#Essential Linux Commands

1# Print working directory
2pwd
3
4# List files
5ls              # Basic list
6ls -l           # Long format
7ls -la          # Include hidden files
8ls -lh          # Human-readable sizes
9ls -lt          # Sort by modification time
10ls -lS          # Sort by size
11
12# Change directory
13cd /var/log     # Absolute path
14cd ..           # Parent directory
15cd ~            # Home directory
16cd -            # Previous directory
17
18# Create directory
19mkdir mydir
20mkdir -p path/to/nested/dir   # Create parent directories
21
22# Remove directory
23rmdir emptydir
24rm -r directory               # Remove recursively
25rm -rf directory              # Force remove (careful!)

1# Create empty file
2touch file.txt
3
4# Copy files
5cp source.txt dest.txt
6cp -r sourcedir/ destdir/     # Copy directory recursively
7cp -p file.txt backup.txt     # Preserve attributes
8
9# Move/rename files
10mv oldname.txt newname.txt
11mv file.txt /path/to/destination/
12
13# Remove files
14rm file.txt
15rm -f file.txt                # Force (no prompt)
16rm -rf directory/             # Recursive force
17
18# Create symbolic link
19ln -s /path/to/original link_name
20
21# Create hard link
22ln /path/to/original link_name

1# View entire file
2cat file.txt
3
4# View with line numbers
5cat -n file.txt
6
7# View beginning of file
8head file.txt
9head -n 20 file.txt           # First 20 lines
10
11# View end of file
12tail file.txt
13tail -n 20 file.txt           # Last 20 lines
14tail -f /var/log/syslog       # Follow (live updates)
15
16# Page through file
17less file.txt
18# Navigation: space=next page, b=back, /=search, q=quit
19
20# View file with syntax highlighting (if bat installed)
21bat file.txt

1# Find by name
2find /home -name "*.txt"
3find . -name "config*"
4
5# Find by type
6find /var -type f             # Files only
7find /var -type d             # Directories only
8
9# Find by size
10find /var -size +100M         # Larger than 100MB
11find /tmp -size -1k           # Smaller than 1KB
12
13# Find by time
14find /var/log -mtime -7       # Modified in last 7 days
15find /tmp -atime +30          # Accessed more than 30 days ago
16
17# Find and execute
18find . -name "*.log" -exec rm {} \;
19find . -name "*.sh" -exec chmod +x {} \;
20
21# Find with multiple conditions
22find . -name "*.txt" -size +1M -mtime -7

1# Fast file search (uses database)
2locate nginx.conf
3
4# Update database
5sudo updatedb

1# Find executable location
2which python
3which nginx
4
5# Find binary, source, and man pages
6whereis nginx

1# Disk usage of current directory
2du -sh .
3du -sh *                      # Each item in directory
4du -h --max-depth=1           # One level deep
5
6# Disk free space
7df -h                         # Human-readable
8df -h /                       # Specific filesystem
9
10# List block devices
11lsblk
12
13# Mount filesystem
14sudo mount /dev/sdb1 /mnt/data
15
16# Unmount
17sudo umount /mnt/data
18
19# Check disk health
20sudo smartctl -a /dev/sda

1# Create archive
2tar -cvf archive.tar directory/
3
4# Create compressed archive (gzip)
5tar -czvf archive.tar.gz directory/
6
7# Create compressed archive (bzip2)
8tar -cjvf archive.tar.bz2 directory/
9
10# Extract archive
11tar -xvf archive.tar
12
13# Extract compressed archive
14tar -xzvf archive.tar.gz
15tar -xjvf archive.tar.bz2
16
17# Extract to specific directory
18tar -xzvf archive.tar.gz -C /path/to/destination
19
20# List contents without extracting
21tar -tvf archive.tar.gz

1# Compress file
2gzip file.txt                 # Creates file.txt.gz
3
4# Decompress
5gunzip file.txt.gz
6gzip -d file.txt.gz
7
8# Create zip archive
9zip -r archive.zip directory/
10
11# Extract zip
12unzip archive.zip
13unzip archive.zip -d /path/to/destination

1# Network interfaces
2ip addr
3ip a                          # Short form
4ifconfig                      # Legacy
5
6# Routing table
7ip route
8route -n                      # Legacy
9
10# DNS lookup
11nslookup google.com
12dig google.com
13host google.com
14
15# Test connectivity
16ping -c 4 google.com
17
18# Trace route
19traceroute google.com
20tracepath google.com
21
22# Open ports and connections
23ss -tuln                      # TCP/UDP listening ports
24netstat -tuln                 # Legacy
25
26# Check port connectivity
27nc -zv host 80
28telnet host 80
29
30# Download files
31curl -O https://example.com/file.txt
32wget https://example.com/file.txt
33
34# HTTP request
35curl https://api.example.com/data
36curl -X POST -d '{"key":"value"}' https://api.example.com/data

1# System info
2uname -a                      # All system info
3hostname                      # Hostname
4hostnamectl                   # Detailed host info
5
6# OS version
7cat /etc/os-release
8lsb_release -a                # If available
9
10# Kernel version
11uname -r
12
13# CPU info
14lscpu
15cat /proc/cpuinfo
16
17# Memory info
18free -h
19cat /proc/meminfo
20
21# Disk info
22lsblk
23fdisk -l
24
25# Running processes
26ps aux
27ps aux | grep nginx
28top                           # Interactive
29htop                          # Better interactive
30
31# System uptime
32uptime
33
34# Who is logged in
35who
36w
37
38# Last logins
39last
40lastlog