I noticed following behavior on two of my CENTOS7 machines .. (it also happened on a RHEL6 too).
Sometimes meanwhile i'm typing, my session freezes. What I've already figured out.
- Router shows connections as still active but as idle
- ping has recorded no errors while transmitting packets (server got pinged the whole login)
- I can immediately login to a second session, check the log and see following:
systemd-logind: New session 1 of user root. systemd: Started Session 1 of user root. systemd: Starting Session 1 of user root. systemd-logind: New session 2 of user root. systemd: Started Session 2 of user root. systemd: Starting Session 2 of user root.
So the session, seems to be opened anyway. As soon as I close the freezed window systemd-logind: Removed session 1.
appears.
There is no error "Write failed: Broken pipe", which appears after a disconnect.
I connect via BASH from my ubuntu desktop. It never happended to another Server. Just them. SSH is configured with default settings.
The machine is setted up new, it is a cluster and it appers on both nodes. Well actually the cluster isn't configured, they are just two server, setted up completey the same.
EDIT: I also noticed, that the freezed session is shown as active on the router, but idle since freeze, even with the session window closed ..
watch
andnetstat -s
to keep an eye on counters that may prove usefull here. Just source that function and typewatch_net
, ideally in a screen session.net.ipv4.tcp_thin_linear_timeouts=1
andnet.ipv4.tcp_thin_dupack = 1
in /etc/sysctl.conf and runsysctl -e -p
after you research what that does and if your kernel supports it.