Top 100 Linux Commands

Essential Linux commands every sysadmin should know. Organized by category for quick reference.
File & Directory
CommandDescription

lsList directory contents
ls -laList all files with permissions and sizes
cdChange directory
pwdPrint working directory
mkdir -pCreate directory and parents
rm -rfRemove files/directories recursively (use with caution)
cp -rCopy files/directories recursively
mvMove or rename files
find . -nameFind files by name recursively
locateFind files using index (fast)
touchCreate empty file or update timestamp
ln -sCreate symbolic link
du -shShow disk usage of directory
df -hShow disk free space
statShow file metadata (size, inode, timestamps)
File Viewing & Editing
CommandDescription

catPrint file contents
lessPage through file (q to quit)
head -n 20Show first N lines of file
tail -n 20Show last N lines of file
tail -fFollow file in real time (logs)
grep -rnSearch text recursively with line numbers
awkPattern scanning and processing language
sedStream editor — find/replace in files
wc -lCount lines in file
sortSort lines alphabetically or numerically
uniqRemove duplicate lines
cut -d: -f1Cut fields from delimited text
diffCompare two files line by line
vim / nanoTerminal text editors
Permissions & Ownership
CommandDescription

chmod 755Set file permissions (rwxr-xr-x)
chown user:groupChange file owner and group
umaskSet default permission mask
sudoExecute command as superuser
su -Switch to root user
passwdChange user password
idShow current user UID/GID/groups
groupsList user group memberships
Process Management
CommandDescription

ps auxList all running processes
top / htopInteractive process monitor
kill -9 PIDForce kill process by PID
killall nameKill all processes by name
pkillKill processes matching pattern
jobsList background jobs in current shell
bg / fgResume job in background / foreground
nohupRun command immune to hangups
nice / reniceSet process CPU priority
lsofList open files and sockets
straceTrace system calls of a process
Networking
CommandDescription

ip addrShow network interfaces and IPs
ip routeShow routing table
ping -c 4Test connectivity to host
tracerouteTrace network path to host
nslookup / digDNS lookup utilities
curl -IFetch HTTP headers from URL
wgetDownload files from web
ss -tulpnShow open ports and listening services
netstat -anShow network connections
iptables -LList firewall rules
ssh user@hostConnect to remote host via SSH
scp src dstSecure copy files over SSH
rsync -avzSync files/dirs with progress and compression
nmap -sVScan host ports and service versions
tcpdump -i eth0Capture network packets on interface
System Info & Hardware
CommandDescription

uname -aPrint kernel version and system info
uptimeSystem uptime and load average
free -hShow RAM usage in human-readable form
vmstat 1Virtual memory stats every second
iostatCPU and disk I/O statistics
lscpuDisplay CPU architecture information
lsblkList block devices (disks, partitions)
lsusb / lspciList USB and PCI devices
dmesg | tailShow kernel ring buffer / boot messages
hostnamectlShow or set system hostname and OS info
timedatectlShow or set system time and timezone
Package Management
CommandDescription

apt update && apt upgradeUpdate package list and upgrade (Debian/Ubuntu)
apt install pkgInstall a package (Debian/Ubuntu)
apt remove pkgRemove a package
dpkg -lList all installed packages (Debian)
yum / dnf installInstall package (RHEL/CentOS/Fedora)
rpm -qaList all installed RPM packages
Services & systemd
CommandDescription

systemctl status svcCheck service status
systemctl start svcStart a service
systemctl stop svcStop a service
systemctl restart svcRestart a service
systemctl enable svcEnable service at boot
systemctl disable svcDisable service at boot
journalctl -u svcView logs for a specific service
journalctl -fFollow system journal in real time
crontab -eEdit user cron jobs
Archives & Compression
CommandDescription

tar -czvf out.tgz dir/Create gzipped tarball
tar -xzvf file.tgzExtract gzipped tarball
zip -r out.zip dir/Create zip archive
unzip file.zipExtract zip archive
gzip / gunzipCompress / decompress .gz files
Shell & Scripting
CommandDescription

echoPrint text to stdout
export VAR=valSet environment variable
envList all environment variables
aliasCreate command shortcuts
historyShow command history
source / .Execute script in current shell
bash script.shRun a shell script
which / whereisFind location of a command binary
man cmdShow manual page for command
xargsBuild and execute commands from stdin
teeRead from stdin, write to stdout and file

Command	Description
`ls`	List directory contents
`ls -la`	List all files with permissions and sizes
`cd`	Change directory
`pwd`	Print working directory
`mkdir -p`	Create directory and parents
`rm -rf`	Remove files/directories recursively (use with caution)
`cp -r`	Copy files/directories recursively
`mv`	Move or rename files
`find . -name`	Find files by name recursively
`locate`	Find files using index (fast)
`touch`	Create empty file or update timestamp
`ln -s`	Create symbolic link
`du -sh`	Show disk usage of directory
`df -h`	Show disk free space
`stat`	Show file metadata (size, inode, timestamps)

Command	Description
`cat`	Print file contents
`less`	Page through file (q to quit)
`head -n 20`	Show first N lines of file
`tail -n 20`	Show last N lines of file
`tail -f`	Follow file in real time (logs)
`grep -rn`	Search text recursively with line numbers
`awk`	Pattern scanning and processing language
`sed`	Stream editor — find/replace in files
`wc -l`	Count lines in file
`sort`	Sort lines alphabetically or numerically
`uniq`	Remove duplicate lines
`cut -d: -f1`	Cut fields from delimited text
`diff`	Compare two files line by line
`vim / nano`	Terminal text editors

Command	Description
`chmod 755`	Set file permissions (rwxr-xr-x)
`chown user:group`	Change file owner and group
`umask`	Set default permission mask
`sudo`	Execute command as superuser
`su -`	Switch to root user
`passwd`	Change user password
`id`	Show current user UID/GID/groups
`groups`	List user group memberships

Command	Description
`ps aux`	List all running processes
`top / htop`	Interactive process monitor
`kill -9 PID`	Force kill process by PID
`killall name`	Kill all processes by name
`pkill`	Kill processes matching pattern
`jobs`	List background jobs in current shell
`bg / fg`	Resume job in background / foreground
`nohup`	Run command immune to hangups
`nice / renice`	Set process CPU priority
`lsof`	List open files and sockets
`strace`	Trace system calls of a process

Command	Description
`ip addr`	Show network interfaces and IPs
`ip route`	Show routing table
`ping -c 4`	Test connectivity to host
`traceroute`	Trace network path to host
`nslookup / dig`	DNS lookup utilities
`curl -I`	Fetch HTTP headers from URL
`wget`	Download files from web
`ss -tulpn`	Show open ports and listening services
`netstat -an`	Show network connections
`iptables -L`	List firewall rules
`ssh user@host`	Connect to remote host via SSH
`scp src dst`	Secure copy files over SSH
`rsync -avz`	Sync files/dirs with progress and compression
`nmap -sV`	Scan host ports and service versions
`tcpdump -i eth0`	Capture network packets on interface

Command	Description
`uname -a`	Print kernel version and system info
`uptime`	System uptime and load average
`free -h`	Show RAM usage in human-readable form
`vmstat 1`	Virtual memory stats every second
`iostat`	CPU and disk I/O statistics
`lscpu`	Display CPU architecture information
`lsblk`	List block devices (disks, partitions)
`lsusb / lspci`	List USB and PCI devices
`dmesg \| tail`	Show kernel ring buffer / boot messages
`hostnamectl`	Show or set system hostname and OS info
`timedatectl`	Show or set system time and timezone

Command	Description
`apt update && apt upgrade`	Update package list and upgrade (Debian/Ubuntu)
`apt install pkg`	Install a package (Debian/Ubuntu)
`apt remove pkg`	Remove a package
`dpkg -l`	List all installed packages (Debian)
`yum / dnf install`	Install package (RHEL/CentOS/Fedora)
`rpm -qa`	List all installed RPM packages

Command	Description
`systemctl status svc`	Check service status
`systemctl start svc`	Start a service
`systemctl stop svc`	Stop a service
`systemctl restart svc`	Restart a service
`systemctl enable svc`	Enable service at boot
`systemctl disable svc`	Disable service at boot
`journalctl -u svc`	View logs for a specific service
`journalctl -f`	Follow system journal in real time
`crontab -e`	Edit user cron jobs

Command	Description
`tar -czvf out.tgz dir/`	Create gzipped tarball
`tar -xzvf file.tgz`	Extract gzipped tarball
`zip -r out.zip dir/`	Create zip archive
`unzip file.zip`	Extract zip archive
`gzip / gunzip`	Compress / decompress .gz files

Command	Description
`echo`	Print text to stdout
`export VAR=val`	Set environment variable
`env`	List all environment variables
`alias`	Create command shortcuts
`history`	Show command history
`source / .`	Execute script in current shell
`bash script.sh`	Run a shell script
`which / whereis`	Find location of a command binary
`man cmd`	Show manual page for command
`xargs`	Build and execute commands from stdin
`tee`	Read from stdin, write to stdout and file