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Showing posts from February, 2008

Logical Volume Manager Cheatsheet

A little petpeev of mine just got solved, I think, thanks to the Logical Volume Manager Cheatsheet by Martin Ankerl.

One thing I was still doing in X11 (i.e. runlevel 5) was adding, creating and adjusting LVM disks. The GUI just makes things sooo much easier. Thanks to Martin's cheatsheet, though, I think I can easily add new LUNs to existing Volume Groups and extend my Logical Volumes... Cheers Martin!

Linux installation kickstart for Oracle database

A semi-random Google browse landed me on the Official Oracle Wiki, where I found a Linux installation kickstart for Oracle database. It's a sample kickstart file for a local disk installation using the minimum packages needed by Oracle software (i.e. the database, application server, etc.). The script also sets runlevels for daemon and deinstalls all that is not needed, as well as kernel parameters.

It's interesting to see their list because I highly optimizes the packages list compared to what we have. But the list of parameters, default daemons to run and in which runlevel is very close to what we arrived at by experimenting lots. :)

cURL - Vulernability Table

Someone alerted me to a possible security risk because of cURL. So I checked the cURL - Vulernability Table and found they are in some part right. cURL, libcurl, has a set of known vulnerabilities that are fixed but our Oracle Linux release does not (yet) use the most stable version released. Instead, it uses the version Oracle has included based on Red Hat's sources.

So we may need to do an update across our servers. Especially those connected to the Internet...

Recovering a Lost LVM Disk or Volume Group

I've reported on strange disk errors before and wasn't able to pin point the problem. Well, luckily I found what the problem but sadly I still don't know caused the problem to begin with...

Every now and then I ran into a server that won't (re)boot and fail with multiple reports of missing disks, ext2 or ext3 superblocks to be missing and to try e2fsck -b 8193. Result: the server cannot load some LVM Volume Group (VG) and the Logical Volume (LV) can't be found. Basically it means you've lost a disk. You have errors similar to this:
"Couldn't find all physical volumes for volume group vgdata."
"Couldn't find device with uuid '56pgEk-0zLS-cKBc-z9vJ-kP65-DUBI-hwZPSu'."
'Volume group "vgdata" not found'
LVM has several backup methods so not all is lost and chances are only the LVM meta data is corrupt, so the LVM manager doesn't know what to do with a physical disk and can't find its LVM signatures either. No…

Nagios 3.0 and Splunk

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I was just playing a test set-up for Nagios, to monitor some hosts, services and devices for me across the data center, when I ran into Splunk in a config file. Being naturally curious, I checked out Splunk...

Splunk is basically your IT search repository. It has a search engine that collects everything you want to track from all your servers. Use Splunk to collect SNMP traps, mail queues, log from web servers, firewall or routers, transaction and database logs and more. It can index anything because it uses live tracking. What it doesn't know but occurs frequently, you can teach it. Best of all, use Splunk to trigger an SNMP alert for a host or service in Nagios, when say more than 10 HTTP 404 errors occur on your corporate website. Probably there has been an error that some other system may or not have tried to inform you about... Excellent! Some assembly required of course, as everyone has different logs, needs, wishes and demands...