Blog

Netconsole

Ever tried setting up netconsole under Linux, but never received anything from the kernel log on the machine configured as target in the netconsole module?

Check the kernel.printk setting in sysctl. For me, the following values seem to fix netconsole:
kernel.printk = 7 4 1 7

Tags: 

Topics: 

Why nobody should use the uceprotect DNSBL

Geez...

Today one of the mail servers I'm maintaining seems to be blacklisted in the uceprotect blacklist. I had never heard of them until now. And I must say, the guys at uceprotect really think they are the Gods of mail or something.

If you want to get yourself removed from this list, you either have to wait 7 days - given that your server's IP address doesn't connect to their trap again. Or, you could pay these sons of bitches 50€ (per IP!!!) to get unlisted immediately. This is totally unacceptable, who the hell do they think they are???

In addition to this complete non-sense, they mention on their page how you can find the reason for being blacklisted in your mail logs:


Grep the logs (last 8 days) on your server for following expression:

Topics: 

Dell + booting from USB devices

Recently I needed to boot a Dell server (PE1950) from a USB flash drive. The flash drive contained a bootable image from the CentOS 5 DVD (images/diskboot.img), to run the CentOS installer, and kickstart the machine over the network.

When cold booting these machines (eg. from a power down state), there is no problem at all.

Syslog-NG: Number of allowed concurrent connections exceeded

When I moved from syslog to syslog-ng on my laptop running Fedora 7, I noticed a lot of these warnings in /var/log/messages:


Jul 10 09:29:34 speedy syslog-ng[2272]: Number of allowed concurrent connections exceeded; num='10', max='10'

Increasing the maximum number of connections for the Unix stream that reads /dev/log seemed to fixed this problem:

Tags: 

Topics: 

Changing the maximum number of open file descriptors

On Linux, there is a global and per-user limit of open file descriptors (read: maximum number of open files). The global limit is distribution and kernel specific, the per-user limit is set to 1024 by default. However, some applications, like Lotus Domino, Oracle, ... require to have more than 1024 open files.

Global limit

The current global limit can be checked with:
cat /proc/sys/fs/file-max

To change the global limit, you can do:
echo 65536 > /proc/sys/fs/file-max

Unfortunately, if you set the limit with the above command, it will not be saved after a reboot. To change this parameter at every boot, you have to add this to /etc/sysctl.conf:
fs.file-max = 65536

Tags: 

Topics: 

Pages

Subscribe to RSS - blogs