/dev/pts errors on newly created Xen DomUs (Debian Lenny)

December 10, 2009 · in ,

Today was the first time I had to create a new DomU after upgrading my Xen setup to Debian Lenny. When I booted the VM and logged in via xm console I got some strange errors when installing packages:

Can not write log, openpty() failed (/dev/pts not mounted?)

Additionally, after setting up SSH, I got the following error when logging in with SSH:

Server refused to allocate pty

Solution: install udev, reboot the VM and you’re good to go.

Backup Xen virtual machines with LVM snapshots and ftplicity/duplicity

July 8, 2009 · in , ,

Some time ago, I updated the backup system on a Server running multiple Xen VM instances (DomUs). Before changing the system, each virtual machine ran its own backup scripts to backup data to an external FTP server. Now, VMs are centrally backed up to FTP from the Dom0 using LVM (Logical Volume Manager) snapshots. As a backup solution I chose duplicity and ftplicity in combination with a shellscript to create automated LVM snapshots. Duplicity is a tool to create GPG-encrypted (this way you can store your backups at remote servers without having to worry about who has access to your data) incremental backups to remote servers, ftplicity is a wrapper script for duplicity which allows running duplicity without interaction (e.g. without the need to type any passwords). Ftplicity was originally published by the German computer magazine c’t, but has been undergone further development and is now hosted at SourceForge.

You can find tutorials on ftplicity/duplicity here (Note: they use the original c’t version of ftplicity):

Basically you can use this setup for any kind of LVM snapshot based system, but I’m focusing on backing up Xen VMs here. I assume you got your LVM and Xen system up and running so far. I did this on a Debian Lenny system, but it should be similar on other distros. I did all steps as root.

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Upgrade from Debian Etch/Xen 3.0 to Debian Lenny/Xen 3.2 (AMD64)

April 13, 2009 · in , ,

I was running a Xen server with Debian Etch as dom0 (Linux 2.6.18-6 with Xen 3.0.3-1 on AMD64) for some time now. Today, I decided to upgrade the dom0 to Debian Lenny (Linux 2.6.26-2 with Xen 3.2.1-2). The domUs are all running a Debian-based OS (3x Lenny, 1x Ubuntu Hardy). The upgrade was quite straightforward, however there were some pitfalls you can avoid in advance.

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Debootstrap a Ubuntu Hardy DomU on a Debian Etch Xen Dom0

October 3, 2008 · in , ,

Lately, I wanted set up a Ubuntu Hardy DomU on an existing Debian Etch Dom0 box. Usually, setting up Debian-based DomUs is very simple with xen-create-image and debootstrap (there are tons of tutorials out there dealing with this topic), but unfortunately Etch’s version of debootstrap doesn’t support Ubuntu Hardy. I spent a surprisingly long time on searching the net until I found a solution for this problem on a french site: Installer et configurer Xen sur Debian 4.0 Etch (it’s a complete howto for Xen on Debian Etch, but it deals with the Hardy part too). The author created a backport of the debootstrap package, which enables you to debootstrap Hardy.

First, you have to create the hardy.d directory (symlink) for xen-tools.

$ cd /usr/lib/xen-tools
$ ln -s ubuntu.d hardy.d

There’s a debian repository holding the backport package, however I got problems to use that repository on an amd64 box, so I downloaded and installed the package manually.

$ wget http://falcon.landure.fr/pool/etch/debootstrap/debootstrap_1.0.10_all.deb
$ dpkg -i debootstrap_1.0.10_all.deb

Now you should be able to debootstrap a Hardy DomU.

$ xen-create-image 
--hostname=hardy 
--ip=xxx.xxx.xxx.xxx 
--size=5Gb 
--memory=256Mb 
--dist=hardy 
--mirror=http://archive.ubuntu.com/ubuntu/