KeyWords: SysAdmin, Xen

xen-strap

Kudos to Marian Klein for writing the truly amazing script xen-strap! It can bootstrap a Xen DomU based on any of: Scientific Linux 4.x/5.x (also in the CERN variants), CentOS 4.x/5.x, or Debian etch/lenny/sid. And all of this in one single script with no dependencies - just download and run. It hasn't been from the C64 times that I have seen a tool requiring no configuration at all!

Last but not least, it install a truly minimal system: no need to have X11 or other fat daemons running on VMs...

Here is the incantation I used to build a template SL4.7 DomU:

  /root/xen-strap --name=sl4-template \
    --memory=1024 \
    --size=8G \
    --label=root \
    --noswap \
    --mac=00:16:3E:00:66:01 \
    --dhcp \
    --ssh \
    --update \
    --locales-en-only \
    --dwc --no-ntp \
    --post-install="host:/var/cfengine/scripts/newmachine" \
    sl47 \
    lvm:vg_root/sl4template:8G \
    ftp://mirror.switch.ch/mirror/scientificlinux/47/i386/SL/RPMS/

• --name is the name of the Xen configuration generated in /etc/xen, and also the hostname (unless overridden with --hostname)
• --size is the size of the partition/LV that xen-strap will create for hosting the VM's root filesystem;
• --label is the label of the VM root filesystem (as seen from inside the VM);
• --noswap turns off creating a swap partition for the VM;
• --mac...= sets the MAC address (not in the mainstream xen-strap, you need to apply the patch below)
• --dhcp will configure the DomU to use DHCP for networking;
• --ssh will install and enable the SSH server on the DomU;
• --update will start an OS update after everything has been installed;
• --locales-en-only will remove non-English locales, saving some space on the DomU disk;
• --dwc --no-ntp turns off the NTP daemon in the DomU (will use the clock in the Dom0, no worry);
• --post-install="host:/path/to/script" runs the post-install script found on the Dom0 at /path/to/script;
• sl46 is the distribution to install (Scientific Linux 4.7, you need to apply the patch below - stock xen-strap only has 4.6)
• lvm:... creates the specified LV to host the DomU root filesystem;
• the rest is the OS mirror URL - if you don't specify it, you get ==xen-strap=='s default choice (which is in the UK).

The long story and explanations can be found in the GridPP Wiki: http://www.gridpp.ac.uk/wiki/Xen-strap

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