Date: Sun, 28 Jul 2013 21:55:43 +0200 (CEST) From: Conny Andersson <ataraxi@telia.com> To: Ian Smith <smithi@nimnet.asn.au> Cc: freebsd-questions@freebsd.org Subject: Re: FreeBSD slices and the Boot Manager Message-ID: <alpine.BSF.2.00.1307282131570.1188@alice.nodomain.nowhere> In-Reply-To: <20130729013637.M32053@sola.nimnet.asn.au> References: <mailman.57.1375012801.93006.freebsd-questions@freebsd.org> <20130729013637.M32053@sola.nimnet.asn.au>
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Hi Ian, Thank you for all of your advices regarding my questions. I have been using FreeBSD for more than ten years, but I never heard of sade (sysadmins disk editor). That is one of the joyful things with running FreeBSD/Unix; there is always something earlier unheard of to explore. And, there is always more than one way to approach a problem. Thank you Ian, Conny > On Mon, 29 Jul 2013, Ian Smith wrote: > In freebsd-questions Digest, Vol 477, Issue 8, Message: 10 > On Sat, 27 Jul 2013 19:39:30 +0200 (CEST) Conny Andersson <ataraxi@telia.com> wrote: > > Hi, > > > > I have a workstation with two factory installed hard disks. The first disk, > > ada0, is occupied by a Windows 7 Pro OS (mainly kept for the three year > > warranty of the workstation as Dell techs mostly speak the Microsoft > > language). > > Yes, best humour adherents of the Almighty Bill - keeps them sweet. > > > Instead I have configured the BIOS to boot from the MBR on the second disk > > as I most of the time (99%) use FreeBSD. The MBR on ada1 was installed with > > sysinstall's option "Install the FreeBSD Boot Manager", when I installed > > the FreeBSD 8.3-RELEASE. > > Right. sysinstall(8) - or at least the fdisk and bsdlabel modules that > constitute sade(8) - remains the only safe and sane way to handle MBR > disks. bsdinstall seems fine for GPT, but its paradigm doesn't play so > well with trying to do the sorts of manipulations you're talking about > here. Why noone's tried to update sade(8) for GPT I don't understand; > it's a far better, more forgiving interface, in my old-fashioned? view. > > > (The latest BIOS version 2.4.0 for Dell T1500 does not support > > UEFI/GPT/GUID.) > > > > The second disk ada1, now has three FreeBSD slices: > > > > 1) ada1s1 with FreeBSD 8.1-RELEASE > > > > 2) ada1s2 with FreeBSD 8.2-RELEASE > > > > 3) ada1s3 with FreeBSD 8.3-RELEASE > > > > I want to install the new FreeBSD 8.4-RELEASE on ada1s1 by overwriting the > > now existing two first slices. This means that ada1s3, must become ada1s2 > > instead. Is this possible to do? > > Yes and no. Using sysinstall|sade on my 9.1 laptop -- without setting > sysctl kern.geom.debugflags=16 so it can't write any inadvertent changes > to my disk :) -- in the fdisk screen you can delete the first two slices > freeing their space for a new slice (or two) and you can then allocate > s1 ok, but the existing s3 is still called s3. Would that be a problem? > > If you only created one slice there you'd have s1 and s3, with s2 and s4 > marked as empty in the MBR shown by fdisk(8). MBR slice order need not > follow disk allocations, eg s4 might point to an earlier disk region. > > sysinstall|sade has undo options for both fdisk and bsdlabel modules; > it's easy to play with, no chance of damage - even with foot-shooting > flag set, unless/until you commit to changes. If in doubt hit escape > until it backs right out, nothing will be written. > > > A very important question is if sysinstall's option "Install the FreeBSD > > Boot Manager" detects that I have a FreeBSD 8.3 and detect it as slice 2 on > > disk 1? So it becomes a boot option when I am rebooting? (Maybe the slice > > may come up as ad6s2, because AHCI in FreeBSD 8.4 isn't enabled at the time > > of the install.) > > If you're running 8.4 sysinstall as init, ie booted into the installer, > and you've told it to install to s1, then it should set s1 as the active > partition in the disk table and in boot0cfg's active slice table. I've > never tried it with a second disk so I can't confirm that will all play > nice, but you seem to have installed 3 versions ok before :) > > If not, you can run boot0cfg(8) anytime to set the active slice etc, so > that shouldn't be a worry. Likely need to set debugflags=16 to do that > on a running system also .. don't forget to set them back to 0 later! > > (For anyone) still nervous about sade for setting up MBR disks, play > with a spare memstick, setup a couple of slices, boot0cfg etc, allocate > and delete slices and partitions. Jordan got that together >15years ago > so noone would ever need to do those icky slice/partition maths again. > My theory: few have been brave enough to dare mess with $deity's work, > though it just needs some updates for modern realities, not abandonment. > > [ Polytropon, it's not 'obsolete' at all; still in 9 anyway. It'll be > obsolete when there are no more MBR-only systems in use - say 7 years - > OR when bsdinstall incorporates all the missing good sade(8) features, > which requires it making a clear distinction between GPT and MBR and > working accordingly, including cleaning up GPT stuff if MBR chosen. At > 9.1-R anyway, it doesn't do it so well for MBR. Try installing over an > existing desired slice partitioning, newfs'ing everything EXCEPT your > valuable /home partition. Not for beginners, yet simple in sade(8) ] > > > If the answer to these questions is yes, then the next two questions arise. > > > > Can I mount ada1s2a (FreeBSD 8.3) from the newly installed FreeBSD 8.4 and > > edit my FreeBSD's 8.3-R /etc/fstab according to the new disk layout, and > > occasionally run FreeBSD 8.3 without problems? Or do I have to do more to > > get it to work? > > Except it likely will still be called ada1s3a, it should be no problem. > Once boot0cfg(8) is working right, you can boot from any bootable slice; > it 'knows' but doesn't care what (if any) OS is on any other slices. > > > The idea behind this kind of 'reverse' disk layout of mine is to have > > FreeBSD 8.4 as my new default OS. And have FreeBSD 8.3 untouched for > > configuring FreeBSD 8.4 and booting into it when ever needed. If I can do > > this as described above, I will have plenty of space on the disk for the > > future and a new FreeBSD release. > > Sure. Another option would be a much smaller new s2 after the bigger s1 > as a 'transit lounge' between slices, I use such for config backups etc. > > Speaking of which, given that you're all safely backed up, nothing can > go wrong, right? :) > > cheers, Ian
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