600 Essential Linux Commands to Solve 99% of Everyday Tasks

1. Basic Commands

uname -m               # Show processor architecture
uname -r               # Show kernel version
dmidecode -q          # Display hardware components
hdparm -i /dev/hda    # List disk characteristics
hdparm -tT /dev/sda   # Perform test reads on a disk
arch                  # Show processor architecture
cat /proc/cpuinfo     # Show CPU info
cat /proc/interrupts # Show interrupts
cat /proc/meminfo     # Check memory usage
cat /proc/swaps       # Show active swap devices
cat /proc/version    # Show kernel version
cat /proc/net/dev    # Show network adapters and stats
cat /proc/mounts     # Show mounted filesystems
lspci -tv            # List PCI devices
lsusb -tv            # Show USB devices
date                 # Show system date
cal 2007             # Show calendar for 2007
date 041217002007.00 # Set date and time (MMDDhhmmYY.ss)
clock -w             # Save BIOS time

2. Shutdown

shutdown -h now      # Power off now (method 1)
init 0               # Power off (method 2)
telinit 0            # Power off (method 3)
shutdown -h HH:MM    # Schedule shutdown
shutdown -c          # Cancel scheduled shutdown
shutdown -r now      # Reboot now
reboot               # Reboot (method 2)
logout               # Log out

3. Files and Directories

cd /home                # Change to /home
cd ..                   # Up one level
cd ../..                # Up two levels
cd ~user1               # Switch to user1's home
cd -                    # Return to previous directory
pwd                     # Print working directory
ls                      # List files
ls -F                   # List with type indicators
ls -l                   # Detailed list
ls -a                   # Show hidden files
ls *[0-9]*              # Show names containing digits
tree                    # Tree view (method 1)
lstree                  # Tree view (method 2)
mkdir dir1              # Create directory dir1
mkdir dir1 dir2         # Create two directories
mkdir -p /tmp/dir1/dir2 # Create nested directories
rm -f file1             # Force delete file1
rmdir dir1              # Remove empty directory
rm -rf dir1             # Remove directory and its contents
mv dir1 new_dir         # Rename/move directory
cp file1 file2          # Copy file
cp dir/* .              # Copy all files from dir to current dir
cp -a /tmp/dir1 .       # Archive copy preserving attributes
ln -s file1 lnk1        # Create symbolic link
ln file1 lnk1          # Create hard link
touch -t 0712250000 file1 # Set timestamp (YYMMDDhhmm)
file file1              # Show MIME type
iconv -l                # List known encodings
iconv -f from -t to inputFile > outputFile # Convert encoding
find . -maxdepth 1 -name *.jpg -print -exec convert "{}" -resize 80x60 "thumbs/{}" \; # Batch resize images

4. File Search

find / -name file1                         # Search from root
find / -user user1                         # Search files owned by user1
find /home/user1 -name \*.bin               # Search .bin files in a home directory
find /usr/bin -type f -atime +100          # Files not accessed in 100 days
find /usr/bin -type f -mtime -10           # Files modified in last 10 days
find / -name \*.rpm -exec chmod 755 '{}' \; # Find RPMs and set permissions
locate \*.ps                               # Locate .ps files (requires updatedb)
whereis halt                               # Locate binary, source, man page
which halt                                 # Show full path of executable

5. Mount a Filesystem

mount /dev/hda2 /mnt/hda2                 # Mount hda2
umount /dev/hda2                          # Unmount hda2
fuser -km /mnt/hda2                       # Force unmount if busy
umount -n /mnt/hda2                       # Unmount without writing /etc/mtab
mount /dev/fd0 /mnt/floppy                 # Mount floppy
mount /dev/cdrom /mnt/cdrom               # Mount CD/DVD
mount -o loop file.iso /mnt/cdrom          # Mount ISO image
mount -t vfat /dev/hda5 /mnt/hda5         # Mount FAT32
mount /dev/sda1 /mnt/usbdisk               # Mount USB stick
mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share # Mount Windows share

6. Disk Space

df -h                                      # Show mounted partitions
ls -lSr | more                             # List files sorted by size
du -sh dir1                                 # Summarize disk usage of dir1
du -sk * | sort -rn                        # Sort directories/files by size
rpm -q -a --qf '%10{SIZE}t%{NAME}n' | sort -k1,1n   # List installed RPMs by size (Fedora/RedHat)
dpkg-query -W -f='${Installed-Size;10}t${Package}n' | sort -k1,1n   # List installed DEBs by size (Debian/Ubuntu)

7. Users and Groups

groupadd group_name      # Create group
groupdel group_name      # Delete group
groupmod -n new old      # Rename group
useradd -c "Name Surname" -g admin -d /home/user1 -s /bin/bash user1 # Add user to admin group
useradd user1           # Add user
userdel -r user1        # Delete user and home directory
usermod -c "User FTP" -g system -d /ftp/user1 -s /bin/nologin user1 # Modify user
passwd                  # Change password
passwd user1            # Change user1's password (root only)
chage -E 2005-12-31 user1 # Set password expiry date
pwck                    # Verify /etc/passwd format
grpck                   # Verify /etc/group format
newgrp group_name       # Switch primary group

8. File Permissions

ls -lh                         # List with human‑readable sizes
chmod ugo+rwx directory1       # Grant rwx to user, group, others
chmod go-rwx directory1       # Remove rwx from group and others
chown user1 file1              # Change owner
chown -R user1 directory1      # Recursively change owner
chgrp group1 file1             # Change group
chown user1:group1 file1        # Change owner and group
find / -perm -u+s             # List files with SUID bit
chmod u+s /bin/file1          # Set SUID on binary
chmod u-s /bin/file1          # Remove SUID
chmod g+s /home/public        # Set SGID on directory
chmod o+t /home/public        # Set sticky bit on directory
chmod +x file                 # Add execute permission for all
chmod -x file                 # Remove execute permission for all
chmod u+x file                # Add execute for owner
chmod ug=wx file              # Owner and group: write & execute only

9. Special File Attributes

chattr +a file1   # Append‑only
chattr +c file1   # Auto‑compress
chattr +d file1   # Exclude from dump backups
chattr +i file1   # Immutable (cannot delete/modify)
chattr +s file1   # Secure deletion
chattr +S file1   # Synchronous updates
chattr +u file1   # Undelete support
lsattr            # List special attributes

10. Packing and Compression

bunzip2 file1.bz2
bzip2 file1
gunzip file1.gz
gzip file1
gzip -9 file1               # Maximum compression
rar a file1.rar test_file
rar a file1.rar file1 file2 dir1
rar x file1.rar
unrar x file1.rar
tar -cvf archive.tar file1
tar -tf archive.tar
tar -xvf archive.tar
tar -cvfj archive.tar.bz2 dir1
tar -cvfz archive.tar.gz dir1
zip file1.zip file1
zip -r file1.zip file1 file2 dir1
unzip file1.zip

11. RPM Packages (Fedora/RedHat)

rpm -ivh package.rpm
rpm -U package.rpm          # Upgrade without changing config
rpm -F package.rpm          # Refresh already‑installed package
rpm -e package.rpm          # Remove package
rpm -qa                     # List all installed RPMs
rpm -q package_name         # Query a package
rpm -ql package_name         # List files provided by package
rpm -V package_name         # Verify package files
rpm --import /path/RPM-GPG-KEY   # Import GPG key

12. YUM Package Manager (Fedora/RedHat)

yum install package_name
yum localinstall package.rpm
yum update package_name
yum remove package_name
yum list
yum search package_name
yum clean all

13. DEB Packages (Debian/Ubuntu)

dpkg -i package.deb
dpkg -r package_name
dpkg -l
apt-get install package_name
apt-get update
apt-get upgrade
apt-get remove package_name
apt-cache search keyword

14. View File Contents

cat file1
tac file1
more file1
less file1
head -2 file1
tail -2 file1
tail -f /var/log/messages

15. Text Processing

grep Aug /var/log/messages
sed 's/string1/string2/g' file.txt
sed '/^$/d' file.txt
tr '[:lower:]' '[:upper:]' <<< "example"
awk '{print $1}' file.txt
sort file.txt | uniq
comm -1 file1 file2

16. Character Set and File Format Conversion

dos2unix filedos.txt fileunix.txt
unix2dos fileunix.txt filedos.txt
recode ..HTML < page.txt > page.html
recode -l | more

17. Filesystem Check

badblocks -v /dev/hda1
fsck /dev/hda1
e2fsck -j /dev/hda1   # For ext3
fsck.vfat /dev/hda1

18. Initialise a Filesystem

mkfs /dev/hda1
mke2fs /dev/hda1
mke2fs -j /dev/hda1   # ext3
mkfs -t vfat /dev/hda5
fdformat -n /dev/fd0
mkswap /dev/hda3

19. SWAP Filesystem

mkswap /dev/hda3
swapon /dev/hda3
swapon /dev/hda2 /dev/hdb3

20. Backup

dump -0aj -f /tmp/home0.bak /home
restore -if /tmp/home0.bak
rsync -rogpav --delete /home /tmp
rsync -az -e ssh user@host:/home /local
dd if=/dev/sda of=/tmp/file1

21. CD/DVD

cdrecord -v dev=/dev/cdrom cd.iso
mkisofs -J -R -V "Label CD" -o ./cd.iso data_cd
mount -o loop cd.iso /mnt/iso
dd if=/dev/hdc | md5sum

22. Network (Ethernet & Wi‑Fi)

ifconfig eth0
ifup eth0
ifdown eth0
ifconfig eth0 192.168.1.1 netmask 255.255.255.0
dhclient eth0
route -n
route add -net 0/0 gw IP_Gateway
hostname
ping www.example.com
netstat -tup
tcpdump tcp port 80
iwlist scan
iwconfig eth1

23. List Directory Contents

ls -a
ls -l
ls -R
ls -ld

24. Determine File Type

file filename

25. Copy, Move, Delete Operations

cp source dest
cp -r src_dir dest_dir
mv old new
rm -f file
rm -r dir
rmdir dir

26. Common System Commands – Display

date
hwclock
cal
uptime

27. VIM Editor

:q            # Quit Vim
i            # Insert mode
Esc          # Return to command mode
dd           # Delete line
yy           # Yank line
p            # Paste after cursor
:u           # Undo
:/pattern    # Search

28. RPM Package Management

rpm -ivh package.rpm          # Install
rpm -e package_name           # Remove (keeps modified configs)
rpm -Uvh package.rpm          # Upgrade
rpm -q package_name           # Query
rpm -ql package_name          # List files installed by package

All commands are presented exactly as they appear in the original article, providing a ready reference for Linux system administrators.