jump host access
`rsync`	`rsync -avz --delete src/ host:dest/`	Incremental deploy
`rsync`	`rsync -av --dry-run src/ dest/`	Preview sync
`scp`	`scp -r certs/ host:/etc/ssl/`	Quick file push

Storage & mounts

Command	Example	Use when
`lsblk`	`lsblk -f`	Block devices + FS type
`blkid`	`blkid /dev/sdb1`	UUID for fstab
`mount`	`mount /dev/sdb1 /mnt`	Attach filesystem
`umount`	`umount -l /mnt`	Lazy unmount if busy
`df`	`df -hT`	Space + FS type
`du`	`du -xh --max-depth=1 /`	Find large dirs

Performance

Command	Example	Use when
`top`	`top -o %CPU`	CPU hogs
`htop`	`htop`	Interactive process view
`free`	`free -h`	RAM & swap
`vmstat`	`vmstat 1 5`	CPU/mem/io snapshot
`iostat`	`iostat -xz 1`	Disk saturation
`uptime`	`uptime`	Load averages
`dmesg`	`dmesg -T \| tail`	Kernel errors (OOM, disk)

Debugging

Command	Example	Use when
`strace`	`strace -c -p $PID`	Syscall summary for stuck proc
`lsof`	`lsof -i :443`	Who holds port
`lsof`	`lsof +L1`	Deleted files still open
`tcpdump`	`tcpdump -i eth0 port 443`	Packet capture (if installed)
`nmap`	`nmap -sV localhost`	Local port scan audit

System identity

Command	Example	Use when
`uname`	`uname -a`	Kernel/arch
`hostnamectl`	`hostnamectl`	Host + OS metadata
`lscpu`	`lscpu`	CPU topology
`timedatectl`	`timedatectl`	NTP/timezone issues

Pro Tip: Need full syntax and more examples? Use the Commands Reference search. For script patterns see Shell & Scripting.