Master Essential Linux Commands for File, Directory, and System Management

Linux Common Commands

ls – List directory contents. Usage examples: ls (current directory), ls -l (long format), ls -a (all files including hidden), ls -al (long format with hidden), ls -h (human‑readable sizes), ls -d (show directory itself).

cd – Change directory. Examples: cd /usr/local/src (absolute path), cd ~ (home), cd - (previous), cd .. (parent), cd . (current).

pwd – Print working directory.

Directory Operations Commands

mkdir – Create directories. mkdir test creates a directory, mkdir -p test1/test2/test3 creates nested directories.

rmdir – Remove empty directories.

File Operations Commands

touch – Create an empty file or update timestamps. touch test.py.

rm – Remove files or directories. rm file, rm -r dir (recursive), rm -f file (force), rm -rf dir (force recursive).

cp – Copy files or directories. cp source target, cp -r source_dir target_dir, cp -p source target (preserve attributes), cp -a source target (archive mode).

mv – Move or rename files/directories. mv source target, mv /root/test /tmp/, mv /root/test newtest.

cat – Display file contents. cat file, cat -n file (with line numbers).

more – Paginated view of file contents. Use space to advance, b to go back, q to quit.

head – Show the beginning of a file. head file (default 10 lines), head -n 20 file, head -n -20 file (last 20 lines).

ln – Create links. ln -s source target creates a symbolic link.

Permission Management

chmod – Change file permissions. Symbolic examples: chmod u+x file, chmod g+w,o+w file, chmod u=rwx file. Numeric examples: chmod 755 file, chmod 644 file.

chown – Change file ownership. chown user file, chown user:group file.

User Operations

useradd username

– Add a new user. passwd username – Set user password.

Help Commands

man – View manual pages. --help – Show command help.

Search Commands

whereis – Locate command binaries and manuals. find – Search files with options like -name, -user, -size, -type, -perm, -iname. grep – Search for patterns in files. Options: -i (ignore case), -v (invert match). Example: grep -i "root" /etc/passwd. Use pipelines, e.g., cat file | grep "text" or ls -l /etc | more.

Compression and Decompression

Common formats: .gz, .bz2. Archive commands: tar -zcvf archive.tar.gz files (create gzipped archive). tar -zxf archive.tar.gz (extract). tar -jcvf archive.tar.bz2 files (create bzip2 archive). tar -jxf archive.tar.bz2 (extract). List contents without extracting: tar -ztvf archive.tar.gz, tar -jtvf archive.tar.bz2. Use -C /path to specify extraction directory.

Shutdown and Reboot Commands

shutdown – Power off or reboot. shutdown -h now (halt), shutdown -r now (reboot).

reboot – Reboot the system.

Mount Commands

mount – Mount storage devices. Example: mount -t iso9660 /dev/cdrom /mnt/cdrom. umount – Unmount devices. Example: umount /dev/cdrom or umount /mnt/cdrom (ensure you leave the mount point first).

Network Commands

ping – Test network connectivity. ping -c 4 8.8.8.8 sends four packets. ifconfig – Display or configure network interfaces (requires root).