In /var/log/auth.log
appears too many messages Removed session
Jun 2 17:42:39 srv-1 systemd-logind[13785]: Removed session c36006.
Jun 2 17:42:39 srv-1 systemd-logind[13785]: Removed session c36007.
Jun 2 17:42:40 srv-1 systemd-logind[13785]: Removed session c36008.
Jun 2 17:42:41 srv-1 systemd-logind[13785]: Removed session c36009.
Jun 2 17:42:41 srv-1 systemd-logind[13785]: Removed session c36010.
Jun 2 17:42:41 srv-1 systemd-logind[13785]: Removed session c36011.
Jun 2 17:42:42 srv-1 systemd-logind[13785]: Removed session c36012.
Jun 2 17:42:43 srv-1 systemd-logind[13785]: Removed session c36013.
Jun 2 17:42:43 srv-1 systemd-logind[13785]: Removed session c36014.
Jun 2 17:42:43 srv-1 systemd-logind[13785]: Removed session c36015.
Jun 2 17:42:44 srv-1 systemd-logind[13785]: Removed session c36016.
Jun 2 17:42:45 srv-1 systemd-logind[13785]: Removed session c36017.
Jun 2 17:42:45 srv-1 systemd-logind[13785]: Removed session c36018.
Jun 2 17:42:46 srv-1 systemd-logind[13785]: Removed session c36019.
Jun 2 17:42:47 srv-1 systemd-logind[13785]: Removed session c36020.
Jun 2 17:42:48 srv-1 systemd-logind[13785]: Removed session c36021.
and no message about New session, i can't understand what causing this problem
uname -a
Linux backup-01 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.4 LTS
Release: 14.04
Codename: trusty