Linux System Administration Commands Reference

System Information

Commands such as arch, uname -m, cat /proc/cpuinfo, lspci -tv, and lsusb -tv display processor architecture, kernel version, CPU details, PCI and USB devices.

Date and Time

Use cal 2007 to show a calendar, date 041217002007.00 to set date/time, and clock -w to write the system clock to BIOS.

Shutdown and Reboot

Shutdown commands include shutdown -h now, init 0, telinit 0, scheduled shutdowns with shutdown -h hh:mm, and reboot with shutdown -r now or reboot. Use logout to log out.

File and Directory Operations

Navigate with cd, list with ls, create directories using mkdir, remove files/directories with rm and rmdir, move/rename with mv, copy with cp, and create links using ln -s (soft) or ln (hard). Additional utilities: tree, lstree, touch, file, iconv.

File Search

Search files with find (e.g., find / -name file1, find /home/user1 -name *.bin) and locate with locate, whereis, which.

Mounting Filesystems

Mount and unmount devices using mount /dev/hda2 /mnt/hda2, umount /dev/hda2, with options for loop devices, ISO images, FAT32, SMB shares, etc.

Disk Space

Check mounted partitions with df -h, list files by size with ls -lSr | more, estimate directory usage with du -sh dir1, and list package sizes using rpm -q -a --qf '%10{SIZE}t%{NAME}n' or dpkg-query -W -f='${Installed-Size;10}t${Package}n'.

User and Group Management

Create groups with groupadd, delete with groupdel, modify with groupmod. Manage users with useradd, userdel, usermod, change passwords with passwd, set expiration with chage -E, and verify files with pwck, grpck, newgrp.

File Permissions

Modify permissions using chmod ugo+rwx directory1, remove with chmod go-rwx directory1, change ownership with chown user1 file1, and set group ownership with chgrp group1 file1. Special bits (SUID, SGID, sticky) are handled with chmod u+s, chmod g+s, chmod o+t, etc.

Special File Attributes

Use chattr +i file1 to make a file immutable, chattr +a for append‑only, chattr +c for compression, and lsattr to view attributes.

Compression and Archiving

Compress/decompress with bzip2, gzip, gunzip, rar, unrar. Create archives using tar -cvf archive.tar file1, tar -czvf archive.tar.gz dir1, tar -cjf archive.tar.bz2 dir1, and extract with tar -xvf. Zip utilities: zip, unzip.

RPM Package Management (Fedora/RedHat)

Install with rpm -ivh package.rpm, update with rpm -U, query with rpm -qa, list files with rpm -ql package, verify with rpm -V package, and import GPG keys with rpm --import.

YUM Package Manager

Install, update, remove packages using yum install, yum update, yum remove, list packages with yum list, search with yum search, and clean caches with yum clean all.

DEB Package Management (Debian/Ubuntu)

Install with dpkg -i package.deb, remove with dpkg -r, list installed packages with dpkg -l, query files with dpkg -L, and locate providing package with dpkg -S /bin/ping.

APT Tools

Manage packages using apt-get install, apt-get update, apt-get upgrade, apt-get remove, and search with apt-cache search.

Viewing File Contents

Use cat, tac, more, less, head, tail, and tail -f for real‑time monitoring.

Text Processing

Combine files with cat, filter with grep, transform with sed (e.g., sed 's/string1/string2/g'), and process columns with awk, paste, sort, uniq, comm.

Character Conversion

Convert line endings with dos2unix and unix2dos, and recode files using recode.

Filesystem Analysis

Check for bad blocks with badblocks -v /dev/hda1 and repair filesystems with fsck, e2fsck, fsck.ext2, fsck.ext3, fsck.vfat, etc.

Filesystem Creation

Create filesystems with mkfs /dev/hda1, mke2fs -j /dev/hda1, mkfs -t vfat 32 -F /dev/hda1, format floppy with fdformat -n /dev/fd0, and create swap with mkswap /dev/hda3.

Swap Management

Enable swap using swapon /dev/hda3 and disable with swapoff.

Backup Utilities

Perform backups with dump and restore with restore, synchronize directories with rsync, create disk images with dd, and archive with tar combined with ssh for remote copies.

CD/DVD Operations

Burn discs with cdrecord, create ISO images with mkisofs, mount ISO files with mount -o loop, and extract audio tracks with cd-paranoia. Verify media using dd if=/dev/hdc | md5sum.

Network Utilities (Ethernet & Wi‑Fi)

Display and configure interfaces with ifconfig, bring interfaces up/down with ifup / ifdown, obtain DHCP leases with dhclient, manage routes with route, resolve names with host, nslookup, view interfaces with ip link show, and monitor traffic with netstat or tcpdump.