Name: A complete list of commonly used Linux commands
Author: 录屏网

Command code	Notes
arch	Shows the machine's processor architecture (1)
uname -m	Shows the machine's processor architecture (2)
uname -r	Show the kernel version in use
dmidecode -q	Display hardware system components - (SMBIOS/DMI)
hdparm -i /dev/hda	List the architectural features of a disk
hdparm -tT /dev/sda	Perform a test read operation on disk
cat /proc/cpuinfo	Display CPU info information
cat /proc/interrupts	Display interruption
cat /proc/meminfo	Verify memory usage
cat /proc/swaps	Show which swaps are used
cat /proc/version	Show kernel version
cat /proc/net/dev	Show network adapters and statistics
cat /proc/mounts	Show mounted file systems
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 - month, day, hour, minute, year, second
clock -w	Save time modifications to BIOS

Linux Commands — System Shutdown (Shutdown, Restart, and Logout)

Command code	Notes
shutdown -h now	Shut down the system
init 0	Shut down the system
telinit 0	Shut down the system
shutdown -h hours:minutes &	Shut down the system at a scheduled time
shutdown -c	Cancel a scheduled system shutdown
shutdown -r now	Restart
reboot	重启
logout	注销

Linux commands — files and directories

Command code	Notes
cd /home	Enter the '/home' directory'
cd ..	Return to the previous directory
cd ../..	Return to the previous two levels of directory
cd	Enter your personal home directory
cd ~user1	Enter your personal home directory
cd -	Return to the last directory
pwd	Show working path
ls	View files in a directory
ls -F	View files in a directory
ls -l	Show file and directory details
ls -a	Show hidden files
ls [0-9]	Display file and directory names containing numbers
tree	Displays a tree structure of files and directories starting from the root directory
lstree	Displays a tree structure of files and directories starting from the root directory
mkdir dir1	Create a directory called 'dir1'
mkdir dir1 dir2	Create two directories at the same time
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 as well
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 known encodings
iconv -f fromEncoding -t toEncoding inputFile > outputFile	Change character encoding
find . -maxdepth 1 -name *.jpg -print -exec convert	Batch resize files in current directory and send them to thumbnail directory (requires conversion from ImageMagick)

Linux command — file search

Command code	Notes
find / -name file1	Search the root file system for files and directories starting with '/'
find / -user user1	Search files and directories belonging to user 'user1'
find /home/user1 -name \*.bin	Search the directory '/home/user1' for files ending with '.bin'
find /usr/bin -type f -atime +100	Search for executable files that have not been used in the past 100 days
find /usr/bin -type f -mtime -10	Search for files created or modified within 10 days
find / -name \*.rpm -exec chmod 755 '{}' \;	Search for files ending with '.rpm' and define their permissions
find / -xdev -name \*.rpm	Search for files ending with '.rpm', ignoring removable devices such as CD-ROM drives and USB drives
locate \*.ps	Find files ending with '.ps' - run 'updatedb' command first
whereis halt	Display the location of a binary file, source code or man
which halt	Displays the full path to a binary or executable file

Linux Commands — Mount a File System

Command code	Notes
mount /dev/hda2 /mnt/hda2	Mount a disk called hda2 - make sure the directory '/mnt/hda2' already exists
umount /dev/hda2	Unmount a disk called hda2 - first exit from the mount point '/mnt/hda2'
fuser -km /mnt/hda2	Force uninstall when device is busy
umount -n /mnt/hda2	Run an uninstall operation without writing to the /etc/mtab file - useful when the file is read-only or when the disk is full
mount /dev/fd0 /mnt/floppy	Mount a floppy disk
mount /dev/cdrom /mnt/cdrom	Mount a cdrom or dvdrom
mount /dev/hdc /mnt/cdrecorder	Mount a cdrw or dvdrom
mount /dev/hdb /mnt/cdrecorder	Mount a cdrw or dvdrom
mount -o loop file.iso /mnt/cdrom	Mount a file or ISO image file
mount -t vfat /dev/hda5 /mnt/hda5	Mount a Windows FAT32 file system
mount /dev/sda1 /mnt/usbdisk	Mount a USB flash drive or flash memory device
mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share	Mount a windows network share

Linux Commands - Disk Space

Command code	Notes
df -h	Display the list of mounted partitions
ls -lSr \|more	Arrange files and directories by size
du -sh dir1	Estimating disk space used by directory 'dir1'
du -sk * \| sort -rn	Display the size of files and directories in sequence based on capacity
rpm -q -a --qf '%10{SIZE}t%{NAME}n' \| sort -k1,1n	Display the space used by installed rpm packages based on size (fedora, redhat type systems)
dpkg-query -W -f='${Installed-Size;10}t${Package}n' \| sort -k1,1n	Display the space used by installed deb packages based on size (ubuntu, debian system)

Linux Commands — Users and Groups

Command code	Notes
groupadd group_name	Create a new user group
groupdel group_name	Delete a user group
groupmod -n new_group_name old_group_name	Rename 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	Remove a user ('-r' excludes home directory)
usermod -c "User FTP" -g system -d /ftp/user1 -s /bin/nologin user1	Modify user attributes
passwd	Change password
passwd user1	Modify a user's password (only allowed to be executed by root)
chage -E 2020-12-31 user1	Set user password expiration date
pwck	Check '/etc/passwd' for file format and syntax fixes and existing users
grpck	Check '/etc/passwd' for file format and syntax fixes and existing groups
newgrp group_name	Log into a new group to change the default group for newly created files

Linux commands - Permissions on files - use '+' to set permissions and '-' to cancel

Command code	Notes
ls -lh	Show permissions
ls /tmp \| pr -T5 -W$COLUMNS	Divide the terminal into 5 columns for display
chmod ugo+rwx directory1	Sets read (r), write (w), and execute (x) permissions for the directory's owner (u), group (g), and others (o)
chmod go-rwx directory1	Remove the read, write, and execute permissions of the group (g) and others (o) on the directory
chown user1 file1	Change the owner attribute of a file
chown -R user1 directory1	Change the owner attributes of a directory and simultaneously change the attributes of all files in the directory
chgrp group1 file1	Change the group of a file
chown user1:group1 file1	Change the owner and group attributes of a file
find / -perm -u+s	List all files controlled by SUID in a system
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	Disable the SUID bit of a binary file
chmod g+s /home/public	Sets the SGID bit of a directory - similar to SUID, but for directories
chmod g-s /home/public	Disable the SGID bit for a directory
chmod o+t /home/public	Set the STIKY bit on a file - only allows the legitimate owner to delete the file
chmod o-t /home/public	Disable the STIKY bit for a directory

Linux commands - special attributes of files - use "+" to set permissions and "-" to cancel

Command code	Notes
chattr +a file1	Only allowed to read and write files in append mode
chattr +c file1	Allow this file to be automatically compressed/decompressed by the kernel
chattr +d file1	The dump program will ignore this file when doing a file system backup
chattr +i file1	Files set to be immutable cannot be deleted, modified, renamed or linked to
chattr +s file1	Allow a file to be safely deleted
chattr +S file1	Once the application performs a write operation on this file, the system immediately writes the modified results to the disk.
chattr +u file1	If a file is deleted, the system will allow you to recover the deleted file later
lsattr	Show special properties

Linux Commands — Packing and Compressing Files

Command code	Notes
bunzip2 file1.bz2	Unzip a file called 'file1.bz2'
bzip2 file1	Compress a file called 'file1'
gunzip file1.gz	Unzip a file called 'file1.gz'
gzip file1	Compress 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	Unzip rar package
unrar x file1.rar	Unzip rar package
tar -cvf archive.tar file1	Create an uncompressed tarball
tar -cvf archive.tar file1 file2 dir1	Create an archive file containing 'file1', 'file2' and 'dir1'
tar -tf archive.tar	Display 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 compressed package in bzip2 format
tar -jxvf archive.tar.bz2	Decompress a compressed package in bzip2 format
tar -cvfz archive.tar.gz dir1	Create a compressed package in gzip format
tar -zxvf archive.tar.gz	Decompress a compressed package in gzip format
zip file1.zip file1	Create a compressed package in zip format
zip -r file1.zip file1 file2 dir1	Compress several files and directories into a compressed package in zip format at the same time
unzip file1.zip	Unzip a zip format compressed package

Linux commands - RPM packages - (Fedora, Redhat and similar systems)

Command code	Notes
rpm -ivh package.rpm	Install an rpm package
rpm -ivh --nodeeps package.rpm	Install an rpm package ignoring 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 already installed
rpm -e package_name.rpm	Delete an rpm package
rpm -qa	Display all installed rpm packages in the system
rpm -qa \| grep httpd	Display all rpm packages containing "httpd" in their name
rpm -qi package_name	Get special information about an installed package
rpm -qg "System Environment/Daemons"	Display the rpm package of a component
rpm -ql package_name	Display a list of files provided by an installed rpm package
rpm -qc package_name	Display a list of configuration files provided by an installed rpm package
rpm -q package_name --whatrequires	Display a list of dependencies on an rpm package
rpm -q package_name --whatprovides	Display the volume occupied by an rpm package
rpm -q package_name --scripts	Show scripts executed during installation/removal
rpm -q package_name --changelog	Display the modification history of an rpm package
rpm -qf /etc/httpd/conf/httpd.conf	Confirm which rpm package the given file is provided by
rpm -qp package.rpm -l	Display a list of files provided by an rpm package that has not yet been installed
rpm --import /media/cdrom/RPM-GPG-KEY	Import public key digital certificate
rpm --checksig package.rpm	Confirm the integrity of an rpm package
rpm -qa gpg-pubkey	Confirm the integrity of all installed rpm packages
rpm -V package_name	Check file size, permission, type, owner, group, MD5 check and last modified time
rpm -Va	Check all installed rpm packages on the system - use with caution
rpm -Vp package.rpm	Confirm that an rpm package has not been installed yet
rpm2cpio package.rpm \| cpio --extract --make-directories bin	Run an executable file from an rpm package
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 code

Linux command - YUM package upgrader - (Fedora, RedHat and similar systems)

Command code	Notes
yum install package_name	Download and install an rpm package
yum localinstall package_name.rpm	Will install an rpm package, using 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	Delete an rpm package
yum list	List all packages installed on the current system
yum search package_name	Search for packages in the rpm repository
yum clean packages	Clean rpm cache and delete downloaded packages
yum clean headers	Remove all header files
yum clean all	Remove all cached packages and header files

Linux commands - DEB packages (Debian, Ubuntu and similar systems)

Command code	Notes
dpkg -i package.deb	Install/update a deb package
dpkg -r package_name	Remove a deb package from the system
dpkg -l	Display all installed deb packages in the system
dpkg -l \| grep httpd	Display all deb packages containing "httpd" in their name
dpkg -s package_name	Get information about a particular package that has been installed on the system
dpkg -L package_name	Display the file list provided by a deb package that has been installed on the system
dpkg --contents package.deb	Displays a list of files provided by a package that is not yet installed
dpkg -S /bin/ping	Confirm which deb package the given file is provided by

Linux Commands — APT Software Tools (Debian, Ubuntu and similar systems)

Command code	Notes
apt-get install package_name	Install/update a deb package
apt-cdrom install package_name	Install/update a deb package from CD
apt-get update	Upgrade packages in list
apt-get upgrade	Upgrade all installed software
apt-get remove package_name	Delete a deb package from the system
apt-get check	Confirm that the dependent software repository is correct
apt-get clean	Clean cache from downloaded packages
apt-cache search searched-package	Returns the package name containing the search string

Linux command — view file contents

Command code	Notes
cat file1	View the contents of the file forward starting from the first byte
tac file1	View the contents of a file in reverse order starting from the last line
more file1	View the contents of a long file
less file1	Similar to the 'more' command, but it allows reverse operations on files as well as forward operations
head -2 file1	View the first two lines of a file
tail -2 file1	View the last two lines of a file
tail -f /var/log/messages	View content being added to a file in real time

Linux Commands — Text Processing

Command code	Notes
cat file1 \| command( sed, grep, awk, grep, etc...) > result.txt	Merge the detailed description text of one file and write the introduction to a new file
cat file1 \| command( sed, grep, awk, grep, etc...) >> result.txt	Merge the detailed description text of a file and write the introduction to an existing file
grep Aug /var/log/messages	Search for the keyword Aug in the file '/var/log/messages'
grep ^Aug /var/log/messages	Find 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 the directory '/var/log' and subsequent directories for the string Aug
sed 's/stringa1/stringa2/g' example.txt	Replace string1 in the example.txt file with string2
sed '/^$/d' example.txt	Remove all blank lines from example.txt file
sed '/ *#/d; /^$/d' example.txt 从example.txt	Remove all comments and blank lines from the file
echo 'esempio' \| tr '[:lower:]' '[:upper:]'	Merge 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 rows containing only the word string1
sed -e 's/ *$//' example.txt	Remove whitespace characters at the end of each line
sed -e 's/stringa1//g' example.txt	Remove only the word string1 from the document and keep all the rest
sed -n '1,5p;5q' example.txt	View content from line 1 to line 5
sed -n '5p;5q' example.txt	Look at line 5
sed -e 's/00*/0/g' example.txt	Replace multiple zeros with a single zero
cat -n file1	Indicates the number of lines in the file
cat example.txt \| awk 'NR%2==1'	Delete all even lines in example.txt file
echo a b c \| awk '{print $1}'	View the first column of a row
echo a b c \| awk '{print $1,$3}'	Look at the first and third columns of a row
paste file1 file2	Merge the contents of two files or columns
paste -d '+' file1 file2	Merge the contents of two files or two columns, using + in the middle to distinguish them
sort file1 file2	Sort the contents of two files
sort file1 file2 \| uniq	Take the union of two files (only one copy of duplicate lines is kept)
sort file1 file2 \| uniq -u	Remove intersection, leaving other rows
sort file1 file2 \| uniq -d	Take out the intersection of two files (leaving only files that exist in both files)
comm -1 file1 file2	Compare the contents of two files and delete only the contents contained in 'file1'
comm -2 file1 file2	Compare the contents of two files and delete only the contents contained in 'file2'
comm -3 file1 file2	Compare the contents of two files and delete only the parts common to both files

Linux commands - character settings and file format conversion

Command code	Notes
dos2unix filedos.txt fileunix.txt	Convert the format of a text file from MSDOS to UNIX
unix2dos fileunix.txt filedos.txt	Convert the format of a text file from UNIX to MSDOS
recode ..HTML < page.txt > page.html	Convert a text file to html
recode -l \| more	Show all allowed conversion formats

Linux Commands — File System Analysis

Command code	Notes
badblocks -v /dev/hda1	Check for bad blocks on disk hda1
fsck /dev/hda1	Repair/check integrity of linux file system on hda1 disk
fsck.ext2 /dev/hda1	Repair/check integrity of ext2 file system on hda1 disk
e2fsck /dev/hda1	Repair/check integrity of ext2 file system on hda1 disk
e2fsck -j /dev/hda1	Repair/check integrity of ext3 file system on hda1 disk
fsck.ext3 /dev/hda1	Repair/check integrity of ext3 file system on hda1 disk
fsck.vfat /dev/hda1	Repair/check integrity of fat file system on hda1 disk
fsck.msdos /dev/hda1	Repair/check integrity of dos file system on hda1 disk
dosfsck /dev/hda1	Repair/check integrity of dos file system on hda1 disk

Linux command — initialize a file system

Command code	Notes
mkfs /dev/hda1	Create a file system on the hda1 partition
mke2fs /dev/hda1	Create a linux ext2 file system on the hda1 partition
mke2fs -j /dev/hda1	Create a linux ext3 (journaled) 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

Linux Commands — SWAP File System

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

Linux Commands — Backup

Command code	Notes
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	Restoring an interactive backup
rsync -rogpav --delete /home /tmp	Synchronize directories on both sides
rsync -rogpav -e ssh --delete /home ip_address:/tmp	Rsync over SSH channel
rsync -az -e ssh --delete ip_addr:/home/public /home/local	Sync a remote directory to a local directory via ssh and compression
rsync -az -e ssh --delete /home/local ip_addr:/home/public	Sync local directory to remote directory via ssh and compression
dd bs=1M if=/dev/hda \| gzip \| ssh user@ip_addr 'dd of=hda.gz'	Perform a backup of the local disk on the remote host through ssh
dd if=/dev/sda of=/tmp/file1	Back up disk contents to a file
tar -Puf backup.tar /home/user	Perform an interactive backup of the '/home/user' directory
( cd /tmp/local/ && tar c . ) \| ssh -C user@ip_addr 'cd /home/share/ && tar x -p'	Copy the contents of a directory to a remote directory via ssh
( tar c /home ) \| ssh -C user@ip_addr 'cd /home/backup-home && tar x -p'	Copy a local directory in a remote directory via ssh
tar cf - . \| (cd /tmp/backup ; tar xf - )	Copy a directory locally to another place, retaining original permissions and links
find /home/user1 -name '*.txt' \| xargs cp -av --target-directory=/home/backup/ --parents	Find and copy all files ending with '.txt' from one directory to another
find /var/log -name '*.log' \| tar cv --files-from=- \| bzip2 > log.tar.bz2	Find all files ending with '.log' and make a bzip package
dd if=/dev/hda of=/dev/fd0 bs=512 count=1	Perform an action to copy the contents of MBR (Master Boot Record) to a floppy disk
dd if=/dev/fd0 of=/dev/hda bs=512 count=1	Recover MBR contents from backup that has been saved to floppy disk

Linux Commands — CD

Command code	Notes
cdrecord -v gracetime=2 dev=/dev/cdrom -eject blank=fast -force	Erase the contents of a rewritable disc
mkisofs /dev/cdrom > cd.iso	Create an iso image file of the CD on the disk
mkisofs /dev/cdrom \| gzip > cd_iso.gz	Create a compressed CD iso image file on the disk
mkisofs -J -allow-leading-dots -R -V "Label CD" -iso-level 4 -o ./cd.iso data_cd	Create an iso image file of a directory
cdrecord -v dev=/dev/cdrom cd.iso	Burn an ISO image file
gzip -dc cd_iso.gz \| cdrecord dev=/dev/cdrom -	Burn a compressed ISO image file
mount -o loop cd.iso /mnt/iso	Mount an ISO image file
cd-paranoia -B	Rip audio tracks from a CD to wav files
cd-paranoia -- "-3"	Rip audio tracks from a CD to a wav file (parameter -3)
cdrecord --scanbus	Scan bus to identify scsi channel
dd if=/dev/hdc \| md5sum	Verify the md5sum encoding of a device, such as a CD

Linux Commands - Network - (Ethernet and WIFI Wireless)

Command code	Notes
dhclient eth0	Enable 'eth0' network device in dhcp mode
ethtool eth0	Display traffic statistics of network card ‘eth0’
host www.example.com	Find hostnames to resolve names and IP addresses and mirrors
hostname	Show hostname
ifconfig eth0	Display the configuration of an Ethernet card
ifconfig eth0 192.168.1.1 netmask 255.255.255.0	Control IP address
ifconfig eth0 promisc	Set 'eth0' to promiscuous mode to sniff packets (sniffing)
ifdown eth0	Disable an 'eth0' network device
ifup eth0	Enable an 'eth0' network device
ip link show	Display the connection status of all network devices
iwconfig eth1	Display the configuration of a wireless network card
iwlist scan	Show wireless networks
mii-tool eth0	Display the connection status of 'eth0'
netstat -tup	Show all enabled network connections and their PIDs
netstat -tup1	Display all listening network services in the system and their PIDs
netstat -rn	Display the routing table, similar to the "route -n" command
nslookup www.example.com	Find hostnames to resolve names and IP addresses and mirrors
route -n	Show routing table
route add -net 0/0 gw IP Gateway	Control default gateway
route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1	Control the static route to network '192.168.0.0/16'
route del 0/0 gw IP gateway	Delete static route
echo “1”> /proc/sys/net/ipv4/ip_foward	Activate IP forwarding
tcpdump tcp port 80	Show all HTTP loopbacks
whois www.example.com	Search in Whois database

Linux Commands — Microsoft Windows Networking

Command code	Notes
mount -t smbfs -o username=user,password=pass //WinClient/share/mnt/share	挂载一个windows网络共享
nbtscan ip addr	netbios名解析
nmblookup -A ip addr	netbios名解析
smbclient -L ip addr/hostname	显示一台windows主机的远程共享
smbget -Rr smb://ip addr/share	像wget一样能够通过smb从一台windows主机上下载文件

Linux command — IPTABLES(firewall)

Command code	Notes
iptables -t filter -L	Show all links in the filter table
iptables -t nae -L	Display all links in the nat table
iptables -t filter -F	Clean up all rules based on filter table
iptables -t nat -F	Clean up all rules based on NAT table
iptables -t filter -X	Delete all links created by user
iptables -t filter -A INPUT -p tcp --dport telnet -j ACCEPT	Allow telnet access
iptables -t filter -A OUTPUT -p tcp --dport telnet -j DROP	Block telnet access
iptables -t filter -A FORWARD -p tcp --dport pop3 -j ACCEPT	Allow POP3 connections on forwarding links
iptables -t filter -A INPUT -j LOG --log-prefix	Record blocked packets on all links
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE	Set up a PAT (Port Address Translation) on eth0 to mask outgoing packets
iptables -t nat -A POSTROUTING -d 192.168.0.1 -p tcp -m tcp --dport 22-j DNAT --to-destination 10.0.0.2:22	Forward packets destined for one host address to other hosts

Linux commands — monitoring and debugging

Command code	Notes
free -m	List RAM status in megabytes
kill -9 process id	Force close the process and end it
kill -1 process id	Force a process to reload its configuration
last reboot	Show restart history
lsmod	Kernel module that lists status
lsof -p process id	List a list of files opened by a process
lsof /home/user1	List of open files in the given system path
ps -eafw	List linux tasks
ps -e -o pid,args --forest	List linux tasks in a hierarchical manner
pstress	Display program in tree view
smartctl -A /dev/hda	Monitor the reliability of hard drive devices by enabling SMART
smartctl -i /dev/hda	Check whether SMART is enabled on a hard disk device
strace -c ls >/dev/null	List system calls made and use a process to receive them
strace -f -e open ls >/dev/null	List library calls
tail /var/log/dmesg	Display internal events during kernel boot process
tail /val/log/messages	Show system events
top	List the Linux tasks that use the most CPU resources
watch -nl ‘cat /proc/interrupts’	List real-time interrupts

Linux commands — other commonly used commands

Command code	Notes
alias hh='history'	Set an alias for the command history
apropos ...keyword	Make a list of commands including program keywords. This is especially useful when you only know what the program does but don’t remember the commands.
chsh	Change shell command
chsh --list-shells	Nice command to know if you have to connect remotely to another machine
gpg -c filel	Encrypt a file with GNU Privacy Guard
gpg filel.gpg	ASCII code comparison table: online ASCII conversion table, Ascii code comparison table, Ascii code converter, character encoding Ascii conversion,