Linux Command Cheat Sheet: Basic Operations, System Management, and Monitoring

This guide compiles frequently used Linux command-line operations for developers and system administrators, offering quick reference for everyday tasks.

Basic Operations

Shutdown and reboot the system:

shutdown -h now

shutdown -r now

Inspect system and CPU information:

uname -a

cat /proc/version

env

cat /proc/cpuinfo

Create symbolic links: ln -s /usr/local/jdk1.8/ jdk Manage RPM packages: rpm -qa | grep <em>package_name</em> Generate SSH keys: ssh-keygen -t rsa -C [email protected] Define command aliases: alias ll='ls -alF' Synchronize server time: sudo ntpdate -u ntp.api.bz Run commands in background with various logging options:

nohup xxx &

nohup xxx > /dev/null &

nohup xxx > out.log 2>&1 &

Force logout of active users: pkill -kill -t <em>TTY</em> Find command location: which <em>command</em> Check maximum file descriptors: ulimit -n Configure DNS: vim /etc/resolv.conf Query domain routing: nslookup google.com View recent login information: last -n 5 Set static IP address:

ifconfig em1 192.168.5.177 netmask 255.255.255.0

File and Directory Operations

Vim editing shortcuts and commands:

:%s/x/y/g

0

(move to line start) $ (move to line end) shift+g (jump to file end) gg (jump to file start) :set nu (show line numbers) :set nonu (hide line numbers)

Save a read‑only file with sudo: :w !sudo tee % Disk and file size queries:

mount

df

du -H -h

du -sh *

Word count utilities:

wc -l filename

wc -w filename

wc -L filename

wc -c

Compression and extraction:

tar czvf xxx.tar

zip -r xxx.zip

tar zxvf xxx.tar

tar zxvf xxx.tar -C /xxx/yyy/

unzip xxx.zip

Change file ownership: chown eagleye.eagleye xxx.log Copy, remote copy, and directory creation:

cp xxx.log

cp -f xxx.log

cp -r src/ dest/

scp -P <em>port</em> user@host:/path/file /local/path

mkdir -p /xxx/yyy/zzz

Compare files:

diff -u 1.txt 2.txt

Search and Retrieval

Grep examples:

grep -v xxx

grep -n "^$" file

grep -n "^abc" file

grep -c xxx file

grep -i xxx file

Awk field extraction: awk -F ':' '{if ($5 ~ /user/) print $0}' /etc/passwd Find command usage:

find /home/eagleye -name "*.mysql" -print

find /usr -atime 3 -print

find /doc -user jacky -name 'j*' -print

find /doc -name '*bak' -exec rm {} \;

Network Utilities

Identify process using a port: lsof -i:port Get local IP address:

/sbin/ifconfig -a | grep inet | grep -v 127.0.0.1 | grep -v inet6 | awk '{print $2}' | tr -d "addr:"

iptables management:

service iptables status

iptables -I INPUT -s <em>IP</em> -j DROP

iptables -D INPUT -s <em>IP</em> -j DROP

/sbin/iptables -I INPUT -p tcp --dport 9090 -j ACCEPT

Netcat for TCP testing:

nc 192.168.0.11 8000 < data.txt

nc -l 8000 > received_data

nc -lk 8000

Trace network routes: traceroute -I www.163.com Socket inspection with ss and netstat:

ss -l

ss -pl

netstat -n | awk '/^tcp/ {++state[$NF]} END {for (k in state) print k, state[k]}'

Performance Monitoring

Top command sorting tips:

Press F or O then a‑z to sort, R to reverse.

Key fields of top output are described in the accompanying table.

View kernel messages: dmesg Disk I/O statistics: iostat -xz 1 Memory usage: free -m Network throughput: sar -n DEV 1 TCP connection statistics: sar -n TCP,ETCP 1 CPU, memory, and I/O monitoring with vmstat: vmstat 2 1 Interpretation of vmstat columns (r, b, swpd, free, buff, cache, si, so, bi, bo, in, cs, us, sy, id, wa) is provided for performance analysis.