[Bug 1772315] [NEW] ulimit can be enlarged, but not reduced back to below original

[Roel Van de Paar]

Public bug reported:

Last login: Sat May 19 15:50:25 2018 from 192.168.0.130
~$ ulimit -u 5000
~$ ulimit -u 1000
~$ ulimit -u 10000
-bash: ulimit: max user processes: cannot modify limit: Operation not permitted
~$ ulimit -u 8000
-bash: ulimit: max user processes: cannot modify limit: Operation not permitted
~$ ulimit -u 7000
-bash: ulimit: max user processes: cannot modify limit: Operation not permitted
~$ ulimit -u 6000
-bash: ulimit: max user processes: cannot modify limit: Operation not permitted
~$ ulimit -u 5000
-bash: ulimit: max user processes: cannot modify limit: Operation not permitted
~$ ulimit -u 4000
-bash: ulimit: max user processes: cannot modify limit: Operation not permitted

~$ cat /etc/security/limits.conf  | grep nproc | grep -v "^#"
* soft nproc 20480
* hard nproc 20480

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: bash 4.4.18-2ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
Date: Mon May 21 07:12:11 2018
InstallationDate: Installed on 2018-04-06 (44 days ago)
InstallationMedia: Ubuntu-Server 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180402)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: bash
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: bash (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug bionic

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https://bugs.launchpad.net/bugs/1772315

Title:
  ulimit can be enlarged, but not reduced back to below original

Status in bash package in Ubuntu:
  New

Bug description:
  Last login: Sat May 19 15:50:25 2018 from 192.168.0.130
  ~$ ulimit -u 5000
  ~$ ulimit -u 1000
  ~$ ulimit -u 10000
  -bash: ulimit: max user processes: cannot modify limit: Operation not permitted
  ~$ ulimit -u 8000
  -bash: ulimit: max user processes: cannot modify limit: Operation not permitted
  ~$ ulimit -u 7000
  -bash: ulimit: max user processes: cannot modify limit: Operation not permitted
  ~$ ulimit -u 6000
  -bash: ulimit: max user processes: cannot modify limit: Operation not permitted
  ~$ ulimit -u 5000
  -bash: ulimit: max user processes: cannot modify limit: Operation not permitted
  ~$ ulimit -u 4000
  -bash: ulimit: max user processes: cannot modify limit: Operation not permitted

  ~$ cat /etc/security/limits.conf  | grep nproc | grep -v "^#"
  * soft nproc 20480
  * hard nproc 20480

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: bash 4.4.18-2ubuntu1
  ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
  Uname: Linux 4.15.0-20-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7
  Architecture: amd64
  Date: Mon May 21 07:12:11 2018
  InstallationDate: Installed on 2018-04-06 (44 days ago)
  InstallationMedia: Ubuntu-Server 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180402)
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=C.UTF-8
   SHELL=/bin/bash
  SourcePackage: bash
  UpgradeStatus: No upgrade log present (probably fresh install)

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