February 2023 - ILUG-D - lists.fsci.in

1D1C - ssh
by Dhanasekar 28 Feb '23

28 Feb '23

ssh - is a program for logging into a remote machine and for executing commands on a remote machine To access remote server $ ssh 192.168.122.50 $ ssh my.server.in To specify a username for SSH connection $ ssh username@hostname_or_ip $ ssh -l username@hostname_or_ip $ ssh -l user1(a)192.168.122.50 $ ssh -l user1(a)my.server.in To use a different port number for ssh connection $ ssh my.server.in -p 2222 $ ssh 192.168.122.50 -p 2222 To run a command on a remote server from a local computer $ ssh 192.168.122.50 rm ~/Desktop/test_file.txt To execute multiple commands using SSH on remote nodes $ ssh 192.168.122.50 command1; command2; command3 To make ssh to use protocol version 2 $ ssh -2 user1(a)192.168.122.50 To Print debug information $ ssh -v user1(a)192.168.122.50 To increase the level of verbosity $ ssh -vv user1(a)192.168.122.50 To get more level of verbosity $ ssh -vvv user1(a)192.168.122.50 To enable X11 forwarding with ssh command $ ssh -X ip_address $ ssh -X 192.168.122.50 To hide the error message $ ssh -q 192.168.122.50 To change any default value to other possible values during ssh $ ssh -o option=value ip_address $ ssh -o Port=2222 192.168.122.50 regards, T.Dhanasekar

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1D1C - ss
by Dhanasekar 27 Feb '23

27 Feb '23

ss - is used to dump socket statistics, and to investigate sockets To list all Connections $ ss To list Listening and Non-listening Ports $ ss -a To list Listening Sockets $ ss -l To list all TCP connections $ ss -t To list all listening TCP connections $ ss -lt To list all UDP connections $ ss -ua To list all listening UDP connections $ ss -lu To display PID of sockets $ ss -p To display summary statistics $ ss -s To display IPv4 and IPv6 socket connections $ ss -4 $ ss -6 To filter connections by port number $ ss -at '( dport = :22 or sport = :22 )' $ ss -at '( dport = :80 or sport = :80 )' $ ss -at '( dport = :ssh or sport = :ssh )' $ ss -at '( dport = :http or sport = :http )' regards, T.Dhanasekar

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computer spares/ parts
by PETER REGELOUS 26 Feb '23

26 Feb '23

Hi Mr Dhanasekar Nice to e-meet Are these items of use I have found 1 man who is gifting them! @ , motherboard, cooler, RAM , graphics cards , laptop PSU, 5v 9v 12v power bricks, modem What can we use these for ? Kind regards @ ukX Peter Regelous

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1D1C - split
by Dhanasekar 26 Feb '23

26 Feb '23

split - is used to split large files into smaller files syntax $ split {options} {file_name} {prefix} $ cat example.txt This is line 1 This is line 2 This is line 3 This is line 4 This is line 5 This is line 6 This is line 7 This is line 8 This is line 9 This is line 10 To split example.txt with verbose option $ split example.txt --verbose To split files with customize line numbers $ split -l5 example.txt --verbose To split files with file size $ split -b 4 example.txt --verbose (in bytes) $ split -b 2K <file_name> --verbose (in Kb) $ split -b 2M <file_name> --verbose (in Mb) $ split -b 1G <file_name> --verbose (in Gb) To create Split files with numeric suffix instead of alphabetic $ split -d example.txt --verbose x00 To split file with customize suffix $ split -l5 example.txt ilugc_file To generate n chunks output files $ split -n5 <file_name> To Prevent Zero Size Split output files $ split -n60 -e example.txt To create split output files of customize suffix length $ split -b 4 example.txt -a 3 $ split -b 4 example.txt -a 4 To split ISO file and merge it into a single file $ split -n5 ubuntu-22.04.iso Split_IS0_ it will split ISO file into 5 pieces To merge these files into a single $ cat Split_IS0_a* > ubuntu22.04_new.iso To verify the integrity of merge file using md5sum before split of iso $ md5sum ubuntu22.04.iso after split and merge $ md5sum ubuntu22.04_new.iso regards, T.Dhanasekar

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1D1C - source
by Dhanasekar 25 Feb '23

25 Feb '23

source - is a built-in shell command that reads and executes the file content in the current shell. syntax $ source [filename] [arguments] To pass commands and arguments $ cat example.txt free -h pwd date time uptime $ source example.txt To read variables from a file $ cat example.sh #!/bin/bash VAR1="a" VAR2="b" VAR3="c" create bash script $ cat sample.sh #!/bin/bash source example.sh echo "VAR1 is $VAR1" echo "VAR2 is $VAR2" echo "VAR3 is $VAR3" $ source sample.sh To refresh the current shell environment $ alias ll = 'ls -l' $ alias c = 'clear' $ c $ ll This command only works in the current shell session To make it permanent $ sudo nano ~/.bashrc alias ll = 'ls -l' alias c = 'clear' :x Refresh the current shell environment and make it permanent for the user $ source ~/.bashrc To make it system wide change $ sudo vim /etc/profile alias ll = 'ls -l' alias c = 'clear' :x # source /etc/profile regards, T.Dhanasekar

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1D1C - sort
by Dhanasekar 24 Feb '23

24 Feb '23

sort - is used to sort a file, arranging the records in a particular order. $ cat file.txt assam tamilnadu chattisgarh delhi gujarat himachal pradesh kerala bihar To sort arrange the file.txt $ sort file.txt To Save Output to File $ sort file.txt > sorted.txt To Check for Sorting in File $ sort -c file.txt To Sort Multiple Files $ sort file1.txt file2.txt To Sort in Reverse Order $ sort -r file.txt To Remove Duplicate Entries $ sort -u file.txt To Sort by Months $ ls -l > month.txt $ sort -Mk6 month.txt To Randomly Sort Data $ sort -R sorted.txt regards, T.Dhanasekar

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1D1C - snap
by Dhanasekar 23 Feb '23

23 Feb '23

snap - is used to install, configure, refresh and remove snaps $ sudo snap install snap-store To Install Snap Apps $ sudo snap install <package_name> To list Installed snaps $ snap list To Search for Snaps $ snap find <search_term> To update snaps $ snap refresh <package_name> To print which snap packages have available updates $ sudo snap refresh --list To downgrade Snaps $ sudo snap revert <package_name> To remove Snaps $ sudo snap remove <package_name> To remove a snap without generating a snapshot $ sudo snap remove <package_name> --purge To Disable Snaps $ sudo snap disable <package_name> To Enable a disabled snap $ sudo snap enable <package_name> To List All Running Services $ snap services To list the services of a single snap $ snap services <package_name> To Start, Restart, and Stop Snap Services $ sudo snap restart <package_name> $ sudo snap start <service_name> $ sudo snap stop <package_name> To prevent a snap service from starting on boot $ sudo snap stop --disable <service_name> To make a service to start on next boot $ sudo snap start --enable <service_name> To Download and Install Snap Apps Offline $ snap download <package_name> To display history of changes made to system $ snap changes To change to a different channel $ sudo snap refresh <package_name> --channel=<channel_name> $ sudo snap refresh youtube-dl --channel=stable regards, T.Dhanasekar

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1D1C - slogin
by Dhanasekar 22 Feb '23

22 Feb '23

slogin - is an alias for the ssh client, which is used to connect securely to a remote shell. To login to a remote server $ slogin 192.168.122.50 $ slogin user1(a)192.168.122.50 To login to remote server with port $ slogin -p 22 user1(a)192.168.122.50 To to login as user1 on the remote machine $ slogin -l user1 192.168.122.50 regards, T.Dhanasekar

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1D1C - sleep
by Dhanasekar 21 Feb '23

21 Feb '23

sleep - is used to delay for a fixed amount of time during the execution of any script syntax $ sleep number[suffix] To make sleep command without any suffix $ sleep 20s To display help options $ sleep --help $ cat sleep.sh #!/bin/bash echo "Waiting for 10 seconds..." sleep 10 echo "Task Completed" :x $ sh sleep.sh Waiting for 10 seconds... Task Completed sleep command in the terminal with other commands $ ll && sleep 20 && pwd && free -h regards, T.Dhanasekar

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1D1C - skill
by Dhanasekar 20 Feb '23

20 Feb '23

skill - is used to send signals to users and process To halt/stop user1 $ skill -STOP -u user1 To resume already halted user1 $ skill -CONT -u user1 To kill and logout user1 $ skill -KILL -u user1 To kill and logout all users $ skill -KILL -v /dev/pts/* To stop 3 users user1, user2, user3 $ skill -STOP user1 user2 user3 regards, T.Dhanasekar

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1D1C - size
by Dhanasekar 19 Feb '23

19 Feb '23

size - list section sizes and total size of binary files $ cat hello.c #include <stdio.h> int main() { // printf() displays the string inside quotation printf("Hello, World!"); return 0; } $ gcc hello.c -o hello.o $ size hello.o To display in octal $ size -o hello.o To display in hexadecimal $ size -x hello.o To display in system V format and hexadecimal values $ size -Ax hello.o regards, T.Dhanasekar

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1D1C - shutdown
by Dhanasekar 18 Feb '23

18 Feb '23

shutdown - is used to shutdown the system in a safe way syntax $ shutdown [OPTIONS] [TIME] [MESSAGE] To shutdown the system at a specified time 6 P.M $ sudo shutdown 18:00 To schedule a system shutdown in 30 minutes from now $ sudo shutdown +30 To shutdown the system immediately $ sudo shutdown now To shutdown the system in 30 minutes from now and notify the users with message “system upgrade” $ sudo shutdown +30 "system upgrade" To halt your system $ sudo shutdown -H To make shutdown power-off machine $ sudo shutdown -P To reboot using shutdown $ sudo shutdown -r To specify a time argument and a custom message $ sudo shutdown -r +10 "system upgrade" To cancel a scheduled shutdown $ sudo shutdown -c To cancel a scheduled shutdown, and to broadcast a message to all users $ sudo shutdown -c "reboot is cancelled" regards, T.Dhanasekar

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1D1C - showkey
by Dhanasekar 17 Feb '23

17 Feb '23

showkey - examine the codes sent by the keyboard To examine the codes sent by the keyboard $ sudo showkey To display print options $ sudo showkey -h To start showkey in scan code dump mode $ sudo showkey -s To start showkey in keycode dump mode $ sudo showkey -k To start showkey in `ascii‘ dump mode. $ sudo showkey -a regards, T.Dhanasekar

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1D1C - shuf
by Dhanasekar 16 Feb '23

16 Feb '23

shuf - writes a random permutation of the input lines to standard output shuf command without any option $ shuf 1 2 3 ctrl+d 3 1 2 $ cat file.txt msg1 msg2 msg3 msg4 msg5 msg6 To shuffle all the lines in the file $ shuf file.txt To add the number of lines to shuffle $ shuf -n 3 file.txt To make shuf as a range $ shuf -i 10-30 To get only one output from the randomized range $ shuf -i 10-100 -n 1 To shuffle a range and allow displaying three outputs which can be repetitive. $ shuf -i 10-100 -n 3 -r To use shuf as a List $ shuf -e a b c d $ shuf -e 1 2 3 4 To randomize a list and decide to only output two output lines $ shuf -e -n 2 1 2 3 4 $ shuf -e -n 2 a b c d To write output to a file $ shuf -i 10-20 -o file.txt $ cat file.txt regards, T.Dhanasekar

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1D1C - shred
by Dhanasekar 15 Feb '23

15 Feb '23

shred - overwrite a file to hide its contents, and optionally delete it syntax $ shred [filename] $ shred sample.txt To designate number of times to overwrite a file $ shred -n 2 example.txt To overwrite and delete a file $ shred -uv sample1.txt To selectively overwrite bytes of text $ shred -s [number_of_bytes] [filename] $ shred -s 10 password.txt To run shred with verbose mode $ shred -v file.txt To change permissions to allow writing if necessary $ shred -f [filename] $ shred -f file.txt To hide shredding from the file system. $ shred -z filename $ shred -z file.txt To Display shred Basic Details and Version and help options $ shred --version $ shred --help regards, T.Dhanasekar

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1D1C - shasum
by Dhanasekar 14 Feb '23

14 Feb '23

shasum - Print or Check SHA Checksums syntax $ shasum [OPTION]... [FILE]... $ cat sha_example.txt This is test message for shasum $ shasum sha_example.txt $ sha1sum sha_example.txt $ sha256sum sha_example.txt or $ shasum -a 256 sha_example.txt $ sha512sum sha_example.txt To generate the SHA value for text on the console $ sha256sum -t This is test message (Enter) Ctrl+d regards, T.Dhanasekar

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1D1C - shar
by Dhanasekar 13 Feb '23

13 Feb '23

shar - create a shell archive $ sudo apt install sharutils provides shar package To create a shar archive file. $ shar *.txt > mytext.shar $ shar *.pdf > mypdf.shar $ shar *.mp3 > mymp3.shar $ shar *.c > myc.shar remove all .txt , .pdf , .mp3 , .c files and then, To extract shar archive file $ unshar mytext.shar $ unshar mypdf.shar $ unshar mymp3.shar $ unshar myc.shar regards, T.Dhanasekar

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300 linux commands with examples cheat sheet
by Dhanasekar 12 Feb '23

12 Feb '23

Hi 300 linux commands with examples compiled from 1 Day 1 Command as long cheat sheet upload @ https://github.com/tkdhanasekar/linux_commands_examples/blob/main/linux_300… regards, T.Dhanasekar

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1D1C - sha1sum , sha256sum
by Dhanasekar 12 Feb '23

12 Feb '23

sha1sum - compute and check SHA1 message digest syntax $ sha1sum [OPTION] [FILE_NAME] To create the SHA-1 of a file $ sha1sum example.txt To create the SHA-256 of a file $ sha256sum example.txt To write the SHA-1 of a file to a file $ sha1sum example.txt > example.sha1 add some contents to example.txt and check with $ sha1sum -c example.sha1 example.txt: FAILED sha1sum: WARNING: 1 computed checksum did NOT match updated the SHA-1 file against the example.txt $ sha1sum new.txt > example.sha1 $ sha1sum -c example.sha1 example.txt: OK To forcefully change the command’s capabilities to read in binary mode $ sha1sum -b example.sha1 To print help commands $ sha1sum - -help To get a list of other sha-related commands $ sha regards, T.Dhanasekar

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1D1C - sh
by Dhanasekar 11 Feb '23

11 Feb '23

sh - is a command language interpreter that executes commands read from a command line string, the standard input, or a specified file. To Invoke the Bourne shell $ sh To run the bash script $ sh example.sh regards, T.Dhanasekar

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1D1C - sg
by Dhanasekar 10 Feb '23

10 Feb '23

sg - execute command as different group ID To execute command as different group ID $ sg group-name -c 'command' $ sg dev-group -c 'sleep 100' $ sg admin-group -c 'ping 8.8.8.8' regards, T.Dhanasekar

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1D1C - sftp
by Dhanasekar 09 Feb '23

09 Feb '23

sftp - is a secure remote file transfer utility based on File Transfer Protocol (FTP) To Connect to SFTP $ sftp user(a)192.168.122.50 sftp> To get help commands sftp> help To Check Present Working Directory local working directory sftp> lpwd remote working directory sftp> pwd To List files with sftp On Remote sftp> ls On local machine sftp> lls To upload file using sftp sftp > put sample.py To upload multiple files using sftp sftp > mput *.py To download files using sftp sftp > get example.py To download multiple files using sftp sftp > mget *.pl To switching directories in sftp On Remote sftp > cd Documents on local machine sftp > lcd Documents To create new directory on local sftp > mkdir local_dir To create new directory on remote sftp > lmkdir remote_dir To remove directories using sftp sftp > rm file.txt sftp> rmdir dir1 To exit sftp shell sftp > exit regards, T.Dhanasekar

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1D1C - sfdisk
by Dhanasekar 08 Feb '23

08 Feb '23

sfdisk - display or manipulate a disk partition table To display partitions of all the disks in system $ sudo sfdisk -l To view disk partitions of a specific device $ sudo sfdisk -l /dev/vda To display Total Partition Size $ sudo sfdisk -s To display Partition size of specific partition $ sudo sfdisk -s /dev/vda To dump disk partition details to text file $ sudo sfdisk -d /dev/vda > vda.out To display Disk Geometry for Debugging $ sudo sfdisk -G To display the kernel’s idea of the geometry of the device $ sudo sfdisk -g To display All Disk Partition types $ sudo sfdisk -T To display the partition type of a specific partition $ sudo sfdisk --print-id /dev/vda 1 regards, T.Dhanasekar

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1D1C - setsid
by Dhanasekar 07 Feb '23

07 Feb '23

setsid - run a program in a new session syntax $ setsid [options] program [arguments] $ cat add.sh #!/bin/bash # Take input from user and calculate sum. read -p "Enter first number: " num1 read -p "Enter second number: " num2 sum=$(( $num1 + $num2 )) echo "Sum is: $sum" :x To execute shell script in a new session. $ sudo setsid ./add.sh To set the controlling terminal to the current one. $ sudo setsid -c ./add.sh To wait for the execution of the program to end, and return the exit value of this program as the return value of setsid $ setsid -w ./add.sh regards, T.Dhanasekar

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1D1C - setfacl
by Dhanasekar 06 Feb '23

06 Feb '23

setfacl - set file access control lists syntax $ setfacl option file To modify ACLs of file to give read and write permission to user1 $ setfacl -m u:user1 rw file To remove all extended ACL entries $ setfacl -b file.txt To remove entries from the ACL of file, To remove group 'ilugc' from a file's ACL $ setfacl -x g:ilugc file.txt To remove the default ACL $ setfacl -k file To apply operations to all files and directories recursively $ setfacl -m g:ilugc:rw -R directory To restore a permission backup $ setfacl --restore=file To copy the ACL of one file to another $ getfacl example.txt | setfacl --set-file=- f sample.txt regards, T.Dhanasekar

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ILUG-D February 2023