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Nikos Skalkotos authored
Make snf-image-creator be the dialog-based program and snf-mkimage be the command line one.
ebe0f1e0
Usage
snf-image-creator comes in 2 variants:
- snf-mkimage: A non-interactive command line program
- snf-image-creator: A user-friendly dialog-based program
Both expect the input media as first argument. The input media may be a local file, a block device or "/" if you want to create an image out of the running system (see host bundling operation).
Non-interactive version
snf-mkimage receives the following options:
$ snf-mkimage --help
Usage: snf-mkimage [options] <input_media>
Options:
--version show program's version number and exit
-h, --help show this help message and exit
-o FILE, --outfile=FILE
dump image to FILE
-f, --force overwrite output files if they exist
-s, --silent output only errors
-u FILENAME, --upload=FILENAME
upload the image to the cloud with name FILENAME
-r IMAGENAME, --register=IMAGENAME
register the image with a cloud as IMAGENAME
-m KEY=VALUE, --metadata=KEY=VALUE
add custom KEY=VALUE metadata to the image
-t TOKEN, --token=TOKEN
use this authentication token when
uploading/registering images
-a URL, --authentication-url=URL
use this authentication URL when uploading/registering
images
-c CLOUD, --cloud=CLOUD
use this saved cloud account to authenticate against a
cloud when uploading/registering images
--print-syspreps print the enabled and disabled system preparation
operations for this input media
--enable-sysprep=SYSPREP
run SYSPREP operation on the input media
--disable-sysprep=SYSPREP
prevent SYSPREP operation from running on the input
media
--print-sysprep-params
print the needed sysprep parameters for this input
media
--sysprep-param=SYSPREP_PARAMS
Add KEY=VALUE system preparation parameter
--no-sysprep don't perform any system preparation operation
--no-shrink don't shrink any partition
--public register image with the cloud as public
--tmpdir=DIR create large temporary image files under DIR
Most input options are self-describing. If you want to save a local copy of the image you create, provide a filename using the -o option. To upload the image to the storage service of a cloud, provide valid cloud API access info (by either using a token and a URL with -t and -a respectively, or a cloud name with -c) and a remote filename using -u. If you also want to register the image with the compute service of the cloud, in addition to -u provide a registration name using -r. All images are registered as private. Only the user that registers the image can create VM's out of it. If you want the image to be visible by other user too, use the --public option.
By default, before extracting the image, snf-mkimage will perform a number of system preparation operations on the snapshot of the media and will shrink the last partition found. Both actions can be disabled by specifying --no-sysprep and --no-shrink respectively.
If --print-sysprep is defined, the program will exit after printing a list of enabled and disabled system preparation operation applicable to this input media. The user can enable or disable specific syspreps, using -{enable,disable}-sysprep options. The user may specify those options multiple times.
Running snf-mkimage with --print-sysprep on a raw file that hosts a debian system, we print the following output:
$ snf-mkimage --print-syspreps ubuntu.raw
snf-image-creator 0.6
=====================
Examining source media `ubuntu_hd.raw' ... looks like an image file
Snapshotting media source ... done
Enabling recovery proc
Launching helper VM (may take a while) ... done
Inspecting Operating System ... ubuntu
Mounting the media read-only ... done
Collecting image metadata ... done
Umounting the media ... done
Enabled system preparation operations:
cleanup-cache:
Remove all regular files under /var/cache
cleanup-log:
Empty all files under /var/log
cleanup-passwords:
Remove all passwords and lock all user accounts
cleanup-tmp:
Remove all files under /tmp and /var/tmp
cleanup-userdata:
Delete sensitive userdata
fix-acpid:
Replace acpid powerdown action scripts to immediately shutdown the
system without checking if a GUI is running.
remove-persistent-net-rules:
Remove udev rules that will keep network interface names persistent
after hardware changes and reboots. Those rules will be created again
the next time the image runs.
remove-swap-entry:
Remove swap entry from /etc/fstab. If swap is the last partition
then the partition will be removed when shrinking is performed. If the
swap partition is not the last partition in the disk or if you are not
going to shrink the image you should probably disable this.
use-persistent-block-device-names:
Scan fstab & grub configuration files and replace all non-persistent
device references with UUIDs.
Disabled system preparation operations:
cleanup-mail:
Remove all files under /var/mail and /var/spool/mail
remove-user-accounts:
Remove all user accounts with id greater than 1000
cleaning up ...
If you want the image to have all normal user accounts and all mail files removed, you should use --enable-sysprep option like this:
$ snf-mkimage --enable-sysprep cleanup-mail --enable-sysprep remove-user-accounts ...
Dialog-based version
snf-image-creator receives the following options:
$ snf-image-creator --help
Usage: snf-image-creator [options] [<input_media>]
Options:
--version show program's version number and exit
-h, --help show this help message and exit
-l FILE, --logfile=FILE
log all messages to FILE
--tmpdir=DIR create large temporary image files under DIR
If the input media is not specified in the command line, in the first dialog box the user will be asked to specify it:

The user can select a file (regular or block device) or use the Bundle Host button to create an image out of the running system (see Host bundling operation).
After the input media is examined and the program is initialized, the user will be given the choice to run snf-image-creator in wizard or expert mode.
Wizard mode
When snf-image-creator runs in wizard mode, the user is just asked to provide the following basic information:
- Cloud: The cloud account to use to upload and register the resulting image
- Name: A short name for the image (ex. "Slackware")
- Description: An one-line description for the image (ex. "Slackware Linux 14.0 with KDE")
- Registration Type: Private or Public
After confirming, the image will be extracted, uploaded to the storage service and registered with the compute service of the selected cloud. The user will also be given the choice to keep a local copy of it.
For most users the functionality this mode provides should be sufficient.
Expert mode
Expert mode allows the user to have better control on the image creation process. The main menu can be seen in the picture below:

In the Customize sub-menu the user can control:
- The system preparation operations that will be applied on the media
- Whether the image will be shrunk or not
- The properties associated with the image
- The configuration tasks that will run during image deployment
In the Register sub-menu the user can provide:
- Which cloud account to use
- A filename for the uploaded diskdump image
- A name for the image to use when registering it with the storage service of the cloud, as well as the registration type (private or public)
By choosing the Extract menu entry, the user can dump the image to the local file system. Finally, if the user selects Reset, the system will ignore all changes made so far and will start the image creation process again.
Host bundling operation
As a new feature in v0.2, snf-image-creator can create images out of the host system that runs the program. This is done either by specifying / as input media or by using the Bundle Host button in the media selection dialog of snf-mkimage. During this operation, the files of the disk are copied into a temporary image file, which means that the file system that will host the temporary image needs to have a lot of free space (see large temporary files for more information).
Creating a new image
Suppose your host system is a Debian Wheezy and you want to create a new Ubuntu server image. Download the installation disk from the Internet:
$ wget http://ubuntureleases.tsl.gr/12.04.2/ubuntu-12.04.2-server-amd64.iso
Verify that it has been downloaded correctly:
$ echo 'a8c667e871f48f3a662f3fbf1c3ddb17 ubuntu-12.04.2-server-amd64.iso' > check.md5
$ md5sum -c check.md5
Create a 2G sparse file to host the new system:
$ truncate -s 2G ubuntu.raw
And install the Ubuntu system on this file:
$ sudo kvm -boot d -drive file=ubuntu.raw,format=raw,cache=none,if=virtio \
-m 1G -cdrom ubuntu-12.04.2-server-amd64.iso
Warning
During the installation, you will be asked about the partition scheme. Don't use LVM partitions. They are not supported by snf-image-creator.
You will be able to boot your installed OS and make any changes you want (e.g. install openssh-server) using the following command:
$ sudo kvm -m 1G -boot c -drive file=ubuntu.raw,format=raw,cache=none,if=virtio
After you're done, you may use snf-image-creator as root to create and upload the image:
$ sudo -s
$ snf-image-creator ubuntu.raw
In the first screen you will be asked to choose if you want to run the program in Wizard or Expert mode. Choose Wizard.

Then you will be asked to select a cloud and provide a name, a description and a registration type (private or public). Finally, you'll be asked to confirm the provided data.

Choosing YES will create and upload the image to your cloud account.
Limitations
Supported operating systems
snf-image-creator can only fully function on input media hosting Linux, FreeBSD (tested on version 9.1) and Windows (Server 2008 R2 and Server 2012) systems. The program will detect the needed metadata and you may use it to upload and register other Unix images, but you cannot use it to shrink them or perform system preparation operations.
Logical Volumes
The program cannot work on LVM partitions [1]. The input media may only contain primary or logical partitions.
Para-virtualized drivers
Most synnefo deployments 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 won't be able to boot.
Many popular Linux distributions, like Ubuntu and Debian, will automatically create a generic initial ramdisk file that contains many different modules, including the VirtIO drivers. Others that target more experienced users, like Slackware, won't do that [2]. snf-image-creator cannot resolve this kind of problems and it's left to the user to do so. Please refer to your distribution's documentation for more information on this. You can always check if a system can boot with para-virtualized disk controller by launching it with kvm using the if=virtio option (see the kvm command in the Creating a new image section).
For Windows and FreeBSD systems, the needed drivers need to be manually downloaded and installed on the media before the image creation process takes place. For FreeBSD the virtio drivers can be found here. For Windows the drivers are hosted by the Fedora Project.
Some caveats on image creation
Image partition schemes and shrinking
When image shrinking is enabled, snf-image-creator will shrink the last partition on the disk. If this is a swap partition, it will remove it, save enough information to recreate it during image deployment and shrink the partition that lays just before that. This will make the image smaller which speeds up the deployment process.
During image deployment, the last partition is enlarged to occupy the available space in the VM's hard disk and a swap partition is added at the end if a SWAP image property is present.
Keep this in mind when creating images. It's always better to have your swap partition placed as the last partition on the disk and have your largest partition (/ or /home) just before that.
Large temporary files
snf-image-creator may create large temporary files when running:
- During image shrinking, the input media snapshot file may reach the size of the original media.
- When bundling the host system, the temporary image file may became as large as the rest of the disk files altogether.
/tmp directory is not a good place for hosting large files. In many systems the contents of /tmp are stored in volatile memory and the size they may occupy is limited. By default, snf-image-creator will use a heuristic approach to determine where to store large temporary files. It will examine the free space under /var/tmp, the user's home directory and /mnt and will pick the one with the most available space. The user may overwrite this behaviour and indicate a different directory using the tmpdir option. This option is supported by both snf-image-creator and snf-mkimage.
Footnotes
[1] | http://sourceware.org/lvm2/ |
[2] | http://mirrors.slackware.com/slackware/slackware-14.0/README.initrd |