How do I put an already-running process under nohup

Question

I have a process that is already running for a long time and don t want to end it   How do I put it under nohup  that is  how do I cause it to continue running even if I close the terminal

User · Accepted Answer

Using the Job Control of bash to send the process into the background    Ctrl Z to stop  pause  the program and get back to the shell  bg to run it in the background  disown -h  job-spec  where  job-spec  is the job number  like  1 for the first running job  find about your number with the jobs command  so that the job isn t killed when the terminal closes

User · Answer

On my AIX system  I tried   nohup -p  processid gt    This worked well  It continued to run my process even after closing terminal windows  We have ksh as default shell so the bg and disown commands didn t work

User · Answer

To send running process to nohup  http   en wikipedia org wiki Nohup   nohup -p pid   it did not worked for me  Then I tried the following commands and it worked very fine   Run some SOMECOMMAND   say  usr bin python  vol scripts python scripts retention all properties py 1  Ctrl Z to stop  pause  the program and get back to the shell  bg to run it in the background  disown -h so that the process isn t killed when the terminal closes  Type exit to get out of the shell because now you re good to go as the operation will run in the background in its own process  so it s not tied to a shell    This process is the equivalent of running nohup SOMECOMMAND

User · Answer

Simple and easiest steps  Ctrl   Z ---------- gt  Suspends the process bg       -------------- gt  Resumes and runs background disown  1 ------------- gt  required only if you need to detach from the terminal

User · Answer

ctrl   z  - this will pause the job  not going to cancel   bg - this will put the job in background and return in running process disown -a - this will cut all the attachment with job  so you can close the terminal and it will still run    These simple steps will allow you to close the terminal while keeping process running   It wont put on nohup  based on my understanding of your question  you don t need it here

User · Answer

These are good answers above  I just wanted to add a clarification   You can t disown a pid or process  you disown a job  and that is an important distinction   A job is something that is a notion of a process that is attached to a shell  therefore you have to throw the job into the background  not suspend it  and then disown it   Issue      jobs  1   running java   2   suspended vi    disown  1   See http   www quantprinciple com invest index php docs tipsandtricks unix jobcontrol  for a more detailed discussion of Unix Job Control

User · Answer

The command to separate a running job from the shell     makes it nohup  is disown and a basic shell-command   From bash-manpage  man bash       disown  -ar   -h   jobspec           Without options  each jobspec is removed from the table of active jobs  If the -h option is given  each jobspec is not   removed from the table  but is marked so that SIGHUP is not sent to the job if the shell receives a SIGHUP  If no jobspec is   present  and neither the -a nor the -r option is supplied  the current job is used  If no jobspec is supplied  the -a option   means to remove or mark all jobs  the -r option without a jobspec argument restricts operation to running jobs  The return   value is 0 unless a jobspec does not specify a valid job    That means  that a simple  disown -a   will remove all jobs from the job-table and makes them nohup

User · Answer

Node s answer is really great  but it left open the question how can get stdout and stderr redirected  I found a solution on Unix  amp  Linux  but it is also not complete  I would like to merge these two solutions  Here it is   For my test I made a small bash script called loop sh  which prints the pid of itself with a minute sleep in an infinite loop      loop sh   Now get the PID of this process somehow  Usually ps -C loop sh is good enough  but it is printed in my case   Now we can switch to another terminal  or press  Z and in the same terminal   Now gdb should be attached to this process     gdb -p  lt PID gt    This stops the script  if running   Its state can be checked by ps -f  lt PID gt   where the STAT field is  T    or in case of  Z  T    which means  man ps 1        T Stopped  either by a job control signal or because it is being traced       is in the foreground process group   gdb  call close 1   1   0   Close 1  returns zero on success    gdb  call open  loop out   01102  0600   6   1   Open 1  returns the new file descriptor if successful   This open is equal with open path  O TRUNC O CREAT O RDWR  S IRUSR S IWUSR    Instead of O RDWR O WRONLY could be applied  but  usr sbin lsof says  u  for all std  file handlers  FD column   which is O RDWR   I checked the values in  usr include bits fcntl h header file   The output file could be opened with O APPEND  as nohup would do  but this is not suggested by man open 2   because of possible NFS problems   If we get -1 as a return value  then call perror     prints the error message  If we need the errno  use p errno gdb comand   Now we can check the newly redirected file   usr sbin lsof -p  lt PID gt  prints   loop sh  lt PID gt  truey    1u   REG   0 26        0 15008411  home truey loop out   If we want  we can redirect stderr to another file  if we want to using call close 2  and call open      again using a different file name   Now the attached bash has to be released and we can quit gdb    gdb  detach Detaching from program   bin bash  process  lt PID gt   gdb  q   If the script was stopped by gdb from an other terminal it continues to run  We can switch back to loop sh s terminal  Now it does not write anything to the screen  but running and writing into the file  We have to put it into the background  So press  Z     Z  1    Stopped                   loop sh    Now we are in the same state as if  Z was pressed at the beginning    Now we can check the state of the job     ps -f 24522 UID        PID  PPID  C STIME TTY      STAT   TIME CMD  lt UID gt      lt PID gt  lt PPID gt   0 11 16 pts 36   S      0 00  bin bash   loop sh   jobs  1    Stopped                   loop sh   So process should be running in the background and detached from the terminal  The number in the jobs command s output in square brackets identifies the job inside bash  We can use in the following built in bash commands applying a     sign before the job number      bg  1  1     loop sh  amp    disown -h  1   ps -f  lt PID gt  UID        PID  PPID  C STIME TTY      STAT   TIME CMD  lt UID gt      lt PID gt  lt PPID gt   0 11 16 pts 36   S      0 00  bin bash   loop sh   And now we can quit from the calling bash  The process continues running in the background  If we quit its PPID become 1  init 1  process  and the control terminal become unknown     ps -f  lt PID gt  UID        PID  PPID  C STIME TTY      STAT   TIME CMD  lt UID gt      lt PID gt      1  0 11 16          S      0 00  bin bash   loop sh    usr bin lsof -p  lt PID gt      loop sh  lt PID gt  truey    0u   CHR 136 36                38  dev pts 36  deleted  loop sh  lt PID gt  truey    1u   REG   0 26     1127 15008411  home truey loop out loop sh  lt PID gt  truey    2u   CHR 136 36                38  dev pts 36  deleted    COMMENT  The gdb stuff can be automatized creating a file  e g  loop gdb  containing the commands and run gdb -q -x loop gdb -p  lt PID gt   My loop gdb looks like this   call close 1  call open  loop out   01102  0600    call close 2    call open  loop err   01102  0600  detach quit   Or one can use the following one liner instead   gdb -q -ex  call close 1   -ex  call open  loop out   01102  0600   -ex detach -ex quit -p  lt PID gt    I hope this is a fairly complete description of the solution

User · Answer

Suppose for some reason Ctrl Z is also not working  go to another terminal  find the process id  using ps  and run   kill -SIGSTOP PID  kill -SIGCONT PID   SIGSTOP will suspend the process and SIGCONT will resume the process  in background  So now  closing both your terminals won t stop your process

User · Answer

Unfortunately disown is specific to bash and not available in all shells   Certain flavours of Unix  e g  AIX and Solaris  have an option on the nohup command itself which can be applied to a running process   nohup -p pid   See http   en wikipedia org wiki Nohup

User · Answer

This worked for me on Ubuntu linux while in tcshell    CtrlZ to pause it bg to run in background jobs to get its job number nohup  n where n is the job number

[shell] How do I put an already-running process under nohup?

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