Archive for August 2008

Finding Disk ID on a Raw Device Mapping in ESX

vmkfstools is your friend. In ESX 2.5.x you can use the switch “-P” on the “mapping”-file to show you details of the RDM.

# vmkfstools -P /vmfs/FileSystem1/somemachinesdiskfile-META.vmdk

in VI3 the switch has changed to “–queryrdm” or just “-q” for short.

# vmkfstools -q /vmfs/FileSystem1/somemachinesdiskfile.vmdk

Howto change MTU in Red Hat Linux

In Red Hat Enterprise Linux you can change the MTU (Maximum Transmission Unit) dynamically

# ip link set mtu eth0 512

or using ifconfg

# ifconfig eth0 mtu 512

but to make it permanent even after a reboot you need to add the MTU setting to the correct interface configuration file.

continuing the above examples, that would be:





Qlogic HBA WWN’s in SLES 9/10

If using Qlogic HBAs in SLES 9, the recommended driver is the vendors own driver. In this case wwn's as well as wwpn's could be found by looking in /proc/scsi/qla2xxx
# cat /proc/scsi/qla2xxx/* | grep node


# cat /proc/scsi/qla2xxx/* | grep adapter-port

In SLES 10 the native HBA driver is the recommended. You can find WWNs and WWPNs by looking in /sys/class/fc_host or using the systool

# cat /sys/class/fc_host/host?/node_name


# systool -c fc_host -A "node_name"


This Blog is not really a blog. It is meant as place to write tech stuff that I would otherwise forget. So it’s pretty much a private bulletin board.

On the other hand; If this collection – by any chance – can help somebody “out there”, it would be downright stupid not making it public. With the added bonus that I can access my “memory” from anywhere as long as I’m online (which is pretty much allways).

There’s not much (read: nothing) in this collection yet, but there will be shortly, and it will be a work in constant progress.