On Linux qemu-nbd can be used to access disk images in different formats as if they were block devices. For example, to mount a VHD file run To unmount and disconnect the nbd device run
Currently the Fedora projects provides cloud images as qcow2 and raw disk files. Microsoft’s Azure however only supports VHD files. Fortunately qemu-img can convert between those formats: Note that the subformat options fixed and force_size are required for Azure to be able to use the disk image since Azure only supports fixed sized disks.
Migrating a virtual machine from one host to another is usually no big deal if both hosts run the same VMM. But what if one wants to move a VM from a host running a different hypervisor than the target host? In the case of moving a VM from KVM to ESXi that’s just not (easily) possible. However, one can… Read more »
Create a new image file (10GiB): (Note: You can also create a sparse file with dd’s seek option. Have a look at the dd manpage or the examples on http://en.wikipedia.org/wiki/Dd_(Unix)) Create the new filesystem: Label the filesystem: Edit the DomU’s config file, /etc/xen/<hostname>.cfg and add the new disk: Start the VM: Edit DomU’s /etc/fstab & mount the disk:
Just a little memory hook: When a Xen DomU hangs at “Checking for hardware changes”, it is probably due to a dead xenconsoled process on the Dom0. This happens from time to time but should immediately fix the hanging DomUs.
Every X server internally manages an ACL (Access Control List) of those hosts, that are allowed to connect. The server only authorizes connections from X clients, whose host is on that list and rejects access to all others. The xhost program is used to add or revert access to the X server for specified hosts. It’s also possible to specify… Read more »
When an upgrade includes changes to a default configuration file, the package will write either a .rpmnew or a .rpmsave file instead of overwriting the configuration file on your system. Which file a package creates is up to the discretion of the package maintainer. From “Dealing with .rpmnew and .rpmsave files” By Bruce Byfield: An .rpmnew file contains the new… Read more »
Sometimes, packages you never actually use get installed as dependency by yum (or even during initial installation by anaconda). package-cleanup is a great tool that helps you find packages not required by other packages. It it part of the yum-utils package which can easily be pulled with yum: 1. Find and review “unused” packages You can find packages not required… Read more »
To update the initrd.img to load additional drivers early in the boot process, normally you would simply run /sbin/mkinitrd and let the script do the work. But what if the initrd.img used during the installation of CentOS lacks an important driver? Maybe you want to netboot CentOS, but the initial ramdisk CentOS provides doesn’t have the right modules for you… Read more »
I already wrote a little article, how to boot a FreeDos via PXE. Of course, you can boot Fedora (or CentOS) in like manner.