Libguestfs - Apr 2016 - Proposal to remove two virt-v2v command line options

Virt-v2v aims to convert guests without any per-guest intervention/
configuration/fiddling.

Unfortunately there are some command line options of virt-v2v which
don't meet this ideal.  Although we don't normally change the command
line of our tools, there are two options I'd like to remove (by
turning them into warnings & no-ops).

Please follow up with comments if this is going to be a problem.


Option:
   --no-trim all
   --no-trim mp[,mp...]

Description in manual:

       By default virt-v2v runs fstrim(8) to reduce the amount of data
       that needs to be copied.  This is known to break some buggy
       bootloaders causing boot failures after conversion (see for example
       https://bugzilla.redhat.com/show_bug.cgi?id=1141145#c27).

       You can use --no-trim all to disable all trimming.  Note this will
       greatly increase the amount of data that has to be copied and can
       make virt-v2v run much more slowly.

       You can also disable trimming on selected filesystems only
       (specified by a comma-separated list of their mount point(s) in the
       guest).  Typically you would use --no-trim /boot to work around the
       grub bug mentioned above.

       You can also disable trimming on partitions using the libguestfs
       naming scheme for devices, eg: --no-trim /dev/sdb2 means do not
       trim the second partition on the second block device.  Use
       virt-filesystems(1) to list filesystem names in a guest.

Discussion:

As noted in the description, we found one RHEL 5 guest which had a
buggy bootloader.  We've never been able to repeat that or find a
similarly broken guest.

When I added this option, I was suspicious that fstrim would cause
other breakage in guests.  With the popularity and widespread use of
virt-sparsify, I think that fear was unjustified.

Supporting the --no-trim option is also a pain, and it's difficult
even for users to understand what it does, so I propose we remove it.
Note this means that all guests would be fstrimmed.


Option:
   --vmtype desktop
   --vmtype server

Description in manual:

       For the -o rhev or -o vdsm targets only, specify the type of guest.
       You can set this to "desktop" or "server".  If the
option is not
       given, then a suitable default is chosen based on the detected
       guest operating system.

Discussion:

This option was inherited from old virt-v2v and it sets a single flag
in the OVF file when targetting oVirt/RHEV.  As far as I can tell this
flag affects two things in oVirt engine:

(1) Whether sound emulation is enabled for a guest ("desktop" = yes,
"server" = no).

(2) allowConsoleReconnect which disables something called "strict user
checking" when connecting to a VM console ("server" = disabled,
"desktop" = not disabled).

It is highly unlikely that a virt-v2v user understands this setting
(even I didn't understand it before now).  Note that we choose a
default from inspection data, mapping guest server-like operating
systems to "server" and the rest to "desktop".

So I propose we get rid of this option, but leave the code which
performs the default mapping from inspection data.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org