I have posted about commands in the past. I am now ‘rebooting’ that post adding additional commands that I find useful.
File Transfer:
$ scp somefile.txt server:/tmp Secure copies somefile.txt to remote host /tmp folder
$ scp sysadmin@server:/www/*.html /www/tmp Copies *.html files from remote host to current system /www/tmp folder
$ scp -r sysadmin@server:/www /www/tmp Copies all files and folders recursively from remote server to the current system /www/tmp folder
$ rsync -a /home/backup /backup/ Synchronizes source to destination
File and Folder Archive:
$ tar cf home.tar home Creates tar named home.tar containing home/
$ tar xf file.tar Extracts the files from file.tar
$ tar czf file.tar.gz files Creates a tar with gzip compression
$ gzip file Compresses the file and renames it to file.gz
Networking Stuff:
$ ifconfig -a Display all network ports and ip address
$ ifconfig eth0 Display specific ethernet port ip address and details
$ ip addr show Display all network interfaces and ip address(available in iproute2 package,powerful than ifconfig)
$ ip address add 10.0.0.1 dev eth0 Set ip address
$ ethtool eth0 Linux tool to show ethernet status
$ mii-tool eth0 Linux tool to show ethernet status
$ ping host Sends echo request to test connection
$ whois domain Get who is information for domain
$ dig domain Get DNS information for domain
$ dig -x host Reverse lookup host
$ host google.com Lookup DNS ip address for the name
$ hostname -i Lookup local ip address
$ wget file Download file
$ netstat -tupl Listing all active listening ports(tcp,udp,pid)
$ ssh user@host Connects to host as user
$ ssh -p port user@host Connects to host using specific port
$ telnet host Connects to the system using telnet port
Permissions:
$ chmod 777 /data/test.c Sets rwx permission for owner , rwx permission for group, rwx permission for world
$ chmod 755 /data/test.c Sets rwx permission for owner,rx for group and world
$ chown owner-user file Changes the owner of the file
$ chown owner-user:owner-group file-name Changes the owner and group owner of the file
$ chown owner-user:owner-group directory Changes the owner and group owner of the directory
Process Management:
$ ps Displays your currently active processes
$ ps aux | grep ‘telnet’ Finds all process id related to telnet process
$ pmap Memory map of process
$ top Display all running processes
$ kill pid Kill process with mentioned pid id
$ killall proc Kill all processes named proc
$ sleep 10 & Sleeps at the background
$ kill ‘JobNumber ‘ Terminates the job
$ jobs Display the jobs
$ pkill processname Send signal to a process with its name
$ bg Resumes suspended jobs without bringing them to foreground
$ fg Brings the most recent job to foreground
$ fg n Brings job n to the foreground
Useful File Commands:
$ cd .. To go up one level of the directory tree
$ cd Goes to $HOME directory
$ cd /test Changes to /test directory
$ ls gives the contents of a folder.
$ ls -a gives all the contents of a folder.
$ mkdir FolderName creates the folder FolderName.
$ cd Directory makes the Directory current directory
$ pwd prints the working directory
$ cp ~/Desktop/Berk/backups/science.txt . copy science.txt to the current directory
$ mv backups/science.txt /Desktop/Emi moves science.txt to folder Emi
$ rm temp.txt removes the temp.txt file
$ clear clear screen
$ cat science.txt Display contents of a file on the screen
$ less science.txt Displays on a different page ( type q to close the page)
$ less science.txt and then /name finds the occurences of name
$ head science.txt displays the first ten lines of the file
$ tail science.txt displays the last ten lines of the file
$ tail -20 science.txt displays the last 20 lines of the file
$ grep ‘searchedkeyword’ science.txt searches and finds the keyword in the file.(case sensitive)
$ grep -i SeaRchEdKeyWoRd science.txt case insensitive search
$ grep -i ‘SeaRched Sentence is this one’ science.txt case insensitive search
instead of i we can use;
-n precede each matching line with the line number
-v display those lines that do not match
-c print only the total count of matching lines
$ find -name “*.txt” -print finds the text files in the current directory
$ diff a.txt b.txt gives the different lines
$ wc -w science.txt gives the word count
$ wc -l science.txt gives the line count
$ cat > list1
pear
banana
…
ctrl+d
creates a list and we can print this list by using:
$ cat list1 command line.
$ cat biglist | grep p | sort gives sorted list elements which include p
$ sort < biglist > sortedlist sorts the biglist and writes it to the sortedlist
$ ls list* outputs the filenames starting with ‘list’
$ ls *list outputs the filenames ending with ‘list’
$ ls ?un outputs the filenames ending with ‘un’ but just one letter. (e.g. sun, gun, bun)
$ man ____ gives information about the command in the underlined section.
$ whatis ____ gives information about the command in the underlined section.
$ ls -l gives detailed information about the gfiles in the directory
u:user
g:group
o:other people
rwx: read write execute
rw: read write
r: read
x: execute
$ chmod u+x TheFile adds writing permission to the user(owner) of TheFile
$ chmod go-rwx biglist to remove read write and execute permissions on the file biglist for the group and others
$ chmod 754 TheFile 7, 5, 4 represents the individual permissions for user, group, other (7:rwx, 5:rx, 4:r)
4 – stands for “read”
2 – stands for “write”
1 – stands for “execute”
0 – no permissions
$ du -s * The du command outputs the number of kilobyes used by each subdirectory.
$ df . The df command reports on the space left on the file system.
$ gzip science.txt Compresses into a gzip file
$ gunzip science.txt.gz De-compresses into the original file
$ tar cvf New.tar addthisfileintotar Create a tar file called New and add this file.
$ tar xvf New.tar Extracts the tar file
$ zcat science.txt.gz reads zipped files without unzipping
$ file * Classifies the files in the current directory ( folder, text, gzip, etc.)
$ name=Berk
$ echo Hello $name Prints ‘Hello Berk’
$ sha1sum FileName | grep e509760917361307015 Compares the checksum of a downloaded file and the calculated one.
$ gpg -c file Encrypts file
$ gpg file.gpg Decrypts file
User Related:
$ id Shows the active user id with login and group
$ last Shows last logins on the system
$ who Shows who is logged on the system
$ groupadd admin Adds group “admin”
$ useradd -c “Jermal Smith” -g admin -m sam Creates user “sam” and adds to group “admin”
$ userdel sam Deletes user sam
$ adduser sam Adds user “sam”
$ usermod Modifies user information
System Statistics:
$ top Displays the top CPU processes (Ctrl+C to exit)
$ vmstat 2 Displays virtual memory statistics
$ sudo tcpdump -i eth0 Captures all packets flows on interface eth0
$ sudo tcpdump -i eth0 ‘port 80’ Monitors all traffic on port 80 ( HTTP )
$ lsof Lists all open files belonging to all active processes.
$ lsof -u myuser Lists files opened by specific user
$ watch df -h Shows changeable data continuously
System Info:
$ uname -a Displays Linux system information
$ uname -r Displays kernel release information
$ uptime Shows how long system running + load
$ hostname Shows system host name
$ hostname -i Displays the IP address of the host
$ last reboot Shows system reboot history
$ date Shows the current date and time
$ cal Shows this month calendar
$ whoami Shows who you are logged in as
Hardware Info:
$ dmesg Detected hardware and boot messages
$ cat /proc/meminfo Hardware memory information
$ cat /proc/cpuinfo CPU model information
$ cat /proc/interrupts Lists the number of interrupts per CPU per I/O device
$ sudo lshw Displays information on hardware configuration of the system
$ lsblk Displays block device related information in Linux (sudo yum install util-linux-ng)
$ free -m Displays used and free memory (-m for MB)
$ lsusb -tv Shows USB devices
$ dmidecode Shows hardware info from the BIOS
$ hdparm -i /dev/sda # Shows info about disk sda
$ hdparm -tT /dev/sda # Do a read speed test on disk sda
$ badblocks -s /dev/sda # Test for unreadable blocks on disk sda