[snf-image-creator] / docs / usage.rst

Usage
^^^^^

snf-image-creator comes in 2 variants:
 * snf-image-creator: A non-interactive command line program
 * snf-mkimage: A user-friendly dialog-based program

Non-interactive version
=======================

snf-image-creator receives the following options:

.. code-block:: console

 $ 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
  -o FILE, --outfile=FILE
                        dump image to FILE
  -f, --force           overwrite output files if they exist
  -s, --silent          silent mode, only output errors
  -u FILENAME, --upload=FILENAME
                        upload the image to pithos with name FILENAME
  -r IMAGENAME, --register=IMAGENAME
                        register the image with ~okeanos as IMAGENAME
  -a ACCOUNT, --account=ACCOUNT
                        Use this ACCOUNT when uploading/registering images
                        [Default: None]
  -m KEY=VALUE, --metadata=KEY=VALUE
                        Add custom KEY=VALUE metadata to the image
  -t TOKEN, --token=TOKEN
                        Use this token when uploading/registering images
                        [Default: None]
  --print-sysprep       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
  --no-sysprep          don't perform system preparation
  --no-shrink           don't shrink any partition


Most input options are self-describing. If you want to save a local copy for
the image, you need to specify *-o* option. In order to upload the image to
pithos, you need to specify valid credentials with *-a* and *-t* options and a
filename using *-u* option. To also register the image with ~okeanos, specify a
name using the *-r* option.

By default snf-image-creator will run a number of system preparation
preparations on the snapshot of the media and will shrink the last partition
found, before extracting the image. Both can be disabled by specifying
*--no-sysprep* and *--no-shrink* respectively.

If *--print-sysprep* is defined, then snf-image-creator will only run the OS
detection part and will output the system preparation operation that would and
would not run during image creation. This behavior is, convenient because it
allows you to see the available system preparation tasks that you can enable or
disable with *-{enable,disable}-sysprep* options when you create a new image.

Running *snf-image-creator* with *--print-sysprep* on a raw file that hosts a
debian system, we get the following output:

.. code-block:: console

   $ snf-image-creator --print-sysprep debian_desktop.img

   snf-image-creator 0.1
   =====================
   Examining source media `debian_desktop.img'... looks like an image file
   Snapshotting media source... done
   Enabling recovery proc
   Launching helper VM... done
   Inspecting Operating System... found a(n) debian system
   Mounting image... 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 I want your images to also have all normal user accounts and all mail files
removed, you can create it specifying the *--enable-sysprep* option like this:

.. code-block:: console

   $ snf-image-creator --enable-sysprep cleanup-mail,remove-user-accounts ...

Dialog-based version
====================

*snf-mkimage* receives the following options:

.. code-block:: console

   $ Usage: snf-mkimage [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

If the input media is not specified in the command line, then the user will be
asked to specify it in the first dialog box. After the input media is examined
and the program is initialized, the user is given the choice to run
*snf-mkimage* in *wizard* or *expert* mode.

Wizard mode
-----------

When *snf-mkimage* runs in *wizard* mode, the user is just asked to provide the
following basic information:

 * Name: A short name for image (ex. "Slackware")
 * Description: An one line description for the image (ex. "Slackware Linux 14.0 with KDE")
 * Account: An ~okeanos account e-mail
 * Token: A token corresponding to the account defined previously

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. In the picture below the main menu can be seen:

.. image:: /snapshots/main_menu.png

In the *Customize* submenu the user can control:

 * The system preparation operations that will run during the image creation process
 * Whether the image will be shrunk or not
 * The properties associated with the image
 * Which configuration tasks will run during image deployment

In the *Register* submenu the user can provide:

 * The credentials to login to ~okeanos
 * A pithos filename for the uploaded diskdump image
 * A name for the image to be registered to ~okeanos with

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.

Creating a new image
====================

Suppose you want to create a new Ubuntu server image. Download the installation
disk from the Internet:

.. code-block:: console

   $ wget http://ubuntureleases.tsl.gr/12.04.1/ubuntu-12.04.1-server-amd64.iso

Create a 2G sparce file to host the new system:

.. code-block:: console

   $ truncate -s 2G ubuntu_hd.raw

And install the Ubuntu system on this file:

.. code-block:: console

   $ sudo kvm -boot d -drive file=ubuntu_hd.raw,format=raw,cache=none,if=virtio \
     -cdrom ubuntu-12.04.1-server-amd64.iso

After the installation finishes, become root, activate the virtual environment
you have installed snf-image-creator in, and use *snf-mkimage* to create and
upload the image:

.. code-block:: console

   $ sudo -s
   $ source /path/to/snf-image-env/bin/activate
   $ snf-mkimage ubuntu_hd.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*.

.. image:: /snapshots/01_wizard.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.

.. image:: /snapshots/06_confirm.png

Choosing *YES* will create the image and upload it to your ~okeanos account.

Things you need to pay attention on when creating images
========================================================

Para-virtualized drivers
------------------------

~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 those drivers are built as modules, they need to be preloaded using an
initial ramdisk, otherwise the VM will not be able to boot.

In the image creation demonstration above, we initially installed the Ubuntu
system on a a hard disk (ubuntu_hd.raw) that was para-virtualized (pay
attention on the *if=virtio* option of the kvm line). The Ubuntu installer
detected that the disk was paravirtualized and made sure the appropriate
drivers will be preloaded each time the system boots. 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 then
rebuild the initial ramdisk [#f1]_ to make the virtio drivers get preloaded
during boot.

Swap partitions
---------------

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 during shrinking and will save
enough information to be able to recreate it during image deployment. This will
make your image smaller and will speed up the deployment process.

.. rubric:: Footnotes

.. [#f1] https://wiki.archlinux.org/index.php/KVM#Paravirtualized_guests_.28virtio.29