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

1D1C - unset
by Dhanasekar 30 Apr '23

30 Apr '23

unset - is used to remove variables or functions. syntax $ unset <var-name> $ VAR1='welcomt to linux' $ echo $VAR1 $ unset VAR1 $ echo $VAR1 $ export ILUGC=foss $ printenv ILUGC $ unset ILUGC $ printenv ILUGC regards, T.Dhanasekar

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1D1C - unmkinitramfs
by Dhanasekar 29 Apr '23

29 Apr '23

unmkinitramfs - extract content from an initramfs image syntax $ unmkinitramfs [options] initramfs-file directory To extract the /boot/initrd.img-5.14.0-8-amd64 file into the current working directory $ unmkinitramfs /boot/initrd.img-5.14.0-8-amd64 . To print verbose output $ unmkinitramfs -v /boot/initrd.img-5.14.0-8-amd64 . regards, T.Dhanasekar

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1D1C - unlink
by Dhanasekar 28 Apr '23

28 Apr '23

unlink - is a command-line utility for removing a single file. Call the unlink function to remove the specified FILE syntax $ unlink filename $ unlink dir_name To delete symbolic link $ unlink linkname $ ll lrwxrwxrwx 1 dhana dhana 23 Dec 1 10:08 example.txt -> /home/dhana/example.txt $ unlink example.txt To delete symbolic link directory $ unlink link_dir_name $ ll lrwxrwxrwx 1 dhana dhana 18 Dec 1 10:10 Music -> /home/dhana/Music// $ unlink Music regards, T.Dhanasekar

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1D1C - uniq
by Dhanasekar 27 Apr '23

27 Apr '23

uniq - it is used to report or filter out repeated lines in a file. $ cat demo.txt redhat debian ubuntu ubuntu centos fedora fedora fedora fedora To report or filter out for lines that are adjacent and repeated $ uniq demo.txt To only print unique lines $ uniq -u demo.txt To prefix lines by the number of occurrences $ uniq -c demo.txt To only print duplicate lines, one for each group $ uniq -d demo.txt To print all duplicate lines $ uniq -D demo.txt To print all duplicate lines but allow separating groups with an empty line $ uniq --all-repeated=prepend demo.txt To ignore differences in case when comparing $ uniq -i demo.txt To skip comparing the first X number of characters in each line $ uniq -s 3 demo.txt To compare only the first X number of characters $ uniq -w 4 demo.txt regards, T.Dhanasekar

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1D1C - unexpand
by Dhanasekar 26 Apr '23

26 Apr '23

unexpand - it is used to convert blanks in each FILE to tabs, writing to standard output syntax $ unexpand [OPTION] [FILE] To convert blanks in a file to tabs and write the output to stdout $ unexpand sample.txt To write the output to a file $ unexpand sample.txt > unexpand_output.txt To convert blanks to tabs, reading from standard output $ unexpand To convert all blanks, instead of just initial blanks $ unexpand -a sample.txt To convert only leading sequences of blanks $ unexpand --first-only sample.txt To have tabs a certain number of characters apart $ unexpand -t 4 sample.txt To mention multiple tab positions $ unexpand -t 5,10,15 sample.txt regards, T.Dhanasekar

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1D1C - uncompress
by Dhanasekar 25 Apr '23

25 Apr '23

uncompress - it is used to uncompress files that were compressed using the compress command. $ cat demo.txt This is line one This is line two This is line three This is line four This is line five This is line six This is line seven This is line eight This is line nine This is line ten To compress the file $ compress demo.txt demo.txt.Z To uncompress the file $ uncompress demo.txt.Z To write to the standard output $ uncompress -c demo.txt.Z To print verbose output $ uncompress -v demo.txt.Z To uncompress forcefully $ uncompress -f demo.txt.Z $ uncompress -cvf demo.txt.Z combining with tar command $ tar -cvf - dir1 dir2 | compress > file.tar.Z To uncompress $ uncompress -c file.tar.Z|tar -xvf - regards, T.Dhanasekar

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1D1C - unattended-upgrade/s
by Dhanasekar 24 Apr '23

24 Apr '23

unattended-upgrade - automatic installation of security (and other) upgrades To simulate installing updates, do not actually do it $ sudo unattended-upgrade --dry-run To print debug messages $ sudo unattended-upgrade -d To make apt/libapt print verbose debug messages $ sudo unattended-upgrade --apt-debug -v To print info messages $ sudo unattended-upgrade -v To make Only download, do not even try to install $ sudo unattended-upgrade --download-only To make upgrade in minimal steps $ sudo unattended-upgrade --minimal-upgrade-steps To upgrade all packages together instead of in smaller sets $ sudo unattended-upgrade --no-minimal-upgrade-steps To show this help message $ sudo unattended-upgrade -h regards, T.Dhanasekar

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1D1C - uname
by Dhanasekar 23 Apr '23

23 Apr '23

uname - print system information To print uname without options $ uname To print all information $ uname -a To print the kernel name $ uname -s To print the network node hostname $ uname -n To print the kernel release $ uname -r To print the kernel version $ uname -v To print the machine hardware name $ uname -m To print the processor type $ uname -p To print the hardware platform $ uname -i To print the operating system $ uname -o To display help options and version $ uname -h $ uname --version regards, T.Dhanasekar

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1D1C - umount
by Dhanasekar 22 Apr '23

22 Apr '23

umount - it is used to unmounts a mounted filesystem, informing the system to complete any pending read or write operations, and safely detaching it To unmount all the filesystems mentioned in /etc/mtab $ sudo umount -a To forcefully unmount a filesystem $ sudo umount -f /backup To lazy unmount of a filesystem $ sudo umount -l /backup To unmount a Partition or Filesystem $ sudo umount /mnt To recursively unmount a target with all its children $ sudo umount -R /mnt To umount without writing in /etc/mtab $ sudo umount -n /mnt To unmount more than mount point in a single execution $ sudo umount /mnt /backup regards, T.Dhanasekar

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1D1C - umask
by Dhanasekar 21 Apr '23

21 Apr '23

umask - is used to set default permissions for files or directories the user creates. To calculate umask value $ umask To Displays the current mask $ umask -p To set and update the default umask value $ umask 543 To view symbolic representation $ umask -S To set the default permissions for all new files or folders to 644 and 755 then umask value is $ umask 022 for folders 777-022 = 755 for files 666-022 = 644 regards, T.Dhanasekar

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ILUG-D April 2023