Many commands seem to hang Ubuntu Server

We have an installation of Ubuntu Server (running 16.04.4 LTS) that, at some point in the last week or so, started having problems. Just about every command I try to run seems to completely hang the terminal. CTRL + C doesn't work, nor do some of the other key commands I've seen suggested (e.g. CTRL + D, Z, backslash)

• ps seems to work, but ps aux hangs
• top hangs
• doing an ls in certain folders causes the terminal to hang

Here is what I've tried:

• All packages are up-to-date.
• I don't see anything unusual in /var/log/syslog.
• Rebooting the server doesn't help.
• badblocks revealed no errors.
• I tried dmesg, but it seems to hang as well.
• Running some of the hanging commands with strace produces some output, but it hangs as well and I'm too much of a Linux noob to really make much of the output anyway. I'm happy to paste some in if it will help, though.

I have no NFS shares mounted. The server is used for application logging and is only running Elasticsearch/Kibana (behind nginx). Elasticsearch itself seems to be working fine (documents sent to it are being indexed).

1 Answer

I think I've discovered the culprit, and it has nothing to do with the VM itself. I think our network/firewall settings changed recently and it was interfering with SSH traffic. I connected to the VM with a different internet connection (outside our corporate network) and was able to administer the machine over SSH with no issues.

I'll leave this as the accepted answer in the event that someone else comes along with random weird SSH hangs and it is helpful, but mods should feel free to close this question if it is too narrow.