My linux command and setting collection 2

kill one user all process
skill -u username
killall -u username

sudo vi /etc/sudoers
add user_name ALL=(ALL) ALL

change your terminal hostname type the following: sudo scutil --set HostName my_new_host_name

~/.ssh/ssh_config

HostName 192.168.0.101
Port 5101

change to bash
type bash in cml
edit /etc/passwd
username:x:1001:1001::/home/username:/bin/bash

grep in subdirectory.
grep -rl  'string'  /path
find /path -name file_name
cancel the post action.  ctrl z.

find out the cpu Hz

lscpu

feh  #image viewer 

#generate a mp4 video from figures

ffmpeg -i tmp_%04d.png -r 4 -vcodec libx264   movie.mp4

# combine pdfs to single one

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/default -dNOPAUSE -dQUIET -dBATCH -dDetectDuplicateImages -dCompressFonts=true -r150 -sOutputFile=output.pdf input.pdf

Reference:

https://askubuntu.com/questions/218567/any-way-to-check-the-clock-speed-of-my-processor
https://unix.stackexchange.com/questions/18043/how-do-i-kill-all-a-users-processes-using-their-uid
https://askubuntu.com/questions/55325/how-to-use-grep-command-to-find-text-including-subdirectories

https://stackoverflow.com/questions/2507766/merge-convert-multiple-pdf-files-into-one-pdf