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Showing posts from January, 2009

Multipathd device enumeration

Testing my new kickstart file to install Linux on my old Poweredge 2950 dell servers is fine, but multipath presents me with a new problem.

We boot from SAN, even though the servers have local disks available. Eventually we will move towards Blades, so the experience is useful. But each server has a different number of LUNs available to it. The boot LUN is always LUN id 0. Without multipathd, this gave me /dev/sdb as the boot device. With multipathd, this gives me /dev/mapper/mpathX, where X is the number of LUNs I have. You may see the problem:
The kickstart file must list the boot drive order and designate a place to put the MBR. However, I can't think of a way to tell kickstart to use the last mpath device... I wish there'd be a way to make /dev/mapper/mpath0 the boot LUN...

Update: Well, it seems to be a limitation of multipath support in anaconda. I've booted the OEL 5.3 DVD ISO on 3 different bare metals and each server has a different number of LUNs associated with it…

Multipath Kickstart Options in RHEL 5.3

With Red Hat and Oracle Linux supporting multipathed installation from 5 update 2 on, I thought they should have changed the Kickstart Options as well, so that anaconda can be given the right parameters.

And I was right. ignoredisks has been added to let the installer ignore SAN disks as well as for cluster setups. multipath has been added to handle dual HBAs cases where the same disk will be seen over two different paths.

Update: except ignoredisks, there is really not much you need to do but boot the Linux kernel with the option 'mpath'. The multipath option lets you set/configure the multipath.conf configuration, I believe. Not used yet. In my case, I use this line to boot Linux and start a kickstart installation:
linux mpath text nousbstorage ksdevice=eth0 ks=http://server/mpathks.cfg
That's it. The first activates multipath-aware option in anaconda. The second uses text mode. The third parameter skips any USB devices in my PowerEdge 2950 (virtual floppy, disk and cdro…

Dell OpenManage and their TTY logs

Dell's OpenManage tools keep some logs under /var/log and do not clean them up. You also can't turn them off and they contain important info from the PERC controllers.

Anyway, the mailing list mentions this often, so I thought I post a little solution using logrotate: Dell OpenManage and their TTY logs.

/var/log/TTY_*.log {
daily
notifempty
missingok
rotate 7 # how many you want to save
compress
delaycompress
sharedscripts
postrotate
/usr/sbin/invoke-rc.d dsm_om_shrsvc restart >/dev/null 2>&1 || true
endscript
}

See also Planet Malaysia.

VMware Advanced Technical Training now free

As we run 700+ VMs in our data center, 40% of which Linux BTW, this news is pretty relevant to me: VMware decided to make their Advanced Technical Trainings (PDF) - mainly used for in-house support staff and engineers - available for free! Previous VCP certification is recommended, or at least thorough experience with VMware.

Source: VMware - VMware Partner News

Active Directory comes to Linux with Samba 4

Computerworld has a great read about Samba 4 and how it'll improve AD integration of Linux and MS AD. Although it's been possible for a long time, bundled SAMBA version in distos can run behind the main development line and become a pain when trying to read documentation and configure older versions. SAMBA4 will run most things out of the box:
Bartlett admitted Samba has a "nasty" reputation for being "impossible to configure" and believes Samba 4 should "just work" without administrators needing to read through documentation first.

"For example, in Samba 4 we generate the DNS configuration and have an optional OpenLDAP backend and we have configured this as we know how Samba needs this setup."

Over the past year Samba 4 has added multi-master replication leveraging OpenLDAP, making Samba no longer a single-server implementation.

"Our users have also demonstrated how smart card logins work. I barely had to do anything in Samba 4 to get …

Understanding LDAP - Design and Implementation

Central user administration has been a long desired feature by me for our data center. MS AD does it all for Windows, but Linux has been all stand-alone so far. I tried to do something quick with NIS in the past, but it never quite took off. So it's just me own (mngt and monitoring servers).

For this year, Identity Management was made an issue. However, which one is still up in the air. AD, Oracle's OID, Centrify or just plain an simple standard openLDAP? From my own experiences, openLDAP is great but distributions are behind on the latest official releases and this can wreak havoc in some obscure but critical situations.

So time to read up on the subject. Someone recommended the IBM Redbook Understanding LDAP - Design and Implementation to me... Interesting!

Check status of Linux network bonding

If you have configured bonding of two or more physical interfaces in a logical bonded interface capable of fail-overs, and you want to know the status of the bond, check /proc!

/proc/net/bonding/bond0 shows the status of the bond:
$ cat /proc/net/bonding/bond0 Ethernet Channel Bonding Driver: v2.6.3-rh (June 8, 2005) Bonding Mode: fault-tolerance (active-backup) Primary Slave: None Currently Active Slave: eth0 MII Status: up MII Polling Interval (ms): 100 Up Delay (ms): 0 Down Delay (ms): 0 Slave Interface: eth0 MII Status: up Link Failure Count: 1 Permanent HW addr: 00:1a:a0:34:73:dc Slave Interface: eth4 MII Status: up Link Failure Count: 1 Permanent HW addr: 00:15:17:38:b9:2a

OMSA debian packages for use with Ubuntu

Someone on the Dell mailing list was kind enough to point that although OMSA (OpenManage) on Ubuntu is not supported by Dell, the SARA institute in the Netherlands has a couple of OMSA Debian packages for Ubuntu ready for use. Check their site!

Back from vacation

I'm back from a 3 week vacation, so that explains the radio silence here.

This year we'll upgrade from OEL 4.5 to OEL 5.x, upgrade OEM to OEM 10.2.4 and start using Oracle RAC on our Dell Poweredge 2950 servers. We'll also upgrade to ESX 3.5 everywhere and use EMC Networker backups. And finally, management of some serious Sun hardware (T2000, M5000, M9000) will fall under our responsibility so all our deployment scripts will be updated to fit that platform as well.

Lots of other minor tweaks coming up too, so it should be an interesting year again. Subversion is almost fully integrated and we've been working towards release cycles for this year, to help streamline releases management and new features.