process checkpoint restore facility now in DragonFly BSD

[Matthew Dillon]

    If you guys are interested in the checkpointing code, now is the time
    to port it.  And maybe someone could donate the last little bit required
    to make it reasonably secure when used by a non-root user.  That bit being
    to have the kernel record the file handles and creds in a root-owned file
    separately from the file handles recorded in the checkpoint file so
    a user-checkpointed program's file handles can be validated on restore
    rather then just using them blindly.

    Its kind of a cop-out to say it isn't perfect and thus one should wait...
    the issue with checkpointing is that it *isn't* possible to make it
    perfect, no matter how much work you put into it.  At least not if your
    goal is something that can survive a reboot.  There always needs to be
    some level of checkpoint-aware interaction with a program to make it
    work well.  This last little bit we implemented with signals.  The
    checkpoint API in DragonFly is considered stable and apart from the file
    handle security issue I do not envision any further development on the
    basic mechanism.  Certainly nothing need to be rewritten.

    The checkpointing we have done has nothing at all to do with saving the
    entire system state for some sort of low-power mode on a machine.
    That would be a totally different beast and the two should not be 
    confused.

    Of course, I have a wish list a mile long.  But that's just me.  If you
    wait for the whole enchillada you'll never have checkpointing.

					    -Matt