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linux

System Management 1 Logging 1 Process Management 2 Networking 3 Storage 2 File Management 1 Text Processing 3

linux Commands

System Management

systemctl

Control systemd system and service manager.

systemd services system-management 

systemctl
Examples:
Start a service 
systemctl start nginx
Check service status 
systemctl status nginx
Enable service on boot 
systemctl enable nginx

Logging

journalctl

Query and display messages from the journal.

logs journal systemd 

journalctl
Examples:
View recent logs 
journalctl -n 50
Follow logs in real-time 
journalctl -f
View logs for a specific service 
journalctl -u nginx

Process Management

ps

Report a snapshot of the current processes.

processes monitoring 

ps
Examples:
Show all processes 
ps aux
Show processes for a user 
ps -u username
Show process tree 
ps -ejH
top

Display Linux processes in real-time.

processes monitoring real-time 

top
Examples:
Start top 
top
Show processes for specific user 
top -u username

Networking

netstat

Print network connections, routing tables, interface statistics.

networking connections ports 

netstat
Examples:
Show listening ports 
netstat -tlnp
Show all connections 
netstat -an
ss

Show socket statistics (modern replacement for netstat).

networking sockets connections 

ss
Examples:
Show listening ports 
ss -tlnp
Show all connections 
ss -an
iptables

Administration tool for IPv4 packet filtering and NAT.

firewall networking security 

iptables
Examples:
List all rules 
iptables -L -n -v
Allow incoming SSH 
iptables -A INPUT -p tcp --dport 22 -j ACCEPT

Storage

df

Show disk space usage.

disk storage space 

df
Examples:
Show disk usage in human readable format 
df -h
Show inode usage 
df -i
du

Estimate file space usage.

disk storage usage 

du
Examples:
Show directory sizes 
du -sh /var/*
Show largest directories 
du -sh /* | sort -hr

File Management

find

Search for files in a directory hierarchy.

files search locate 

find
Examples:
Find files by name 
find / -name "*.log"
Find files modified in last 7 days 
find / -mtime -7
Find and delete old files 
find /tmp -mtime +30 -delete

Text Processing

grep

Search for patterns in files.

search text pattern 

grep
Examples:
Search for text in files 
grep -r "error" /var/log
Search with case insensitive 
grep -i "error" file.txt
Show line numbers 
grep -n "pattern" file.txt
sed

Stream editor for filtering and transforming text.

text editing transformation 

sed
Examples:
Replace text in file 
sed 's/old/new/g' file.txt
Delete lines containing pattern 
sed '/pattern/d' file.txt
awk

Pattern scanning and text processing language.

text processing pattern 

awk
Examples:
Print specific field 
awk '{print $1}' file.txt
Sum values in column 
awk '{sum += $1} END {print sum}' file.txt