Linux Commands Cheat Sheet: Find, Permissions, Disk & More

Find Command

The find command is one of the most powerful tools in Linux for locating files and directories.

Find Files by Name

# Find files by name (case-sensitive)
find /path/to/search -name "filename.txt"

# Find files by name (case-insensitive)
find /path/to/search -iname "*.log"

# Find in current directory
find . -name "*.js"

Find by Type

# Find only directories
find . -type d -name "config"

# Find only files
find . -type f -name "*.md"

# Find symbolic links
find . -type l

Find and Execute Commands

# Find and delete files
find . -name "*.tmp" -delete

# Find and execute a command on each file
find . -name "*.log" -exec rm {} \;

# Find and grep within files
find . -name "*.js" -exec grep -l "TODO" {} +

# Find files containing specific text
find . -name "config_*" -exec grep "DATABASE" {} +

The + at the end is more efficient than \; as it passes multiple files to grep at once.

File Permissions

Change Directory Permissions

# Set all directories to rwxr-xr-x (755)
find . -type d -exec chmod 755 {} \;

# Set all files to rw-r--r-- (644)
find . -type f -exec chmod 644 {} \;

Understanding Permission Numbers

# Common permission patterns
chmod 755 script.sh    # Owner: all, Group/Others: read+execute
chmod 644 config.txt   # Owner: read+write, Group/Others: read
chmod 600 secrets.key  # Owner only: read+write
chmod +x script.sh     # Add execute permission

Disk Management

View Disk Partitions

# Show disk partitions with filesystem type and labels
sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL

# Detailed disk usage
df -h

# Directory size
du -sh /path/to/directory

# Find largest directories
du -h --max-depth=1 | sort -hr | head -10

Mount Partitions

# Mount a partition read-write (when it's mounted read-only)
mount -o remount,rw /

# Mount USB drive
sudo mount /dev/sdb1 /mnt/usb

# Unmount
sudo umount /mnt/usb

Grep & Text Search

# Search recursively with line numbers
grep -rn "search_term" /path/to/search

# Exclude directories from search
grep -rn "exports" --exclude-dir={node_modules,dist,build} .

# Case-insensitive search
grep -ri "error" /var/log/

# Show only filenames
grep -l "pattern" *.js

# Count matches
grep -c "pattern" file.txt

# Invert match (lines NOT containing pattern)
grep -v "debug" app.log

Creating Patches

Patches are essential for sharing code changes and applying fixes.

# Generate a unified patch between directories
diff -rupN original/ modified/ > changes.patch

# Apply a patch
patch -p1 < changes.patch

# Dry run (test without applying)
patch -p1 --dry-run < changes.patch

# Reverse a patch
patch -R -p1 < changes.patch

The -p1 flag strips the first directory component from file paths in the patch.

Process Management

# Find process by name
ps aux | grep nginx

# Get just the PID
ps aux | grep nginx | awk '{print $2}'

# Or more simply
pgrep nginx

# Kill by name
pkill nginx

# Kill by PID
kill -9 12345

# Monitor processes in real-time
top
htop  # Better alternative (install with: apt install htop)

Library Dependencies

# List symbols in a library
nm -C -n /path/to/libexample.so

# Check shared library dependencies
ldd /path/to/executable

# Find which package provides a file
dpkg -S /usr/bin/curl      # Debian/Ubuntu
rpm -qf /usr/bin/curl       # RHEL/CentOS

Image Manipulation

ImageMagick's convert command is powerful for batch image processing.

# Install ImageMagick
sudo apt install imagemagick

# Resize image
convert input.jpg -resize 800x600 output.jpg

# Resize maintaining aspect ratio
convert input.jpg -resize 800x output.jpg

# Add padding/extend canvas
convert input.jpg -gravity center -extent 1000x1000 output.jpg

# Convert format
convert input.png output.jpg

# Batch resize all images
for img in *.jpg; do convert "$img" -resize 50% "resized_$img"; done

Creating Aliases

Add aliases to ~/.bashrc or ~/.bash_aliases for frequently used commands.

# Edit your bashrc
nano ~/.bashrc

# Add aliases
alias ll='ls -la'
alias gs='git status'
alias gp='git pull'
alias dc='docker-compose'
alias k='kubectl'

# Reload bashrc
source ~/.bashrc

System-wide Aliases

# For all users, add to /etc/profile or /etc/bash.bashrc
# Example: safety alias for reboot
alias reboot='echo "Are you sure? Use /sbin/reboot to confirm"'

RPM Package Management

# Reinstall a package
rpm -Uvh --replacepkgs package.rpm

# Query installed packages
rpm -qa | grep nginx

# List files in a package
rpm -ql package-name

# Find which package owns a file
rpm -qf /usr/bin/curl

Quick Reference

Resources

• Bash Beginners Guide
• Linux Man Pages
• ExplainShell - Explains shell commands

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