Bug#797131: udev kernel check during Wheezy->Jessie upgrade should happen earlier

[Andy Valencia]

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> I do not think that there is anything else that udev can do, since the 
> check is done in udev.preinst.

I hope you might consider talking to the apt folks.  At least under a
dist-upgrade it seems like this failure could be detected sooner rather
than later.  It's not like udev is some minor package they've never
heard of.  It is very desirable that an attempted upgrade not result in
a half-upgraded (and thus fully broken) system.

> Also, I suspect that you were running a custom kernel, so this would not 
> happen during normal upgrades.

Well, perhaps custom in the sense that the system maker configured the
kernel--it isn't from a Debian build farm.  In the armhf world vendors
seem to try and trim back "unneeded" kernel features.

BTW, in the Jessie release notes:

    5.7. Required kernel config options for Jessie

       [Note] Note

       This section is only for people who compile their own kernel. If you use the kernels
       compiled by Debian, you can disregard this section.

       The following kernel configuration options are now either required or recommended for Jessie
       (in addition to existing ones from previous releases):

    # Required for udev
    CONFIG_DEVTMPFS=y

    (... other needs from other packages)

If you do nothing else, please consider adding documentation of
the need for:

    - inotify(2)            (CONFIG_INOTIFY_USER)
    - signalfd(2)           (CONFIG_SIGNALFD)
    - open_by_handle_at(2)  (CONFIG_FHANDLE)
    - timerfd_create(2)     (CONFIG_TIMERFD)
    - epoll_create(2)       (CONFIG_EPOLL)

to the release notes.  I would've checked and taken care of the kernel
configuration if it had been noted in the release notes.

Thanks...
Andy Valencia