Re: a pseudo-"clone" facility for migrating to new hardware?
On Mon, 24 Aug 2009, Joe wrote:
[regarding moving debian install from old HW to new HW ...]
> My advice would be to grit your teeth and install a completely new
> system, based on your existing packages. Then copy the data and as
> much configuration information as possible. Sorry.
that was one of my considerations. i just didn't know if there was
an existing utility to automate a lot of that. apparently not.
> Upgrading isn't a totally clean job: I upgraded from etch to lenny,
> and there were a few hiccups.
that part of it will be happening later today. as i've mentioned
before, i'm upgrading to lenny on the *old* server first, so the
migration will be as easy as possible. actually, i'm upgrading in
several phases -- safe upgrade, wait for things to settle and tweak as
necessary, followed by a dist-upgrade ... repeat until done.
what's been done so far on the old server, one step at a time,
debugging and tweaking all the while:
* upgrade sarge
* safe upgrade to etch
* dist upgrade to etch
* upgrade etch kernel to 2.6.18, discover it's broken
* upgrade etch hernel to 2.6.24, still broken
* upgrade etch kernel to 2.6.26, working again
and that's the state of the old server as we speak. the last two
phases:
* switch /etc/apt/sources.list to "stable", safe upgrade, tweak
* dist upgrade to lenny, tweak, beer
at which point i'm as up to date as i'm going to get on the old
server, and it will be time to migrate it over to the new HW.
> If you use exim4, and you haven't upgraded it yet, the configuration
> model is a bit different, and if you tell it to use the existing
> configuration, it will die horribly...
no exim. apparently, mercifully. :-)
> Apache/php is also very slightly different, and I still have a
> couple of minor quirks I haven't tracked down yet. Unavoidable
> whichever way you go.
i figured the apache upgrade would have some issues, so is there any
problem with just sticking with apache1 for the time being? that's
what's running on the etch system now, should it still run nicely on
lenny until i know exactly what the upgrade process is to move to
apache2?
> As you're also changing hardware and moving to LVM, I'd think there
> are enough potential gotchas to do a clean install. That way, you
> also get to bring it up in parallel, and can fix some problems with
> reference to a running system. I was in almost exactly the same
> position, having upgraded old hardware to lenny prior to moving, and
> the experience of the upgrade led me to do a clean install and data
> migration, which wasn't difficult.
hmmmmmm ... i'm thinking that i could cheat a bit and, since the new
hard drives are massively larger than the single existing one, i could
just set up another single root filesystem on the new first drive and
copy everything over, then switch to LVM sometime down the road by
manually formatting the (unused) second drive, copying over the entire
install, and switching drives. that would have the advantage of being
able to *exactly* reproduce the running system, without having to load
it into a previous debian install. or is that overkill?
in any event, i have more than enough room to migrate onto a single
drive, and use the second drive to slowly and carefully duplicate that
install until i'm ready to switch to what i want long-term.
> There is also the point that an upgraded system is not identical to
> a clean install. Some things will end up slightly different,
> particularly configurations, as some shortcuts will clearly be
> possible if there's no existing system to stay compatible with. My
> etch was already an upgrade from sarge, which may have complicated
> things.
deja vu. :-) what i'm going to do later today is peruse the
installed packages and see if there are any that are obviously
redundant or obsolete, just so i can strip the running system down as
much as possible to simplify things and avoid interactions and side
effects.
> I'm sure it is possible to just keep upgrading, and that a number of
> people will jump in and tell me they have done this from potato or
> earlier, but I run a live mail server with no backup and I really
> don't want it to be down for more than a couple of hours. Parallel
> running was very attractive.
i'll bet it was. thanks for the advice.
rday
--
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Robert P. J. Day Waterloo, Ontario, CANADA
Linux Consulting, Training and Annoying Kernel Pedantry.
Web page: http://crashcourse.ca
Twitter: http://twitter.com/rpjday
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