How to set ulimit values

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 5
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7

Issue

  • How to set ulimit values

Resolution

  • Settings in /etc/security/limits.conf take the following form:

    # vi /etc/security/limits.conf
    #<domain>        <type>  <item>  <value>
    
    *               -       core             <value>
    *               -       data             <value>
    *               -       priority         <value>
    *               -       fsize            <value>
    *               soft    sigpending       <value> eg:57344
    *               hard    sigpending       <value> eg:57444
    *               -       memlock          <value>
    *               -       nofile           <value> eg:1024
    *               -       msgqueue         <value> eg:819200
    *               -       locks            <value>
    *               soft    core             <value>
    *               hard    nofile           <value>
    @<group>        hard    nproc            <value>
    <user>          soft    nproc            <value>
    %<group>        hard    nproc            <value>
    <user>          hard    nproc            <value>
    @<group>        -       maxlogins        <value>
    <user>          hard    cpu              <value>
    <user>          soft    cpu              <value>
    <user>          hard    locks            <value>
    
    • <domain> can be:

      • an user name
      • a group name, with @group syntax
      • the wildcard *, for default entry
      • the wildcard %, can be also used with %group syntax, for maxlogin limit
    • <type> can have the two values:

      • "soft" for enforcing the soft limits
      • "hard" for enforcing hard limits
    • <item> can be one of the following:

      • core - limits the core file size (KB)
      • data - max data size (KB)
      • fsize - maximum filesize (KB)
      • memlock - max locked-in-memory address space (KB)
      • nofile - max number of open files
      • rss - max resident set size (KB)
      • stack - max stack size (KB)
      • cpu - max CPU time (MIN)
      • nproc - max number of processes
      • as - address space limit (KB)
      • maxlogins - max number of logins for this user
      • maxsyslogins - max number of logins on the system
      • priority - the priority to run user process with
      • locks - max number of file locks the user can hold
      • sigpending - max number of pending signals
      • msgqueue - max memory used by POSIX message queues (bytes)
      • nice - max nice priority allowed to raise to values: [-20, 19]
      • rtprio - max realtime priority
  • Exit and re-login from the terminal for the change to take effect.

  • More details can be found from below command:

# man limits.conf

Diagnostic Steps

  • To improve performance, we can safely set the limit of processes for the super-user root to be unlimited. Edit the .bashrc file vi /root/.bashrc and add the following line:
# vi /root/.bashrc
ulimit -u unlimited
  • Exit and re-login from the terminal for the change to take effect.
  • Can also run ulimit -u unlimited at the command prompt instead of adding it to the /root/.bashrc file.

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