Categories Archives: Uncategorized

Grub with Xen Guests

In order for grub to ‘see’ virtual disks, you have to tell it about them with the ‘device’ command: # grub grub> device (hd0) /dev/xvda grub> root (hd0,0) grub> setup (hd0) grub> quit Keep in mind, installing grub on the MBR is not always necessary with Xen PV guests, but is highly useful for V2P […]

XenServer 6.2 with Software RAID

Historically XenServer does not support software RAID out-the-box, and this is unchanged in the latest 6.2 release. We can convert it to RAID after installation. First we set up the 2nd disk by copying the partition tables whilst enabling a degraded RAID on it, then copy data over with custom initrd. sgdisk -R/dev/sdb /dev/sda # […]

JWplayer iframe codes for Wowza

Allows easy embedding of on-demand and live media from a Wowza server using Iframes and a PHP server capable of .htaccess rewrite rules. http://djlab.com/stuff/jwplayer.zip Example of embed code: <iframe src=”http://mysite.com/jwplayer/Sportswire/sw-584-1.mp4?autoPlay=0&poster=http://mysite.com/images/poster.jpg” frameborder=”0″ scrolling=”no” width=”432px” height=”320px”></iframe>

Removing RAID metadata

Sometimes a hardware RAID controller or fakeraid (BIOS) can leave metadata that makes it impossible to install Windows or Linux, or it installs correctly, but causes a kernel panic or a 0xb7 blue screen error on the first boot. The only method I could find to delete the metadata *quickly* is to zero out the […]

MySQL Relationships (JOIN explained)

The visual diagrams still confuse me after so many years and I always forget…so here it is: INNER JOIN gets all records from one table that have some related entry in a second table LEFT JOIN gets all records from the LEFT linked table but if you have selected some columns from the RIGHT table, […]

Pacemaker / Corosync / DRBD Cheatsheet

Monitor the status: crm_mon Migrate all resources to another node: crm resource migrate rg_main <fqdn_node_name> Take node offline and online (be careful, this sets a ‘prefer’ to the other node to force a transition, which may or may not get removed afterwards): crm node standby crm node online Start and stop all resources (warning, this […]