Linux – Set max file limit on a running process

If you're using Bash, you can run disown -h job

disown

disown [-ar] [-h] [jobspec ...]

Without options, each jobspec is removed from the table of active jobs. If the -h option is given, the job 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 jobspec is not present, and neither the -a nor -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.

file-max is the maximum File Descriptors (FD) enforced on a kernel level, which cannot be surpassed by all processes without increasing. The ulimit is enforced on a process level, which can be less than the file-max.

There is no performance impact risk by increasing file-max. Modern distributions have the maximum FD set pretty high, whereas in the past it required kernel recompilation and modification to increase past 1024. I wouldn't increase system-wide unless you have a technical need.

The per-process configuration often needs tuned for serving a particular daemon be it either a database or a Web server. If you remove the limit entirely, that daemon could potentially exhaust all available system resources; meaning you would be unable to fix the problem except by pressing the reset button or power cycling. Of course, either of those is likely to result in corruption of any open files.