Comprehensive Linux Command Reference and Usage Guide

This guide provides a comprehensive collection of Linux command-line utilities for system administrators and developers, covering a wide range of topics such as system information, shutdown procedures, file and directory operations, searching, mounting, disk usage, user and group management, permissions, special file attributes, compression, package management (RPM, YUM, DEB), backups, networking, and more.

1. Basic Commands

uname -m – display processor architecture.

uname -r – show kernel version.

dmidecode -q – display hardware components.

arch – display machine architecture.

2. Shutdown and Reboot

shutdown -h now – power off immediately.

init 0 or telinit 0 – halt the system.

shutdown -r now or reboot – restart the system.

3. File and Directory Operations

cd /path – change directory.

pwd – print current working directory.

ls , ls -a , ls -l – list files with various options.

mkdir dir , mkdir -p /tmp/dir1/dir2 – create directories.

rm file , rm -rf dir – remove files or directories.

mv source target – move or rename files/directories.

cp source dest , cp -r srcDir destDir – copy files or directories.

4. File Search

find / -name filename – locate files by name.

locate pattern – fast search using updated database.

grep pattern file – search within file contents.

5. Mounting Filesystems

mount /dev/sda1 /mnt/point – mount a device.

umount /mnt/point – unmount.

mount -o loop file.iso /mnt/iso – mount an ISO image.

6. Disk Space and Filesystem Checks

df -h – display mounted filesystems.

du -sh dir – estimate directory size.

fsck /dev/sda1 – check and repair filesystem.

7. User and Group Management

useradd username , userdel username – add or delete users.

groupadd groupname , groupdel groupname – manage groups.

usermod -aG group user – modify user membership.

8. Permissions and Ownership

chmod 755 file – change file mode.

chown user:group file – change owner and group.

chmod +x file – make executable.

9. Special File Attributes

chattr +i file – make immutable.

chattr +a file – allow only appends.

10. Compression and Archiving

tar -cvf archive.tar files – create tar archive.

tar -xvf archive.tar – extract.

tar -czvf archive.tar.gz files – create gzipped tar.

gzip file , gunzip file.gz – compress/decompress.

zip archive.zip files , unzip archive.zip – zip utilities.

11. Package Management (RPM, YUM, DEB)

rpm -ivh package.rpm – install RPM.

rpm -e package – erase RPM.

yum install package , yum update , yum remove package – manage packages on RPM‑based systems.

dpkg -i package.deb , apt-get install package – manage DEB packages.

12. Backup and Synchronization

rsync -avz source/ dest/ – synchronize directories.

dd if=/dev/sda of=backup.img – disk image backup.

tar -cvf backup.tar /home/user – archive backup.

13. Networking

ifconfig eth0 – display interface.

ifup eth0 , ifdown eth0 – enable/disable.

dhclient eth0 – obtain DHCP address.

14. Miscellaneous Utilities

cat, more, less, head, tail – view file contents.

grep, sed, awk – text processing.

date, cal, uptime – system time and status.