LINUX - Jobs - Move Running Process to Background & Nohup

LINUX - Jobs - Move Running Process to Background & Nohup

(method 1) ALREADY RUNNING PROCESS INTO BACKGROUND Pro:   Puts running process into background Con:  If you quit out of the shell window the process stops Reference: http://www.unix.com/unix-advanced-expert-users/78975-make-foreground-running-process-run-background-without-hang-up.html 1. Ctrl-z 2. jobs or alternate method which lists the PID (note the PID is not the jobnum, the job number is shell specific to the current bash session): jobs -l 3. bg %jobnum or alternate method %jobnum & for example for the first job %1 & To place a foreground process in the background: suspend the foreground process (with Ctrl-z) then enter the bg command to move the process into the background. Show the status of all background and suspended jobs: jobs Bring a job back into the foreground: fg %jobnumber Bring a job back into the background: bg %jobnumber (method 2 - my favorite) ALREADY RUNNING PROCESS INTO NOHUP Pro:  Puts running process into background, and if you quit out of the shell it still runs Con: Costs a pinch of more memory (a negligiable amount) - I couldnt think of any cons so I had to mention this :-) Reference: http://stackoverflow.com/questions/625409/how-do-i-put-an-already-running-process-under-nohup Using the Job Control of bash to send the process into the background: 0. Run some SOMECOMMAND 1. ctrl+z to stop (pause) the program and get back to the shell 2. bg to run it in the background 3. disown -h so that the process isn't killed when the terminal closes 4. Type exit to get out of the shell because now your good to go as the operation will run in the background in it own process so its not tied to a shell This process is the equivalent of running nohup SOMECOMMAND NOTE1: Example - When running SOMECOMMAND at step 0, if the command outputs alot of text on the screen to where it seems like its overloading you and not accepting your commands - dont worry, just be patient -it actually is taking your commands give a second or two rest in between each step. For example test this command like so:             The seq START FINISH will output every integer from START to FINISH. seq 1 to 5. prints 1 thru 5, with each new  number on a new line. the Tee command outputs to the screen and to a file, so I can simulate the purpose of this NOTE1.             seq 1 10000000 | tee /tmp/file1                     note this command will out put alot of text on the screen             ctrl+z                       once you press ctrl+z wait a second the output should stop, you can confirm the stopped job with        the command "jobs". Also note Once you press ctrl+z the command stops and your presented with the command prompt.             bg                     Once you type bg the heavy amount of screen output will resume - it will seem almost futile to try and enter any  commands, but dont worry, it still accepts your commands its just hard/impossible to see what you enter             disown -h                     After typing disown -h while the text is flowing up the screen you know you put it into that mode                     confirm that it works by exiting the shell             exit                    The command will still run in the background under its own process - just like nohup                 LOG BACK INTO THE SHELL: and check the size of the file a few times - if its increasing then the disown worked and the command is still running                 ls -ls /tmp/ To simulate this type of effect with nohup you could type  nohup seq 1 10000000 | tee /tmp/file1. But the whole point of this exercise is to show you how to put something into the background incase you forgot to nohup it in the beginning. NOTE2: Example - Running SOMECOMMAND at step0, that doesnt output to the screen. This is easier to work with because you can see the disown and exit commands       seq 1 10000000 > /tmp/file2 note the command will not output any text to the screen like before, but you will not be able to put any more commands the command will be gone             ctrl+z                     once you press ctrl+z the command stops and your presented with the command prompt             bg                     Once you type bg you will be presented with a command prompt where you can still type commands freely             disown -h                     The disown -h will put that command into its own process so that you can exit the shell and the command still  runs             exit                    The command will still run in the background under its own process - just like nohup                 LOG BACK INTO THE SHELL: and check the size of the file a few times - if its increasing then the disown worked and the command is still running                 ls -ls /tmp/ To simulate this type of effect with nohup you could type nohup seq 1 10000000 > tee /tmp/file2. But the whole point of this exercise is to show you how to put something into the background incase you forgot to nohup it in the beginning. NOTE 3: you can specify which job to disown - otherwise disown -h without a job specifier will just put every job in the background. Type "jobs" to see all the jobs - note if you have alot of text flowing on the screen from a command you want to put in the background like in NOTE1 it will be near impossible to see the jobs output. Anyhow disown -h %n where n is the job number will but job n in the background. The job number is like the PID but not instead of the process it relates to the job number. Your job numbers will most likely be 1 or 2 or 3 etc., not like 1000 or 30000 which is what PIDs look like.  An example: seq 1 1000000000 > /tmp/file3 ctrl+z seq 1 1000000000 > /tmp/file4 ctrl+z jobs will show you that you have 2 jobs bg 1 disown -h %1 bg 2 disown -h %2 exit (method 3) PUT BACKGROUND PROCESS INTO NOHUP This is like method2, except lets say you put the process into the background but you want to nohup it. Why would you want to nohup it? Simple - Because you need close out the shell and you dont want your process to stop: Solution: jobs disown %n where n is the job number Example: # rsync -avz /source /destination & and its running in the background taking its sweet time to complete # jobs shows me its running with job number 1 # disown %1 now I can exit the shell with it still running safely (method 4) MANUAL PROCESS TO BACKGROUND (this is just like method1) Pro:  Same as first step but more Matrix Style - puts running process into backgroung with low level kernel signals Con:   If you quit out of the shell window the process stops Reference: http://stackoverflow.com/questions/625409/how-do-i-put-an-already-running-process-under-nohup If Ctrl-Z is not working Open another shell and: ps -aux (or) ps aux Then identify the PID of the process for example. And put that number in the PID field below. kill -20 PID  kill -18 PID kill -20 will suspend the process kill -18 will resume the process, in background. So now, closing both your terminals won't stop your process. Notes KILL SIGNALS BELOW - COMMON SIG COMMANDS Reference: http://linux.about.com/od/commands/l/blcmdl7_signal.htm SIGINT  2 Term Interrupt from keyboard SIGQUIT  3 Core Quit from keyboard SIGILL  4 Core Illegal Instruction SIGABRT  6 Core Abort signal from abort(3) SIGFPE  8 Core Floating point exception SIGKILL  9 Term Kill signal SIGSEGV 11 Core Invalid memory reference SIGPIPE 13 Term Broken pipe: write to pipe with no readers SIGALRM 14 Term Timer signal from alarm(2) SIGTERM 15 Term Termination signal SIGUSR1 30,10,16 Term User-defined signal 1 SIGUSR2 31,12,17 Term User-defined signal 2 SIGCHLD 20,17,18 Ign Child stopped or terminated SIGCONT 19,18,25 Continue if stopped SIGSTOP 17,19,23 Stop Stop process SIGTSTP 18,20,24 Stop Stop typed at tty SIGTTIN 21,21,26 Stop tty input for background process SIGTTOU 22,22,27 Stop tty output for background process ALTERNATE SOLUTION TO NOHUP AND BACKGROUND PROCESSES 1. dtach - this starts a bash/sh session in another process so if you exit out of your shell it still runs        Quick lesson on dtach         To start a new sesssion type the following (note it makes a socket file called dtach.session):  dtach -A /tmp/dtach.session /bin/bash          CONTROL+\ (key above enter key) = this gets you out of your dtach session and back in the shell you originally were in          You can now close out of your shell (putty, or xterm, etc.) and it will still run          To get back in your session dtach -A /tmp/dtach.session          To end the dtach session, either restart or get back in the session and then type cd / and then exit to close the session once and for all then remove the socket file  rm /tmp/dtach.session         NOTE1: It doesnt matter if you call it dtach.session, i could of just called it sally without the .dtach. the /bin/bash argument is needed but you can put another shell like  /bin/sh or even another program like rtorrent         2. screen - this is like dtach but with more "dtachs" you can even split the screen horizontaly and verticaly             Google it to find out how to use it - just google "how to install screen linux" and "screen linux cheatsheet" 3. byobu - this is like screen but with a cool looking bash screen border and everything and easier to use keys             Google it to find out how to use it - just google "how to install byobu" and "how to use byobu"