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- slow server because of security setup?
- Tom Forsmo
September 6, 2008, 8:57 am
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I have a server where I have done various security setup. The machine
has become quite slow now. The problem is that things hangs for some
time in the middle of operations, for no apparent reason. E.g. apt-get
update/upgrade stops several times in the middle of the operation and
hangs for 30-60 seconds before continuing. An SSH connection attempt
hangs up to 30 seconds before the login prompt appears. Sometimes it is
fast and sometimes its slow.
I attribute these problems to the security setup, since without the
security setup, the box was fast as could be expected, without any of
these hiccups. I mainly followed the Debian Security setup
documentation, not entirly, but the majort parts. So the I ran bastille
entirely and enabled its firewall. I turned off all services except ssh,
which I manually configured with basic setup, I configured the
hosts.allow/deny with basic deny all and allow ssh and a finger rule.
That is the major components of it.
What I am suspecting is that because bastille turned off things like the
possibility to send ping messages etc, it might also have turned on
something to rate adjust the speed of some services or network
functions. Alternatively, that bastille has configured the machine to
for example do reverse lookup/finger etc. of the connecting machine.
This, then, does not work because of the connecting machines own
security setup, so the process hangs until the network timeout occurs.
Something similar might be the cause with apt-get.
Any ideas what the problem might be and how to fix it?
Re: slow server because of security setup?
Complete guess, but I'd go for a problem with your DNS. Starting an ssh
session will do both a forward and a reverse lookup, and either of those
failing will cause the session to hang for quite a while.
It's unlikely to be your security setup, as if you were being blocked it
would hang indefinitely and not resume after a few seconds.
I'd start with the networking basics and go from there.
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