- ILUG-D - lists.fsci.in

1D1C - watch
by Dhanasekar 23 May '23

23 May '23

watch - execute a program periodically, showing output fullscreen syntax $ watch [option] [command] To Run Command with a Custom Interval $ watch -n 5 free -h $ watch -n 3 date To highlight changes between updates $ watch -d [command] $ watch -d date $ watch -d free -h To exit if there is a change in the output $ watch -g [command] $ watch -g free To hide the watch Command Header $ watch -t date To alert on error $ watch -b [command] regards, T.Dhanasekar

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1D1C - wait
by Dhanasekar 22 May '23

22 May '23

wait - is a built-in command of Linux that waits for completing any running process. syntax $ wait [options] ID To wait for a background process with PID 7872 $ wait 7872 $ rsync -a /home/Documents /tmp/Documents & [1] 78724 $ wait %1 To make waits for any multiple background job to complete and return the job exit status $ wait -n <pid_1> <pid_2> <pid_3> wait command in shell scripts $ vim wait.sh #!/bin/bash sleep 20 & process_id=$! echo "PID: $process_id" wait $process_id echo "Exit status: $?" :x $ sh wait.sh regards, T.Dhanasekar

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1D1C - wall
by Dhanasekar 22 May '23

22 May '23

wall - is used to display a message on the terminals of all logged-in users. syntax $ wall [OPTIONS] [<FILE>|<MESSAGE>] To display a message on the terminals of all logged-in users $ wall "The system will be rebooted in 20 minutes." To suppress the banner and show only the text to the logged-in users $ wall -n "The system will be rebooted in 20 minutes." To write multi-line messages $ wall To pipe the output of another command to wall $ echo "The system will be rebooted in 20 minutes. \nPlease save your work." | wall To broadcast a message from a file $ wall message_from_file.txt To broadcast a message to a group $ wall -g devops "The system will be rebooted in 20 minutes." regards, T.Dhanasekar

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1D1C - vmstat
by Dhanasekar 20 May '23

20 May '23

vmstat - Report virtual memory statistics syntax: $ vmstat [options][delay [count]] To run vmstat without options $ vmstat To Display Active and Inactive System Memory $ vmstat -a To display about memory, event counters, and CPU scheduling statistics $ vmstat -s To display number of forks since boot $ vmstat -f To display Quick Summary Disk Statistics $ vmstat -D To Display Disk Statistics $ vmstat -d To Display Partition Statistics $ vmstat -p vda1 To Display Timestamp Information for Updates $ vmstat -t To use a Delay Value $ vmstat [delay] $ vmstat 4 To use a Count Value $ vmstat [delay[count]] $ vmstat 4 5 To Change Units $ vmstat 3 -S M To Display Statistics for Slabs $ sudo vmstat -m regards, T.Dhanasekar

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1D1C - virsh
by Dhanasekar 19 May '23

19 May '23

Virsh - is a management user interface for virsh guest domains To list a KVM vm guest $ virsh list $ virsh list --all $ virsh list --inactive $ virsh list --uuid $ virsh list --name $ virsh list --state-running $ virsh list --state-paused $ virsh list --persistent $ virsh list --with-snapshot $ virsh list --autostart $ virsh list --help To Check Node info $ virsh nodeinfo To Check Domain Error $ virsh domblkerror <vm_name> To check a domain information $ virsh dominfo <vm_name> To Check Node CPU Stats $ virsh nodecpustats To Check Node Memory Stats $ virsh nodememstats To Check Node hostname $ virsh hostname To start vm $ virsh start <vm_name> To set a vm to start automatically on system startup $ virsh autostart <vm_name> To disable autostart $ virsh autostart --disable <vm_name> To shutdown a running vm $ virsh shutdown <vm_name> To make forceful shutdown of vm $ virsh destroy <vm_name> To restart a vm $ virsh reboot <vm_name> To suspend a vm $ virsh suspend <vm_name> To restore a suspended vm $ virsh resume <vm_name> To save the current state of a vm $ virsh save vm_name vm_name.save To restore saved vm from the file $ virsh restore vm_name.save To create a 3GB volume named vol2 on the default storage pool $ virsh vol-create-as default vol2.qcow2 3G To List volumes $ virsh vol-list --pool default $ virsh vol-list --pool images To attach created volume $ virsh attach-disk --domain <vm_name> \ --source /var/lib/libvirt/images/vol2.qcow2 \ --persistent --target vdb To detach volume $ virsh detach-disk --domain <vm_name> --persistent --live --target vdb To List storage pools $ virsh pool-list To delete volume $ sudo virsh vol-delete vol2.qcow2 --pool default To create a snapshot $ virsh snapshot-create-as \ --domain <vm_name> \ --name "vm_snapshot1" \ --description "vm_name snapshot 1-working" To list available snapshots $ virsh snapshot-list <vm_name> To display info about a snapshot $ virsh snapshot-info --domain <vm_name> --snapshotname vm_snapshot1 To revert the snapshot $ virsh snapshot-revert --domain <vm_name> --snapshotname vm_snapshot1 --running To delete snapshot $ virsh snapshot-delete --domain <vm_name> --snapshotname vm_snapshot1 To clone a vm $ virt-clone --connect qemu:///system \ --original vm_name \ --name vm_name_clone \ --file /var/lib/libvirt/images/vm_name_clone.qcow2 To manage VM vcpus $ virsh setvcpus --domain vm_name --maximum 2 --config $ virsh setvcpus --domain vm_name --count 2 --config To manage VM memory $ virsh setmaxmem <vm_name> 2048 --config $ virsh setmem <vm_name> 2048 --config regards, T.Dhanasekar

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1D1C - vlc
by Dhanasekar 18 May '23

18 May '23

vlc - it is used to play vlc from command line To open vlc from terminal $ vlc & $ vlc /path/to/file.mp3 To play all the files $ vlc -Z * To read in shuffle mode $ vlc -L [files] To repeat the playlist $ vlc -R [files] To Put Video in Full Screen $ vlc --fullscreen [file] regards, T.Dhanasekar

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1D1C - w
by Dhanasekar 17 May '23

17 May '23

w - Show who is logged on and what they are doing syntax $ w [options] [username] w command without options $ w To Display the Short Format $ w -s To List the w Command Output Without Printing the Header $ w -h To ignore usernames when calculating the current process and CPU times $ w -u To Display the IP Address $ w -i To Display in Old Style $ w -o To show remote hostname field $ w -f To print help options $ w --help regards, T.Dhanasekar

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1D1C - virt-install
by Dhanasekar 16 May '23

16 May '23

virt-install - provision new virtual machines To define a name of the VM $ sudo virt-install --name ubuntu20.04 To define CPU for the VM $ sudo virt-install --name ubuntu20.04 --vcpus 2 To define memory for the VM $ sudo virt-install --name ubuntu20.04 --memory 20480 To define OS Variant and OS Type $ sudo virt-install --name ubuntu20.04 --memory 20480 --vcpus=2 --os-type=Linux --os-variant=ubuntu20.04 To assign this default network for VM $ sudo virt-install --name ubuntu20.04 --memory 20480 --vcpus=2 --os-type=Linux --os-variant=ubuntu20.04 \ --location=/tmp/ubuntu20.04.iso --network network=default --graphics=vnc -v regards, T.Dhanasekar

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osinfo-query
by Dhanasekar 15 May '23

15 May '23

osinfo-query - Query information in the database syntax $ osinfo-query [OPTIONS...] TYPE [CONDITION-1 [CONDITION-2 ...]] To List all operating systems $ osinfo-query os To filter specific flavour os $ osinfo-query os vendor="Fedora Project" To filter by fields $ osinfo-query --fields=short-id,version os vendor="Fedora Project" regards, T.Dhanasekar

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1D1C - vimdiff
by Dhanasekar 14 May '23

14 May '23

vimdiff - edit two, three or four versions of a file with Vim and show differences $ cat a.txt this is line 1 this is line 2 this is line 3 this is line 4 $ cat b.txt this is line 1 this is line 2 this is line 3 this is line 5 this is line 6 $ vimdiff a.txt b.txt To split the screen horizontally $ vimdiff -o a.txt b.txt To apply changes from the left file to the right file :diffput To apply changes from the right file to the left file :diffget To undo changes :diffupdate To exit the diff window :qa to exit all the files without saving. :q to exit the files one by one without saving. :wq! to save and exit files one by one. regards, T.Dhanasekar

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