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

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?)

Solution 1:

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.

Solution 2:

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.

Solution 3:

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

Solution 4:

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.

Solution 5:

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