SSH problems - server unexpectedly closed network connection

Question

Since yesterday I have problems connecting to my server using SSH/SFTP. I can only connect after a restart of my server. When I try to make a connection after a couple of minutes, I can no longer make an SSH connection. I get the error "server unexpectedly closed network connection". SSH connections that are already open stay open. My server has CentOS 6 on it.

Furthermore varnish keeps crashing seemingly randomly, which means my sites get down.

In my SSH error log I get the error:

fatal: setresuid 500: Resource temporarily unavailable
pam_unix(sshd:session): session closed for user

Any ideas what the problem may be? Thanks

Solution

The documentation of the setresuid system call has this explanation:

ERRORS
       EAGAIN uid  does  not  match  the current UID and this call would bring
              that user ID over its RLIMIT_NPROC resource limit.

In other words you are trying to login as a user, who already has the maximum of allowed processes. Login as another user should still work and allow you to find out what processes are running as the first user.

Comments

[MadHatter]

My guess would be that this is a virtual server, and it's running out of memory. Without quite a lot more information, it's hard to tell.

[Jenny D]

Did you look in any of the server logs?

[user219682]

Not a virtual server. 32Gb of memory and I'm not running out of memory. I am no going to do a complete hardware swap, except for the hard drive. Hope that helps. Server logs weren't very helpful, only thing I could see that varnish was crashing.