Useful Linux commands

Some Useful Linux Commands
1) Monitoring

• To see running processes:  ps -f
• To see processes by application name:  ps ax | grep <appname>
• Kill process:  kill -9 <pid>
• Signal to process (for example to restart nginx): kill -s HUP <pid of master nginx>
• Used for monitoring system input/output: iostat
• System-monitor process-view: htop or top
• Used for monitoring network connections: netstat
• sar -P ALL - statitiscs by processor for <cpu, swap, etc> last 24 hours
• free - memory statistics 

2) Files

• Ensure that all directories are 775 

        find /var/www/test -type d | xargs chmod 775 
or
       chmod 0755 $(find . -type d)

• Make all files group and owner readwrite 

      find /var/www/test -type f | xargs chmod o+w,o+r,g+w,g+r

• make sh script executable:
  

      add to beginning of the file #!/bin/bash
      chmod +x <name.sh>

• To see changes in file in real time: tail -f <file name>
• Create symbolic link ln -s <real file location>
• Find file: find ./ -name <searchterm>
• Find in file content find <path> -name "*.php" -print | xargs grep "function testA("
• Text viewer/editor : nano <filename>
• Text viewer/editor : vim <filename>
need to press a - to enter in the editor mode, then press esc - to exit from editor mode, and :qw command to quit and write changes
• File manage: mc
• grep <options> <what to search> <where to search>

        Recursive search grep -r

        Show context grep -C 3

        Show string number grep -n 

•      Sort for example tab delimeter file

       sort -t"$TAB" -k1.4 -nr
       where -t delimeter, -k1.4 -first column from 4th sybmol, -n - numeric sort, -r reverse order

• difference between files

      diff <file1> <file2> -b -B -i -u

      where -b Ignore changes in amount of white space.

     -B Ignore changes that just insert or delete blank lines.

     -i ignore case

     -u unified format

•    To get the lines in one file that are not in another   

         grep -F -x -v -f fileB fileA

This works by using each line in fileB as a pattern (-f fileB) and treating it as a plain string to match (not a regular regex) (-F). You force the match to happen on the whole line (-x) and print out only the lines that don't match (-v). Therefore you are printing out the lines in fileA that don't contain the same data as any line in fileB.

       or

      comm <(sort a) <(sort b) -3

-3 - only that are in file b

-2 - in both files

-1 -only that are in file a

• Compare and find where is first byte and line where difference exists

cmp <file1> <file2>

• extracting gz

gzip -d your_file.gz

or

tar -xvzf your_file.tar

 3) Version Control System

• SVN 

       Copy remote repository  svn checkout https://test.com:8443/svn/Project/trunk ./ --username <name> --password <pass>

       Commit svn commit -m "added howto section."
       Commit with auth svn commit \local\path\to\your\repository --message "release" --no-auth-cache --non-interactive --username user11 --password your_mega_passwd

• GIT

      Copy remote repository git clone https://test.com:8443/svn/Project/trunk

      Commit:

      git commit -a -m "bug fixed"

      git push

or

    git add <changed file>

    git commit -m  "bug fixed" 
    git push

Regex:
match all \r\n - [\r\n]+
https://regexr.com/

4) Docker
docker exec -ti  <image_name> /bin/bash
docker ps
docker restart/stop/start
docker run -it <image_name> /bin/bash


Good posts:
Some Useful Linux Commands
The 10 most useful Linux commands
Five Linux performance commands every admin should know
The Linux Directory Structure, Explained