Rich Freeman <ri...@gentoo.org> wrote: > Just a few clarifications below. > > One thing this discussion is missing is any mention of BIOS / EFI. > Most of the discussion below seems most relevant to a legacy BIOS > installation. Many specialized Gentoo install docs, like mdadm+lvm, > don't really make mention of EFI, or other more recent developments. > Now that all the docs are on the wiki I'd strongly encourage anybody > with an interest to improve them. Many seasoned Gentoo users barely > reference the documentation these days and I think that is part of why > they've become a bit dated. > > A few of the topics below are somewhat controversial, particularly on > this list. I tried to stick to the facts and indicate where there is > a difference of opinion. I'd prefer not to rehash all the various > debates... > > On Sun, May 17, 2015 at 9:24 AM, Peter Humphrey <pe...@prh.myzen.co.uk> wrote: > > On Sunday 17 May 2015 12:48:58 Nuno Magalhães wrote: > > > >> (Later i want to get rid of systemd-udev and use eudev instead.) > > > > I use openrc, not systemd. It still works well and has less complication - > > and > > less typing! > > Most people using openrc are also using systemd-udev (and there is a > good chance you do too). The latter was previously named udev and > long predates what most people call systemd. Eudev is a fork of udev, > which comes from after it came under the systemd umbrella, but before > the name change and a number of changes that were controversial. I > believe they try to incorporate many of the patches from systemd-udev > but some default behaviors are different. > > In any case, I just wanted to clarify that systemd-udev is not the > "systemd" you're probably thinking of. In particular, it doesn't > replace openrc or sysvinit. Systemd-udev largely is concerned with > populating /dev, and running initialization of hardware when it is > detected, based on a configurable set of rules. > > > > >> I intend to use XFS for /. Incidentally, if i later decide to "fork > >> out" /usr (or some other subdirectory) into it's own LV, is it "just" > >> a mater of copying its contents and updating /etc/fstab? Or should i > >> just do it now and expand the LVs if later required (especially if i > >> want to use different filesystems)? > > > > I can't help you with XFS. I know that ext4 in an LV in a VG in a PV on > > RAID1 > > works reliably, even though it does look complex when I write it like that. > > As far as LVM and xfs themselves go, you can do what you propose. > > However, Gentoo QA policy is that it is expected that /usr is mounted > early in boot. Various tools can break if it is not. Typically this > is the responsibility of an initramfs, however you can also use > scripts that run early during initialization from / which mount it. > If you just stick /usr in fstab and rely on openrc to mount it for you > normally, you may or may not have problems. > > It has been a long time since I actually used such a system in this > manner with Gentoo, but the last I saw discussion on it most who used > this configuration found it usually worked fine, unless you were using > something like a bluetooth keyboard or other key system component that > required a lot of userspace tooling to make work. However, as a > matter of policy you're on your own if you choose not to mount /usr > early during boot in some way. > > The reason it is not supported is that with the rise of things like > bluetooth the list of dependencies possibly required during early boot > has grown to the point where we'd end up not even having a /usr before > long. My sense is that for the most part most maintainers tend to > respect the traditional definition of / and /usr on Gentoo, and thus > you can often get away with doing things the traditional way. > However, the policy does allow us to end debates over things like udev > rules invoking some userspace tool in /usr and such. Some packages > more strongly depend on /usr being installed in early boot, and there > have been suggestions (but nothing concrete) that Gentoo consider > supporting the /usr-move that other distros have embraced (and that > would basically get rid of /lib, /bin, and so on). > > > > > Again, legacy grub here. But if you're using an initramfs, from what I've > > seen > > you don't need to specify metadata 0.90. > > I used to use grub legacy and kernel RAID auto-assembly. As a result > I was using metadata 0.90. > > I found this configuration problematic on rare occasions. There is a > reason that mdadm changed the metadata, and why most distros don't do > it this way. (more below) > > > > > Damn. I've just checked and something has renamed my /dev/md7 to > > /dev/md127. Again. It's just too bad. I shall have to stop it when I get a > > quiet moment and reassemble it into /dev/md7. Actually, I know what caused > > it but I didn't notice at the time. > > And this was one of the configuration problems I ran into on rare > occasion. Often booting from a rescue CD or such caused something > like this to happen. > > One of the advantages of using an initramfs is that they can be a lot > smarter about finding your partitions. You can identify them by UUID > or label, and not care as much if mdadm or the kernel renames your > device nodes. > > I'd seriously take a look at dracut, though I don't know if it works > with eudev. It certainly should support openrc, and I know that it > did back when I was running openrc. It can also mount /usr for you, > and in fact it should automatically do so. It also respects your > fstab - it uses its internal logic and the kernel boot line to > initially find filesystems, but then it reads your /etc/fstab and > remounts everything as you define it there just in case something has > changed since the last time you built the initramfs/etc. You can > define your own modules for it which makes it reasonably easy to get > it to do anything at all during early boot, and it doesn't require > anything to be built static (it finds required shared objects anywhere > on the filesystem and includes them in the initramfs). It can also > give you a rescue shell if something goes wrong, and depending on your > settings you can make that rescue shell reasonably well-featured > (using either dash or bash as you prefer inside, and I imagine you > could tell it to install the other on the side). A while ago I needed > to run some btrfs tools that aren't in dracut by default and it was > trivial to tell dracut to include them, and I forced a shell on next > boot which gave me the latest tools and kernel without having to build > a rescue CD with them, and a bash shell to run them from. > > It certainly isn't necessary to use an initramfs to use Gentoo, and I > used to be among the more minimalist crowd that avoided them. > However, once I took the time to examine dracut it went from being a > blob that looked unnecessary to a tool that is often useful.
Last time I tried to use dracut with openrc, it failed, I can't remember exactly what happened, I think udev did hang, but its been a while since this happened. Dracut uses systemd internally, so maybe this is part of the problem. -- Your life is like a penny. You're going to lose it. The question is: How do you spend it? John Covici cov...@ccs.covici.com