Linux become slow to authenticate ?

[bluegroper]

I run a small office Linux server. Pentium 200 with 128Mb Ram and 40Gb HDD. RH7.3, Samba, dhcp, email server.
Today the server has started behaving strangely. It is suddenly running quite "slowly". I have done no upgrades, nor changed any settings, or fiddled with anything that I think might cause this.
Samba seems to be working just fine, as it always does.
But when users check their email, it now takes about 20 secs instead of the usual <1 sec.
When I login using telnet (ssh), it takes about 15 seconds to authenticate me instead of the usual <1 sec.
top tells me that the system is only using about 75% of RAM, and none of the swapfile is being used.
hdparm -t /dev/hda gives me about 22 MB/sec which is normal.
I've started to look in the logs, and all I can find in /var/log/secure is confirmation that every email check is taking over 20 secs.
Yes, I've rebooted the server. Didn't expect that to help, but WindoZe has taught me that you do it anyway.
Anybody got any suggestions as to where else I should start looking for the cause of this partial slowness ?
Yes I would RTFM if I could find the right page to look at !
TIA's

 

[pupu]

This kind of problem is usually connected with DNS. Check your /etc/resolv.conf and probe listed servers manually (dig, nslookup...)

 

[tarn]

I can only re-iterate what pupu has said, this is usually caused when the server tries to do a forward lookup for your connection, it eventually times out and allows you to connect but there can be some prolonged delay.

Yes confirm that your DNS server is available (and more the point that you have it correctly defined in /etc/resolv.conf) and while you’re there be sure that the other setting &quot;files, dns&quot; is set correctly in /etc/nsswitch.conf .... These can both usually get missed when setting up a server.

Good Luck,
Laurie