From 1e72da952348c62a3d96b6c97f23e54da03dd9e0 Mon Sep 17 00:00:00 2001 From: Alex Pyrgiotis Date: Thu, 13 Dec 2012 16:24:30 +0200 Subject: [PATCH] Restore original image creation example Also, add a warning about LVM, the need for openssh-server, memmory parameter for KVM and md5sum for the dowloaded iso. --- docs/usage.rst | 342 +++++++++++--------------------------------------------- 1 file changed, 68 insertions(+), 274 deletions(-) diff --git a/docs/usage.rst b/docs/usage.rst index 90cf460..2199116 100644 --- a/docs/usage.rst +++ b/docs/usage.rst @@ -194,311 +194,105 @@ By choosing the *Extract* menu entry the user can dump the image to the local file system and finally, if the user selects *Reset*, the system will ignore all changes made so far and will start the image creation process again. -Usage example -============= - -Supposing you have snf-image-creator installed on a machine (hereafter referred -to as your **host machine**), you can follow the next steps to upload and -register an image of an OS of your preference (hereafter referred to as your -**guest OS**) to your synnefo deployment. - - * `Step 1: Install the guest OS`_ - * `Step 2: Create and upload an image of the guest OS`_ - * `Step 3: Create your VM`_ - - -Step 1: Install the guest OS ------------------------------ - -The guest OS has to be installed on a media such as a block device or a regular -raw file, that can be **accessible** by your host machine. - -But why is accessible empasized? Well, because you don't need to do the -installation of the guest OS on your host machine. You can just as well install -it on a raw file, upload it on Pithos+, download it on your host machine and -use it for Step 2. - -*Note: If you have a guest OS already installed, you may want to skip the -next step. However, be sure to check out the* `Caveats`_ *section, where -some requirements about the guest OS are presented.* - -Installation example -"""""""""""""""""""" - -To simplify things a bit, we will install the guest OS on the host machine -where snf-image-creator is installed. We will assume that the host machine is -an Ubuntu 12.04 ~okeanos VM, built with max specifications (4 CPUs, 2GB of -ram, 40GB of disk space at the time of writing this). - -*Note: Since the installation of the guest OS will take place on your host -VM, you must be able to connect to it graphically. This is covered by our* -`connection guide `_. +Creating a new image +==================== -For our guest OS, we will choose, Linux Mint, which is the most hyped Linux -OS according to Distrowatch. A new version has just been released, so -this seems like a fine choice. :: +Suppose you want to create a new Ubuntu server image. Download the installation +disk from the Internet: - Warning: The installation might take a long time (~1 hour) and a bit of - lagginess due to nested virtualization is to be expected. +.. code-block:: console -Fire up your terminal, go to your home directory and type the following to -download the Linux Mint live cd:: + $ wget http://ubuntureleases.tsl.gr/12.04.1/ubuntu-12.04.1-server-amd64.iso - $ wget http://ftp.ntua.gr/pub/linux/linuxmint//stable/14/linuxmint-14-mate-dvd-64 bit.iso +Verify that it has been downloaded correctly: -Verify that it has been downloaded correctly. If the following command -prints "OK". then you are good to go:: +.. code-block:: console - $ echo 'b370ac59d1ac6362f1662cfcc22a489c linuxmint-14-mate-dvd-64bit.iso' > check.md5 + $ echo 'a8c667e871f48f3a662f3fbf1c3ddb17 ubuntu-12.04.1-server-amd64.iso' > check.md5 $ md5sum -c check.md5 -Allocate a few gigs of space to create a sparse file:: - - $ truncate -s 7G linuxmint.raw +Create a 2G sparce file to host the new system: -Use `kvm` to boot the Live CD:: - - $ sudo kvm -m 1200 -smp 4 -boot d -drive \ - file=linuxmint.raw,format=raw,cache=none,if=virtio \ - -cdrom linuxmint-14-mate-dvd-64bit.iso +.. code-block:: console - At a glance, let's see what the above options do: - -m 1200: Use 1200MB of RAM for the guest OS. You should - allocate as much as possible - -smp 4: Simulate an SMP system with 4 CPUs for the - guest OS to use. - -boot d: Place cdrom first in the boot order - file=opensuse.raw Use this raw file as the "hard disk" for the - installation - if=virtio: Inform the OS that it should preload the - VirtIO drivers (more on that on `Caveats`_ - section) - -cdrom linuxmint-14-mate-dvd-64bit.iso: - "Insert" Linux Mint's live cd in the cdrom - drive + $ truncate -s 2G ubuntu_hd.raw -Wait a few seconds and then a new screen with the Linux Mint logo should -appear. You don't have to press any key since it will boot automatically to -Linux Mint's live desktop after a few minutes. +And install the Ubuntu system on this file: -|qemu-live| +.. code-block:: console -Choose "Install Linux Mint". The installation process should be pretty -straightforward. Just keep two things in mind: + $ sudo kvm -boot d -drive file=ubuntu_hd.raw,format=raw,cache=none,if=virtio \ + -m 1000 -cdrom ubuntu-12.04.1-server-amd64.iso -* The username you choose will also be used later on, when you create a VM - from this OS image. The password, however, will be removed and you will - be given a new one. -* The installed OS must have no more than one primary partition and - optionally a swap partition. You can read more in the `Caveats`_ - section below. You don't have to worry about it in this installation - however, since the default option takes care of that. +.. note:: - |qemu-partition| + During the installation, you will be asked about the partition scheme. Since + snf-image-creator does not support LVM partitions, you are advised to create + regular partitions. -After the installation is complete, you can close the QEMU window. You +When the installation is complete, you can close the QEMU window. You will be able to boot your installed OS and make any changes you want to it -using the following command:: - - $ sudo kvm -m 1200 -smp 4 -boot d -drive \ - file=linuxmint.raw,format=raw,cache=none,if=virtio - -At the very least, you should install OpenSSH server to connect to your VM -properly. You can install OpenSSH server using the following command:: - - $ sudo apt-get install openssh-server - -Bear in mind that once the OS image has been uploaded to your synnefo -deployment, you will not be able to make changes to it. Since you can only -apply changes to your raw file, you are advised to do so now and then proceed -to Step 2. - -Caveats -""""""" -This is a list of restrictions you must have in mind while installing the -guest OS: - -**Partitions** - -The installation must consist of no more than one primary partition. It -can have a swap partition though, which should ideally - but not -necessarily - be located at the end of the media. In this case, the -uploaded image will be much smaller and the VM deployment process much -faster. - -**VirtIO drivers** - -Depending on your synnefo-deployment, you may need to use para-virtualized -drivers for your storage and network needs. - -~okeanos uses the VirtIO framework which is essential for the ~okeanos VMs -to work properly since their disk I/O controller and Ethernet cards are -para-virtualized. - -Fortunately, you will not need to deal with the installation of VirtIO drivers -directly, since they are included in Linux kernel since version 2.6.25 and -shipped with all the modern Linux distributions. However, if the VirtIO drivers -are built as a module (and most modern OSes do so), they need to be preloaded -using an initial ramdisk (initramfs), otherwise the VM you create from this OS -image will not be able to boot. - -Debian derivatives will create an initial ramdisk with VirtIO included if -they are connected during the installation on a para-virtualized interface -(the "if=virtio" option in the Linux Mint example). - -In many other distros though, this is not the case. In Arch Linux for -example, the user needs to manually add virtio_blk and virtio_pci drivers -in /etc/mkinitcpio.conf and rebuild the initial ramdisk to make the -virtio drivers get preloaded during boot. You can read more in the `Arch -Linux wiki `_ on how to do it. - -For now, snf-image-creator cannot resolve this kind of problems and it's -left to the user to do it. - -Step 2: Create and upload an image of the guest OS --------------------------------------------------- +(e.g. install openssh-server) using the following command:: -This is the step on which we use snf-image-creator. There are actually two -variants of snf-image-creator, `snf-image-creator`_ and `snf-mkimage`_, both -achieving the same results but suited for different needs. Their scope is -documented at the start of the `Usage`_ section of this document. + $ sudo kvm -m 1000 -drive file=linuxmint.raw,format=raw,cache=none,if=virtio -*Note: Both tools take a snapshot of the installed OS on the media -provided to them. So, any changes they apply do not affect the OS -installed on the original media.* +After you're done, become root, activate the virtual environment you have +installed snf-image-creator in, and use *snf-mkimage* to create and upload the +image: -Let's see both tools in action. We will use them to create an image of the -Linux Mint 14 OS we installed in Step 2. - -snf-mkimage -""""""""""" - -In order to use snf-mkimage, simply type:: - - $ sudo snf-mkimage linuxmint.raw - -snf-mkimage will initially check if the media is indeed a single disk -partition or a raw file representing a hard disk. Then, it will use -heuristics to understand which OS has been installed on the media. After -that, you will be asked which mode you prefer. - -|mkimage-wizard| - -* Wizard mode is intuitive and consists of 4 simple steps. -* Expert mode has an abundance of options but requires a bit of knowledge - of the inner workings of Cyclades from your part. You can learn more on the - `Expert Mode`_ section of snf-mkimage. - -For our tutorial, we will use Wizard mode. So, choose "Wizard" and then provide -a name for the image. - -|mkimage1| - -This name will appear on Pithos+ and on the Public Images section of Cyclades. - -Then, provide a description for the image. - -|mkimage2| - -This will appear under the chosen image name on the Public Images section of -cyclades. - -Next, add your account e-mail - -|mkimage3| - -... your account token... - -|mkimage4| - -...and you're done! A list operations will appear on your console. - -|mkimage-results| - -We will briefly comment on the above output. - -* **Sysprep:** Operations from 1/9 to 9/9 are part of the system - preparation operations and are best explained in the snf-image-creator's - `sysprep`_ section. -* **Shrinking:** When shrinking the image, we check if a swap partition - exists at the end of the media. If this is the case, it will be removed - and re-inserted upon the deployment process of the VM. Alternatively, if - the swap partition lies at the start of the media, it will be left - untouched. On both cases, the primary partition will be shrunken as much - as possible. On this example, we can see that the final size is 3.5GB, - whereas the orginal size was 7GB. This means that the image was reduced - by half, a pretty impressive feat. -* **MD5SUM:** The md5sum of the image is used later on to verify that the - image has been uploaded successfully. -* **Uploading:** Everytime you upload an OS image, every block is hashed, - checked against existing blocks in Pithos+ and finally uploaded, if no - other block has the same hash. - - *Consider this example: You have just uploaded a Gentoo Linux image but - had forgotten to install a necessary package. In this case, you would - probably edit the OS in the raw file and then use snf-mkimage to upload - the new image. However, since there is an almost identical image already - uploaded on Pithos+, you can just as well upload only the blocks that - differentiate those two images. This is both time and space efficient.* - -Finally, after the image has been uploaded successfully, you will be asked -whether you want to save a local copy of the **shrunken** image. This is -just a copy of the diskdump that has been uploaded to Pithos+ and, in case -you are confused, the original OS installed on the media (linuxmint.raw in -our example) remains intact. - -snf-image-creator -""""""""""""""""" - -snf-image-creator is the command-line equivalent of snf-mkimage. All the -info provided in the steps above are given now as options, which makes it -ideal for scripting purposes. The full set of options can be found in the -`Usage section <#non-interactive-version>`_ of snf-image-creator's -documentation. - -This tool is most commonly used with the following set of options:: - - $ sudo snf-image-creator linuxmint.raw -a user@email.com \ - -t hUudl4DEIlomlnvWnv7Rlw== -u linuxmint.diskdump -r "Linux Mint 14 Nadia" - -As you can see, these options are exactly what snf-mkimage's steps -translate to. You can also see that the output is nearly identical: - -|image-creator| - -Step 3: Create your VM ----------------------- - -Creating a VM out of an uploaded custom image is a fairly simple task. -Just select "New Machine", go to "My Images" section and select your -image. +.. code-block:: console -|custom-vm| + $ sudo -s + $ source /path/to/snf-image-env/bin/activate + $ snf-mkimage ubuntu_hd.raw -Alternatively, if you want to create a VM from another user's custom -image, you can go to the "Public Images" section. +In the first screen you will be asked to choose if you want to run the program +in *Wizard* or *Expert* mode. Choose *Wizard*. -.. |qemu-live| image:: /snapshots/qemu-live.png +.. image:: /snapshots/01_wizard.png -.. |qemu-partition| image:: /snapshots/qemu-partition.png +Then you will be asked to provide a name, a description, an *~okeanos* account +and the token corresponding to this account. After that you will be asked to +confirm the provided data. -.. |mkimage-wizard| image:: /snapshots/mkimage-wizard.png +.. image:: /snapshots/06_confirm.png -.. |mkimage1| image:: /snapshots/mkimage1.png +Choosing *YES* will create the image and upload it to your *~okeanos* account. -.. |mkimage2| image:: /snapshots/mkimage2.png +Some caveats on image creation +============================== -.. |mkimage3| image:: /snapshots/mkimage3.png +Para-virtualized drivers +------------------------ -.. |mkimage4| image:: /snapshots/mkimage4.png +*~Okeanos* uses the *VirtIO* framework. The disk I/O controller and the +Ethernet cards on the VM instances are para-virtualized and need special +*VirtIO* drivers. Those drivers are included in the Linux Kernel mainline since +version 2.6.25 and are shipped with all the popular Linux distributions. The +problem is that if the driver for the para-virtualized disk I/O controller is +built as module, it needs to be preloaded using an initial ramdisk, otherwise +the VM will not be able to boot. -.. |mkimage-fin| image:: /snapshots/mkimage-fin.png +In the image creation demonstration above, we initially installed the Ubuntu +system on a hard disk (*ubuntu_hd.raw*) that was connected on a +para-virtualized interface (pay attention to the *if=virtio* option of the kvm +line). Ubuntu and Debian create a generic initial ramdisk file that contains +many different modules, including the VirtIO drivers. In many distros this is +not the case. In Arch Linux for example, the user needs to manually add +*virtio_blk* and *virtio_pci* drivers in */etc/mkinitcpio.conf* and rebuild the +initial ramdisk [#f1]_ to make the virtio drivers get preloaded during boot. +For now, *snf-image-creator* cannot resolve this kind of problems and it's left +to the user to do it. -.. |mkimage-results| image:: /snapshots/mkimage-results.png +Swap partitions +--------------- -.. |image-creator| image:: /snapshots/image-creator.png +If you want your image to have a swap partitions, make sure this is the last +partition on the disk. If snf-image-creator detects a swap partition in the end +of the input media, it will remove the partition when shrinking and will save +enough information to be able to recreate it during image deployment. This will +make the image smaller and will speed up the deployment process. -.. |custom-vm| image:: /snapshots/custom-vm.png +.. rubric:: Footnotes +.. [#f1] https://wiki.archlinux.org/index.php/KVM#Paravirtualized_guests_.28virtio.29 -- 1.7.10.4