======================================== Debian DomU on the Jump Xen VPS platform ======================================== About this documentation ======================== This documentation is still evolving, please let us know if there's any way we can improve it - if any of it is difficult to understand, or you think could be improved, let us know - preferably with suggested modifications. Please read through the whole document at least once before proceeding. Pricing ======= GBP250/year for a virtual machine, 2x 64-bit vCPUs, 80GB RAID backed HDD space, 1GB RAM, and 1Mbps 95%ile bandwidth allowance on 1Gbps connection to the server - not rate limited. GBP30/year per additional 256MB RAM GBP30/year per additional 20GB RAID backed disk space All prices exclude VAT, and are invoiced annually in advance. Refunds for unused portions of a year are available should you discontinue service. About the Virtual machine environment ===================================== The hypervisor is the 64bit version of the Xen virtual machine monitor version 3.1. The host machine is a Sun Fire X2200 M2, currently with 30GB of RAM, and two dual-core 1.8GHz Opteron 2210. The disk subsystem is a SCSI320 attached RAID array - Infortrend EonStor A04U-G2421 with 1GB of cache, and 4x 500GB WD RAID edition SATA disks configured in a RAID5 array. The Dom0 is Debian 4.0 - etch. Guest machines are by default configured with 1GB of physical RAM, two virtual CPUs, and 80GB of disk space - which is mapped to an LVM logical volume on the host Dom0, and appears as /dev/hda on the guest DomU. LVM allows the disk to be easily extended should you require more space later on. The plan in November 2008 is to comission a second system, a Sun Fire X4150, with two quad core Xeon CPUs, specifically the Low Voltage L5420 2.5GHz models. The disk array will be upgraded to a 16 disk Infortrend iSCSI chassis, which has dual redundant PSUs, controllers and 4GB of battery backed cache. Accessing the admin console =========================== To access the admin console of your Xen DomU virtual machine, you'll need to ssh to vps-tfm4.jump.net.uk. Remember to set your terminal type to utf-8 The username and password will have been forwarded to you separately. The IPs able to access the admin console are restricted in hosts.allow, so please supply us with details of the range(s) you may wish to access the admin console from in future. For now, you'll be able to reach it from your existing colo box since the whole Jump range is allowed. Running the debian installer ============================ Once logged into the admin console, you can choose which VM image you want to control, type 'list' and you'll see two choices for which Xen configuration you want to control; your normal machine configuration, and a configuration set to boot into the debian installer (with -install appended to the machine name). Type 'control' followed by the name of the -install configuration, then 'boot' to start the image, then 'console' to attach to the console. It's initially configured to boot into the debian installer, which will let you configure things however you like. Including letting you partition your disks, such as with LVM if you like. You can even choose to encrypt your disk, but be aware that you'll need to log in to the admin console whenever the guest is rebooted in order to type in the password for the filesystems. You'll get an error when setting the keyboard layout, just ignore this. You will need to configure the network manually - your virtual machine will be on the same VLAN as your existing colocated server(s), so pick an unused IP address from your range, and use the same netmask and default gateway. Feel free to use 212.13.202.71 as a resolver. You'll need to choose to continue without loading some kernel modules in the installer at the next point too, don't worry about this. When configuring your disks, you'll see several error messages of 'Could not get identity of device /dev/hda - Invalid argument' - simply because hda isn't a real device, and can't be accessed like one for some things. If you're ever likely to want to grow your virtual disk, the end of the disk is extended, thus you may want to configure your LVM partition as the last partition on the disk assuming you'd want to grow the LVM volume, if you don't use LVM, then put whichever partition you're most likely to grow at the end of the disk. Obviously you're unlikely to need the 'Desktop environment' software set! We recommend you do install grub, although it's not used, it does make it easy to obtain the necessary root= line for the Xen configuration, which depends on how you've partitioned your machine, it may also be useful if you later need to move from the virtual machine to having your own physical machine or a different virtualisation platform. Before rebooting from the debian installer ========================================== At the 'Installation complete' Go Back or Continue screen, choose Go Back, as Continue will reboot the system before the following information is gathered: We need to know what root= to set in the Xen configuration, this will be in the menu.lst file in the grub directory. The easiest way to do this is to execute a shell, then do the following: grep kopt=root /target/boot/grub/menu.lst When you have recorded that information, exit from the shell and choose finish the installation. If the root= line happened to be equivilent to root = 'root=/dev/mapper/yourhost-root ro' then the standard main config for your VM may work fine, if not, reply to the ticket with what root device line you need, and we'll reconfigure the Xen DomU with that root device. Booting into the main configuration for your VM =============================================== Finishing the installation should have dropped you back to the admin console, where you can shutdown the installer by typing 'shutdown', then control the main image with 'control' followed by the name of the non -install configuration (type 'list' if you've forgotten), followed by 'boot'. If you forget to shutdown the -install image of your vm before trying to start the normal image, you'll be greeted with a message informing you that "Device /dev/$hostname/$vps-name is mounted in a guest domain, and so cannot be mounted now." After booting the normal system =============================== Remember to do 'apt-get install linux-image-2.6.18-6-xen-amd64' which should install the kernel modules appropriate to the kernel being run. Being neighbourly ================= Remember your machine shares resources (IO, CPU, etc) on the host machine with other virtual machines, so please try not to unnecessarily waste resources. We ask you to agree to the following: * Performance testing - please avoid saturating resources for the sake of performance testing, instead try to monitor performance as a byproduct of normal functioning (eg time it took for a database query to return, etc). * Swap - if you're regularly running into swap, please speak to us and arrange for more RAM for your virtual machine, IO exhaustion on the disk subsystem ruins the day for everyone.