[Bug 1561658] Re: ssh sessions don't run in session cgroup but in sshd's -- pam_systemd missing

[Gustavo Romero]

Hi, Martin. It seems Breno talked to Adam Conrad and the pcc64le ISO is
not installing policykit-1 (but it should as we can see here
http://goo.gl/WTK54h) correctly. The ISO I installed and tested is this
one here:

http://cdimage.ubuntu.com/ubuntu-server/daily/current/xenial-server-
ppc64el.iso

Regarding getting libpam-systemd higher on the install stack or not, I
think (but not sure) the install procedure doesn't install by default
"Recommends", so it won't install libpam-systemd anyway if policykit-1
is removed from install. On x64 we get libpam-systemd only because of
polocykit-1 being installed, and given the importance of libpam-systemd
I would vote for b) as Breno said, ie not "Recommends", but "Depends".

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Title:
  ssh sessions don't run in session cgroup but in sshd's -- pam_systemd
  missing

Status in systemd package in Ubuntu:
  Incomplete

Bug description:
  On Ubuntu 16.04/ppc64el, the cgroup for a user session (bash) inherits
  from a sshd.service, when the user logs into the machine using SSH.

  This causes the amount of process to be limited by
  /etc/systemd/system/conf DefaultTasksMax=512

  This does not seem to happen on amd64. This is a cgroup tree diff:

  On x64, bash (in this case, PID 19405 ) spawned by sshd belongs to CGROUP session-5.scope->user-1003.slice->user.slice: 
   
  └─user.slice
    ├─user-1000.slice
    │ ├─session-1.scope
    │ │ ├─634 sshd: brenohl [priv]
    │ │ ├─660 sshd: brenohl at pts/0 
    │ │ └─661 -bash
    │ └─user at 1000.service
    │   ├─636 /lib/systemd/systemd --user
    │   └─637 (sd-pam)  
    └─user-1003.slice
      ├─session-5.scope
      │ ├─19379 sshd: gromero [priv]
      │ ├─19404 sshd: gromero at pts/1 
      │ ├─19405 -bash

  However, in ppc64le, bash (in this case, PID 1913), spawned by sshd
  belongs to CGROUP ssh.service->system.slice->-.slice:

  -.slice
  ├─1720 /sbin/cgmanager -m name=systemd
  ├─init.scope
  └─system.slice
    ├─dbus.service
    │ └─1699 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
    ├─cron.service
    │ └─1702 /usr/sbin/cron -f
    ├─ifup at eth0.service
    │ └─1833 /sbin/dhclient 
    ├─accounts-daemon.service
    │ └─1717 /usr/lib/accountsservice/accounts-daemon
    ├─system-serial\x2dgetty.slice
    │ └─serial-getty at hvc0.service
    │   └─1875 /sbin/agetty --keep-baud 115200 38400 9600 hvc0 vt220
    ├─systemd-journald.service
    │ └─1382 /lib/systemd/systemd-journald
    ├─systemd-timesyncd.service
    │ └─1639 /lib/systemd/systemd-timesyncd
    ├─ssh.service
    │ ├─1863 /usr/sbin/sshd -D
    │ ├─1897 sshd: gromero [priv]
    │ ├─1912 sshd: gromero at pts/0 
    │ ├─1913 -bash

  
  Having the user session associated with the systemd cgroups (/system.slice/ssh.service) instead of normal user/session cgroups (as user-XXXX.slice/session-5.scope), causes the process to be limited to the systemd TasksMax limit, thus, causing "Cannot fork" and "Resource temporary unavailable" problems when the amount of processes reaches this 512 limit.

  Gustavo Romero has more details about this problem, and will comment
  soon.

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