crontab

* * * * * <auszuführender Befehl>
┬ ┬ ┬ ┬ ┬
│ │ │ │ │
│ │ │ │ └──── Wochentag (0-7, Sonntag ist 0 oder 7)
│ │ │ └────── Monat (1-12)
│ │ └──────── Tag (1-31)
│ └────────── Stunde (0-23)
└──────────── Minute (0-59)

Beim reboot bzw. nach dem booten ausführen:
@reboot <auszuführender Befehl>

Folgend Schreibweisen sind in der crontab auch möglich:
@daily <auszuführender Befehl>
@midnight <auszuführender Befehl>
@hourly <auszuführender Befehl>
@weekly <auszuführender Befehl>
@monthly <auszuführender Befehl>
@annually <auszuführender Befehl>
@yearly <auszuführender Befehl>

Alle Ausgaben nach /dev/null umleiten:
* * * * * /pfad/script.sh > /dev/null 2>&1

ssh breaks find-loop in shellscript

#!/bin/bash

DIR=/testdir

find ${DIR} -maxdepth 1 -type f | while read FILE ; do
# ohne </dev/null wird die Schleife nach dem ersten ssh beendet
ssh servername "hostname;" </dev/null
done

Scan Network for a Service


		    
nmap -p 22 --open -sV 192.168.0.0/24


                
 
                Scans 192.168.0.1 -  192.168.0.254 for ssh-server (port 22)

                You don't need root access for this


            
            
                PID-File in bash-script
            
            
                PID_FILE=/var/run/scriptname.pid

                

                if [ -f $PID_FILE ]

                then

                    PID=$(cat $PID_FILE)

                    ps -p $PID > /dev/null 2>&1

                    if [ $? -eq 0 ]

                    then

                        echo "Process is already running!"

                        exit 1

                    else

                        ## PID-File exists but process not running -> Update PID-File

                        echo $$ > $PID_FILE

                        if [ $? -ne 0 ]

                        then

                            echo "Error creating PID-file"

                            exit 1

                        fi

                    fi

                else

                    echo $$ > $PID_FILE

                    if [ $? -ne 0 ]

                    then

                        echo "Error creating PID-file"

                        exit 1

                    fi

                fi

                

                # ..... rest of the script

                

                # at the end of the script, remove PID-File

                rm $PID_FILE

            
            
            
                Scrollen im Screen
            
            
                - Press STRG-A

                - Press ESC

                - Scroll with UP and DOWN arrow keys

                - Press ESC to Exit scrollback-mode

            
            

            
                Kill process using grep
            
            


            
                
                        
kill $(ps -ef | grep 'search' | grep -v grep | awk '{print $2}')
 
                
                
or
 
                
                        
ps -ef |grep 'search' | grep -v grep | awk {'print $2'} | xargs kill
 
                
                
or
 
                
                        
pkill -f search
 
                
                
-f The pattern is normally only matched against the process name.  When -f is set, the full command line is used.
 
                

            
	    
            
		get external-ip
            
            


            
                
			
curl ifconfig.me
 
		
            
            
	    
		postfix - recipient address regex rewrite
	    
            

	    
		rewrite localpart like google - remove +something from localpart


		name+something@domain.tld will go to name@domain.tld


		 add file /etc/postfix/recipient_canonical with content:

		
		

		/^(.*)\+(.*)@(.*)$/ ${1}@${3}

		

		

		
 create the db file with postmap

		
		

		postmap /etc/postfix/recipient_canonical

		

		

                
 add to /etc/postfix/main.cf

		
		

		recipient_canonical_maps = regexp:/etc/postfix/recipient_canonical

		

		

		
 reload or restart postfix

		
		

		systemctl restart postfix