[Bug 1794169] Missing required logs.

[Ubuntu Kernel Bot]

This bug is missing log files that will aid in diagnosing the problem.
While running an Ubuntu kernel (not a mainline or third-party kernel)
please enter the following command in a terminal window:

apport-collect 1794169

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
to run this command, please add a comment stating that fact and change
the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

** Changed in: linux (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1794169

Title:
  AWS ubuntu became unreachable after ssh login

Status in linux package in Ubuntu:
  Incomplete
Status in systemd package in Ubuntu:
  New

Bug description:
  I've reached strange situation with Ubuntu 18.04 LTS with latest
  kernel on AWS m5.xlarge instance.

  System became unreachable after series of successful ssh logins.
  systemd -user became zombie and block main systemd daemon (PID 1).

  I've created bug https://github.com/systemd/systemd/issues/10123 but
  it was closed with "there's a problem with your kernel".
  https://github.com/systemd/systemd/issues/10123#issuecomment-423984751

  Symptoms are very similar to
  https://github.com/systemd/systemd/issues/8598

  apetren+ 26679  0.0  0.0      0     0 ?        Z    02:56   0:00  \_ [(sd-pam)] <defunct>
  apetren+ 26855  0.0  0.0  76636  7816 ?        Ds   02:57   0:00 /lib/systemd/systemd --user
  apetren+ 26856  0.0  0.0      0     0 ?        Z    02:57   0:00  \_ [(sd-pam)] <defunct>
  apetren+ 26954  0.0  0.0      0     0 ?        Zs   02:57   0:00  \_ [kill] <defunct>
  apetren+ 27053  0.0  0.0  76636  7496 ?        Ss   02:58   0:00 /lib/systemd/systemd --user
  apetren+ 27054  0.0  0.0 193972  2768 ?        S    02:58   0:00  \_ (sd-pam)

  This situation is repeatable on 7 instances 1-2 times per week.

  how to repeat: 1. Install ubuntu 18.04 LTS from official ubuntu image
  2. update kernel and packages to latest version 3. from another
  instance run

  while `true` ;do ssh ubuntu at your.instance.ip "hostname; ps -ef|grep
  defunc |grep -v grep" ; done

  By this command in couple of days I have 2->4->6->8... zombies and in
  a hour system is frozen...

  sudo reboot is not working, because systemd with PID 1 is unreachable.
  kill -9 1 -- not working as well.

  # uname -r:
  Linux mainframe04 4.15.0-1021-aws #21-Ubuntu SMP Tue Aug 28 10:23:07 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

  # cat /etc/lsb-release
  DISTRIB_ID=Ubuntu
  DISTRIB_RELEASE=18.04
  DISTRIB_CODENAME=bionic
  DISTRIB_DESCRIPTION="Ubuntu 18.04.1 LTS"

  # systemd --version
  systemd 237
  +PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD -IDN2 +IDN -PCRE2 default-hierarchy=hybrid

  
  AWS instance m5.xlarge

  Please let me know if you need any information.

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