Quick Reference for Common Linux commands

System information

arch Display the processor architecture of the machine (1)
uname -m Display the processor architecture of the machine (2)
uname -r Displays the kernel version in use
dmidecode -q Display hardware system components – (SMBIOS/DMI)
hdparm -i /dev/hda Lists the architectural features of a disk
hdparm -tT /dev/sda Perform a test read on disk
cat /proc/cpuinfo Display CPU info information
cat /proc/interrupts According to the interrupt
cat /proc/meminfo Checking memory usage
cat /proc/swaps Shows which swaps are used
cat /proc/version Displays the kernel version
cat /proc/net/dev Displays network adapters and statistics
cat /proc/mounts The loaded file system is displayed
lspci -tv List PCI devices
lsusb -tv Display USB device

Date Displays the system date

cal 2007 Displays the calendar for 2007
date 20211207131313 Set the date and time – month, day, hour, year. seconds
clock -w Save the time change to BIOS

Shutdown (shutdown, reboot, and logout of the system)

shutdown -h now Shutting down the System (1)
init 0 Shutting down the System (2)
telinit 0 Shutting down the System (3)
shutdown -h hours:minutes & Shut down the system at a predetermined time
shutdown -c Cancel shutting down the system at the scheduled time
shutdown -r now Restart (1)
reboot Restart (2)
logout The cancellation

Files and Directories

cd /home Go to the ‘/ home’ directory
cd .. Returns the upper directory
cd .. /.. Returns the previous two levels of directories
cd Go to your home directory
cd ~user1 Go to your home directory
cd – Returns the directory where you were last time
pwd Show working path
ls View the files in the directory
ls -F View the files in the directory
ls -l Displays file and directory details
ls -a Show hidden files
ls *[0-9]* Displays file names and directory names that contain numbers
tree Displays the tree structure of files and directories starting from the root directory (1)
lstree Displays the tree structure of files and directories starting from the root directory (2)
mkdir dir1 Create a directory called ‘dir1’
mkdir dir1 dir2 Create two directories simultaneously
mkdir -p /tmp/dir1/dir2 Create a directory tree
rm -f file1 Delete a file called ‘file1’
rmdir dir1 Delete a directory called ‘dir1’
rm -rf dir1 Delete a directory called ‘dir1’ and delete its contents simultaneously
rm -rf dir1 dir2 Delete both directories and their contents simultaneously
mv dir1 new_dir Rename/move a directory
cp file1 file2 Copy a file
cp dir/* . Copy all files in a directory to the current working directory
cp -a /tmp/dir1 . Copy a directory to the current working directory
cp -a dir1 dir2 Copy a directory
ln -s file1 lnk1 Create a soft link to a file or directory
ln file1 lnk1 Create a physical link to a file or directory
touch -t 0712250000 file1 Modify the timestamp of a file or directory – (YYMMDDhhmm)
iconv -l List the known codes

File search

find / -name file1 Start with ‘/’ and go to the root file system to search for files and directories
find / -user user1 Search for files and directories belonging to user ‘user1’
find /home/user1 -name *.bin Search for files ending in’.bin’ in the directory ‘/home/user1’
find /usr/bin -type f -atime +100 Searches for executable files that have not been used in the past 100 days
find /usr/bin -type f -mtime -10 Search for files that have been created or modified in the last 10 days
find / -name *.rpm -exec chmod 755 ‘{}’ ; Search for files ending in ‘.rpm’ and define their permissions
find / -xdev -name *.rpm RPM files ending in ‘.rpm’ are searched, ignoring removable devices such as cd-rom drives and flash drives
locate *.ps Find files ending in ‘.ps’ – run the ‘updatedb’ command first
whereis halt Displays the location of a binary, source, or MAN
which halt Displays the full path to a binary or executable file

Mount a file system

df -h Displays a list of mounted partitions
ls -lSr more
du -sh dir1 Estimate the disk space already used by directory ‘dir1’

Users and Groups

groupadd group_name Create a new user group
groupdel group_name Example Delete a user group
groupmod -n new_group_name old_group_name Renames a user group
useradd -c “Name Surname ” -g admin -d /home/user1 -s /bin/bash user1 Create a user belonging to the “admin” user group
useradd user1 Create a new user
userdel -r user1 Delete a user (‘-r’ excludes home directory)
usermod -c “User FTP” -g system -d /ftp/user1 -s /bin/nologin user1 Modifying User Attributes
passwd Change password
passwd user1 Change a user’s password (root only)
chage -E 2005-12-31 user1 Set the validity period of the user password
pwck Check for file format and syntax fixes for ‘/etc/passwd’ and for existing users
grpck Check for file format and syntax fixes for ‘/etc/passwd’ and existing groups
newgrp group_name Log in to a new group to change the default group for newly created files

File permissions

ls -lh Show permissions
ls /tmp pr -T5 -W$COLUMNS
chmod ugo+rwx directory1 Set owner (u), group (g), and other (O) permissions to read (r), write (w), and execute (x) of the directory
chmod go-rwx directory1 Delete the read/write permissions of group (g) and others (O) on directories
chown user1 file1 Change the owner attribute of a file
chown -R user1 directory1 Change the owner properties of a directory and change the properties of all files in the directory
chgrp group1 file1 Change the group of files
chown user1:group1 file1 Change the owner and group properties of a file
find / -perm -u+s List all files in a system that use SUID control
chmod u+s /bin/file1 Set the SUID bit of a binary file – the user running the file is also given the same permissions as the owner
chmod u-s /bin/file1 Disables the SUID bit of a binary file
chmod g+s /home/public Sets the SGID bit of a directory – similar to SUID, but specific to the directory
chmod g-s /home/public To disable the SGID bit of a directory
chmod o+t /home/public Set the STIKY bits of a file – only allow the legal owner to delete the file
chmod o-t /home/public Disable the STIKY bit for a directory

Special properties of the file

chattr +a file1 Only files can be read or written appending
chattr +c file1 Allows this file to be automatically compressed/uncompressed by the kernel
chattr +d file1 This file is ignored by the dump program during a file system backup
chattr +i file1 Set to an immutable file that cannot be deleted, modified, renamed, or linked
chattr +s file1 Allows a file to be safely deleted
chattr +S file1 Once the application writes to the file, cause the system to write the changes to disk immediately
chattr +u file1 If the file is deleted, the system will allow you to restore the deleted file at a later time
lsattr Display special properties

Package and compress files

bunzip2 file1.bz2 Unzip a file called ‘file1.bz2’
bzip2 file1 Zip a file called ‘file1’
gunzip file1.gz Unzip a file called ‘file1.gz’
gzip file1 Zip a file called ‘file1’
gzip -9 file1 Maximum compression
rar a file1.rar test_file Create a package called ‘file1.rar’
rar a file1.rar file1 file2 dir1 Compress ‘file1′,’file2’ and directory ‘dir1’ simultaneously
rar x file1.rar Decompress rar package
unrar x file1.rar Decompress rar package
tar -cvf archive.tar file1 Create an uncompressed tarball
tar -cvf archive.tar file1 file2 dir1 Create a file containing ‘file1′,’file2’, and ‘dir1’
tar -tf archive.tar Displays the contents of a package
tar -xvf archive.tar Release a package
tar -xvf archive.tar -C /tmp Release the compressed package to the/TMP directory
tar -cvfj archive.tar.bz2 dir1 Create a zip package in bzip2 format
tar -jxvf archive.tar.bz2 Unzip a bzip2 package
tar -cvfz archive.tar.gz dir1 Create a gzip zip package
tar -zxvf archive.tar.gz Decompress a gzip package
zip file1.zip file1 Create a zip package in zip format
zip -r file1.zip file1 file2 dir1 Compress several files and directories into a ZIP package
unzip file1.zip Decompress a zip package

RPM package – (Fedora, Redhat, and similar systems)

rpm -ivh package.rpm Install an RPM package
rpm -ivh –nodeeps package.rpm Install an RPM package and ignore dependency warnings
rpm -U package.rpm Update an RPM package without changing its configuration file
rpm -F package.rpm Update an RPM package that is confirmed to be installed
rpm -e package_name.rpm Example Delete an RPM package
rpm -qa All RPM packages installed in the system are displayed
rpm -qa grep httpd
rpm -qi package_name Gets special information about an installed package
rpm -qg “System Environment/Daemons” Displays an RPM package for a component
rpm -ql package_name Displays a list of files provided by an installed RPM package
rpm -qc package_name Displays a list of configuration files provided by an installed RPM package
rpm -q package_name –whatrequires Displays a list of dependencies that exist with an RPM package
rpm -q package_name –whatprovides Display the volume occupied by an RPM package
rpm -q package_name –scripts Displays the script L executed during installation/deletion
rpm -q package_name –changelog Display the change history of an RPM package
rpm -qf /etc/httpd/conf/httpd.conf Verify which RPM package provides the given file
rpm -qp package.rpm -l Displays a list of files provided by an RPM package that has not yet been installed
rpm –import /media/cdrom/RPM-GPG-KEY Import a public key digital certificate
rpm –checksig package.rpm Verify the integrity of an RPM package
rpm -qa gpg-pubkey Verify the integrity of all RPM packages installed
rpm -V package_name Check file size, license, type, owner, group, MD5 check, and last modified time
rpm -Va Check all installed RPM packages on your system – use with care
rpm -Vp package.rpm Verify that an RPM package is not installed
rpm2cpio package.rpm cpio –extract –make-directories *bin*
rpm -ivh /usr/src/redhat/RPMS/arch/package.rpm Install a built package from an RPM source
rpmbuild –rebuild package_name.src.rpm Build an RPM package from an RPM source

YUM Package Upgrader – (Fedora, RedHat and similar systems)

yum install package_name Download and install an RPM package
yum localinstall package_name.rpm An RPM package will be installed and use your own software repository to resolve all dependencies for you
yum update package_name.rpm Update all RPM packages installed in the current system
yum update package_name Update an RPM package
yum remove package_name Example Delete an RPM package
yum list Lists all packages installed on the current system
yum search package_name Search the RPM repository for packages
yum clean packages Clear the RPM cache and delete the downloaded packages
yum clean headers Delete all header files
yum clean all Delete all cached packages and header files

DEB packages (Debian, Ubuntu, and similar systems)

dpkg -i package.deb Install/update a deb package
dpkg -r package_name Delete a DEB package from the system
dpkg -l Displays all deb packages installed on your system
dpkg -l grep httpd
dpkg -s package_name Gets information about a special package that has been installed on the system
dpkg -L package_name Displays a list of files provided by a DEB package that has been installed on your system
dpkg –contents package.deb Displays a list of files provided by a package that has not yet been installed
dpkg -S /bin/ping Verify which DEB package provides the given file

APT software tools (Debian, Ubuntu and similar systems)

apt-get install package_name Install/update a deb package
apt-cdrom install package_name Install/update a deb package from the CD
apt-get update Upgrade software packages in the list
apt-get upgrade Upgrade all installed software
apt-get remove package_name Delete a DEB package from the system
apt-get check Verify that the software repository you depend on is correct
apt-get clean Clear the cache from downloaded packages
apt-cache search searched-package Returns the name of the package containing the string to search for

Viewing file Contents

cat file1 Forward view the contents of the file from the first byte
tac file1 View the contents of a file in reverse, starting with the last line
more file1 View the contents of a long file
less file1 Similar to the ‘more’ command, but it allows the same reverse operation in the file as the forward operation
head -2 file1 Look at the first two lines of a file
tail -2 file1 Look at the last two lines of a file
tail -f /var/log/messages See what is added to a file in real time

Text processing

cat file1 | command( sed, grep, awk, grep, etc…) > result.txt Merges the detailed text of a file and writes the introduction to a new file
cat file1 | command( sed, grep, awk, grep, etc…) >> result.txt Merges the detailed text of a file and writes the introduction to an existing file
grep Aug /var/log/messages Find the key “Aug” in the file ‘/var/log/messages’
grep ^Aug /var/log/messages Look for words starting with “Aug” in the file ‘/var/log/messages’
grep [0-9] /var/log/messages Select all lines containing numbers in the ‘/var/log/messages’ file
grep Aug -R /var/log/* Search for the string “Aug” in the directory ‘/var/log’ and subsequent directories
sed ‘s/stringa1/stringa2/g’ example.txt Replace “string1” with “string2” in example.txt
sed ‘/^$/d’ example.txt Remove all blank lines from example.txt
sed ‘/ *#/d; /^$/d’ example.txt Remove all comments and blank lines from example.txt
echo ‘esempio’ | tr ‘[:lower:]’ ‘[:upper:]’ Merges the contents of upper and lower cells
sed -e ‘1d’ result.txt Exclude the first line from the file example.txt
sed -n ‘/stringa1/p’ View lines that contain only the word “string1”
sed -e ‘s/ *$//’ example.txt Remove the whitespace character at the end of each line
sed -e ‘s/stringa1//g’ example.txt Remove only the word “string1” from the document and keep the rest
Sed – n ‘1, 5 p; 5q’ example.txt Look at lines 1 through 5
sed -n ‘5p; 5q’ example.txt Look at the first row
sed -e ‘s/00*/0/g’ example.txt Replace multiple zeros with a single zero
cat -n file1 Indicates the number of files
cat example.txt | awk ‘NR%2==1’ Delete all even lines in example.txt
echo a b c | awk ‘{print $1}’ Look at the first column of a row
echo a b c | awk ‘{print
1 . 1, 3} ‘		 Look at the first and third columns of a row
paste file1 file2 Combine the contents of two files or columns
paste -d ‘+’ file1 file2 Combine the contents of two files or columns separated by a “+”
sort file1 file2 Sort the capacity of two files
sort file1 file2 | uniq Retrieve the union of two files (only one duplicate line is kept)
sort file1 file2 | uniq -u Delete the intersection and leave the other rows
sort file1 file2 | uniq -d Extract the intersection of two files (leaving only files that exist in both files)
comm -1 file1 file2 Compare the contents of two files and remove only those contained in ‘file1’
comm -2 file1 file2 Compare the contents of two files and remove only those contained in ‘file2’
comm -3 file1 file2 Compare the contents of two files and delete only the parts that are common to the two files

Character Settings and file format conversion

dos2unix filedos.txt fileunix.txt Convert a text file format from MSDOS to UNIX
unix2dos fileunix.txt filedos.txt Convert a text file format from UNIX to MSDOS
recode .. HTML < page.txt > page.html Convert a text file to HTML
recode -l more

File System Analysis

badblocks -v /dev/hda1 Check the bad magnetic block on disk HDA1
fsck /dev/hda1 Fix/check the integrity of the Linux file system on hDA1 disk
fsck.ext2 /dev/hda1 Repair/check the integrity of the ext2 file system on hda1 disk
e2fsck /dev/hda1 Repair/check the integrity of the ext2 file system on hda1 disk
e2fsck -j /dev/hda1 Repair/check the integrity of the ext3 file system on hda1 disk
fsck.ext3 /dev/hda1 Repair/check the integrity of the ext3 file system on hda1 disk
fsck.vfat /dev/hda1 Fix/check the integrity of the FAT file system on hda1 disk
fsck.msdos /dev/hda1 Fix/check the integrity of the DOS file system on hDA1 disk
dosfsck /dev/hda1 Fix/check the integrity of the DOS file system on hDA1 disk

Example Initialize a file system

mkfs /dev/hda1 Create a file system in the HDA1 partition
mke2fs /dev/hda1 Create a Linux ext2 filesystem in the hda1 partition
mke2fs -j /dev/hda1 Create a Linux ext3(journaling) file system in the Hda1 partition
mkfs -t vfat 32 -F /dev/hda1 Create a FAT32 file system
fdformat -n /dev/fd0 Format a floppy disk
mkswap /dev/hda3 Create a swap file system

SWAP file system

mkswap /dev/hda3 Create a swap file system
swapon /dev/hda3 Start a new swap file system
swapon /dev/hda2 /dev/hdb3 Enable two swap partitions

The backup

dump -0aj -f /tmp/home0.bak /home Make a full backup of the ‘/home’ directory
dump -1aj -f /tmp/home0.bak /home Make an interactive backup of the ‘/home’ directory
restore -if /tmp/home0.bak Restore an interactive backup
rsync -rogpav –delete /home /tmp Synchronize directories on both sides
rsync -rogpav -e ssh –delete /home ip_address:/tmp Rsync through SSH channel
rsync -az -e ssh –delete ip_addr:/home/public /home/local Synchronize a remote directory to a local directory using SSH and compression
rsync -az -e ssh –delete /home/local ip_addr:/home/public Synchronize local directories to remote directories using SSH and compression
dd bs=1M if=/dev/hda gzip
dd if=/dev/sda of=/tmp/file1 Backup disk contents to a file
Tar -puf backup.tar /home/user Perform a single call to ‘/home/user’ Interactive backup operations for directories
( cd /tmp/local/ && tar c . ) ssh -C user@ip_addr ‘cd /home/share/ && tar x -p’
( tar c /home ) ssh -C user@ip_addr ‘cd /home/backup-home && tar x -p’
tar cf – . (cd /tmp/backup ; tar xf – )
find /home/user1 -name ‘*.txt’ xargs cp -av –target-directory=/home/backup/ –parents
find /var/log -name ‘*.log’ tar cv –files-from=-
dd if=/dev/hda of=/dev/fd0 bs=512 count=1 Make an action to copy the contents of the MBR (Master Boot Record) to the floppy disk
dd if=/dev/fd0 of=/dev/hda bs=512 count=1 Restores MBR content from a backup already saved to floppy disk

CD

cdrecord -v gracetime=2 dev=/dev/cdrom -eject blank=fast -force Clear the contents of a reproducible CD
mkisofs /dev/cdrom > cd.iso Create an ISO image file on the disk
mkisofs /dev/cdrom gzip > cd_iso.gz
mkisofs -J -allow-leading-dots -R -V “Label CD” -iso-level 4 -o ./cd.iso data_cd Create an ISO image file for a directory
cdrecord -v dev=/dev/cdrom cd.iso Burn an ISO image file
gzip -dc cd_iso.gz cdrecord dev=/dev/cdrom –
mount -o loop cd.iso /mnt/iso Example Mount an ISO image file
cd-paranoia -B Transcribe audio tracks from a CD to a WAV file
cd-paranoia — “-3” Transcribe an audio track from a CD to a WAV file (parameter -3)
cdrecord –scanbus Scan the bus to identify SCSI channels
dd if=/dev/hdc md5sum

Networking – (Ethernet and WIFI wireless)

ifconfig eth0 Displays the configuration of an Ethernet card
ifup eth0 Enable an ‘eth0’ network device
ifdown eth0 Disable an ‘eth0’ network device
Ifconfig eth0 192.168.1.1 netmask 255.255.255.0 Control IP address
ifconfig eth0 promisc Set ‘eth0’ to mingle mode to sniff packets
dhclient eth0 Enable ‘eth0’ in DHCP mode
route -n Viewing the Routing Table
route add -net 0/0 gw IP_Gateway Configuring the Default Gateway
Route add-net 192.168.0.0 netmask 255.255.0.0 GW 192.168.1.1 Configure static route to network ‘192.168.0.0/16’
route del 0/0 gw IP_gateway Deleting a Static Route
hostname View machine name
host www.example.com Resolves a host name to an Internet address or an Internet address to a host name.
nslookup www.example.com It is used to query DNS records to check whether domain names are resolved properly and diagnose network faults.
ip link show Viewing NIC Information
mii-tool Used to view and manage the status of network interfaces on media
ethtool This command is used to query and set NIC configurations
netstat -tupl This command is used to display TCP/UDP status information
tcpdump tcp port 80 Displays all HTTP traffic

If you need the PDF document, please scan the qr code and pay attention to the following qr code

Rumenz.com/examples/li…