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From https://stackoverflow.com/a/17483998/156458

while you do need to be root to raise the limit to 65535, you probably don’t want to run your program as root. So after you raise the limit you should switch back to the current user.

To do this, run:

sudo sh -c "ulimit -n 65535 && exec su $LOGNAME"

From Why does the following way not change core file limit size?, I would like to do the following:

I should put the command which uses the new limit value inside the shell executed by sudo

e.g.

$ sudo sh -c "ulimit -c 1024 && sleep 100"
^\Quit
$ ls
core

ulimit -c 1024 needs super user privilleges, while sleep 100 doesn't.

How can I change my command so that sleep 100 doesn't run with superuser privilleges but with the changed limit value?

Update:

I tried the command from the replay by Hauke, and suspected the reason of its failure is because sudo -c doesn't work on Linux, and still wonder what his intention of using sudo -c was:

$ sudo sh -c "ulimit -c 1024 && sudo -u nobody -c \"sleep 100\""
[sudo] password for t: 
usage: sudo -h | -K | -k | -V
usage: sudo -v [-AknS] [-g group] [-h host] [-p prompt] [-u user]
usage: sudo -l [-AknS] [-g group] [-h host] [-p prompt] [-U user] [-u user] [command]
usage: sudo [-AbEHknPS] [-r role] [-t type] [-C num] [-g group] [-h host] [-p prompt] [-T timeout] [-u user] [VAR=value] [-i|-s] [<command>]
usage: sudo -e [-AknS] [-r role] [-t type] [-C num] [-g group] [-h host] [-p prompt] [-T timeout] [-u user] file ...

I have tried the following two commands, but the whole commands return immediately instead of running sleep 100. Why?

$ sudo bash -c "ulimit -c 1024  && exec su $LOGNAME && sleep 100"
$ sudo bash -c "ulimit -c 1024  && exec bash -c \"su $LOGNAME;  sleep 100\" "
$

The following command creates a core file. But does the second sudo not clear up the limits by default? I heard sudo often or always clean up execution environment?

$ ulimit -c
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$ sudo sh -c "ulimit -c 1024 && sudo -u nobody sleep 100"

I found http://jdebp.eu./Softwares/nosh/guide/ulimit.html from https://unix.stackexchange.com/a/446619/674, and wonder how I could achieve similar things using shell scripts:

Most shells have a built-in ulimit command that does not chain and that has additional interactive functionality. See the manual for each individual shell for its built-in command. This command is more commonly used with exec(1) and nosh(1).

Thanks.

Tim
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  • "I have tried the following two commands, but the whole commands return immediately" ... no, it doesn't. https://unix.stackexchange.com/questions/70859/why-doesnt-sudo-su-in-a-shell-script-run-the-rest-of-the-script-as-root – muru May 31 '18 at 04:17
  • Not that you probably care anymore, but exec command has command replace the shell instance. Thus, when it exits, so does the shell instance. Any subsequent commands therefore have nowhere to run, as it were, and they are just dropped. For example, running (exec echo "hello" && echo 1 > /tmp/exec_test) -- note the parentheses -- does not create the file /tmp/exec_test. Run man builtins to read more about exec. – Zorawar Oct 19 '20 at 16:07

1 Answers1

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sudo sh -c "ulimit -c 1024 && sudo -u nobody -c \"sleep 100\""
Hauke Laging
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  • Thanks. I added some commands at the end which I have tried. I was wondering why sleep 100 doesn't run in both commands? – Tim May 28 '18 at 20:21
  • But nobody is somebody. It has access to all resources (files, processes etc) owned by nobody. – ctrl-alt-delor May 28 '18 at 20:26
  • In your command, (1) does the second sudo not clear up the limits by default? I heard sudo always clean up execution environment. (2) Do you use -c to the second sudo for specifying the command to run? I found it doesn't work, instead sudo sh -c "ulimit -c 1024 && sudo -u nobody sleep 100" works. – Tim May 28 '18 at 20:27
  • @ctrl-alt-delor How is that relevant? The question is about "without superuser privilleges". – Hauke Laging May 29 '18 at 09:06
  • Hauke, if you have a chance, I have updated my post. – Tim May 29 '18 at 12:27