Need Help Diagnosing Server Wierdness

[Lisa Kachold]

Hello Mark,




On Sat, May 25, 2013 at 11:59 AM, Mark Phillips
<mark at phillipsmarketing.biz>wrote:

> I have an old headless server running Linux version 2.6.32-5-686 (Debian
> 2.6.32-48squeeze1) (dannf at debian.org) (gcc version 4.3.5 (Debian 4.3.5-4)
> ). Recently, when I log in using ssh the terminal window freezes for a few
> seconds, then usually comes back. The command line stops printing the
> characters I am typing, the cursor stops blinking, and then after a few
> seconds, it comes back. This happens every few minutes, so it is becoming
> rather annoying.
>

Here's the general list (some of which you have done already).

0 - Make sure that it's not swapping with "free".
1 - Check that you have no ethernet errors with "ethtool eth0" (or whatever
your interfaces are) and look for errors.
1.5 - Check  ' netstat -s -p|grep "segments retransmited" ' for packet loss
2 - Check "netstat -antp" to see what is listening and/or bogging down.
3 - Check "lsof" to see what the system is doing.
4 - Are you accessing SSH via SSH forwarding, a different place/network or
VPN?  This could be a MTU issue.
5 - Run "nmap $servername" from your system to check what is available and
listening.
6 - Look in your logs for security issues; specifically access attempts to
open ports; firewall to only allow source and destination for SSH, DNS or
other Mail as appropriate.
7 - Disable your SSH timeout - just to be safe:
http://docs.oseems.com/general/application/ssh/disable-timeout
8 - Use a ping from your system to the server to see if you can see latency.
9 - Use a traceroute/tracert to see latency between any hop.


Use the Source my friend!

>
> When I check the disks, I get
> # df -h
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sda1             182G   42G  131G  25% /
> tmpfs                 505M     0  505M   0% /lib/init/rw
> udev                  500M  140K  500M   1% /dev
> tmpfs                 505M     0  505M   0% /dev/shm
> /dev/sdb1             230G  146G   72G  67% /mnt/sdb
>
> So I am not running out of disk space.
>
> When I run top, I get this output:
> Tasks:  90 total,   3 running,  87 sleeping,   0 stopped,   0 zombie
> Cpu(s):  7.0%us,  3.0%sy,  0.0%ni, 82.7%id,  6.6%wa,  0.3%hi,  0.3%si,
> 0.0%st
> Mem:   1032748k total,  1013748k used,    19000k free,   242992k buffers
> Swap:  2017272k total,     1040k used,  2016232k free,   473584k cached
>
> So I am not running a process that is taking over the CPU.
>
> How should I go about diagnosing this problem?
>
> Thanks!
>
> Mark
>
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