| 1 |
Hello, Rich. |
| 2 |
|
| 3 |
On Tue, Jan 29, 2019 at 12:58:38 -0500, Rich Freeman wrote: |
| 4 |
> On Tue, Jan 29, 2019 at 11:48 AM Alan Mackenzie <acm@×××.de> wrote: |
| 5 |
|
| 6 |
> > On Tue, Jan 29, 2019 at 09:32:19 -0700, Grant Taylor wrote: |
| 7 |
> > > On 01/29/2019 09:08 AM, Peter Humphrey wrote: |
| 8 |
> > > > I'd rather not have to create an initramfs if I can avoid it. Would it |
| 9 |
> > > > be sensible to start the raid volume by putting an mdadm --assemble |
| 10 |
> > > > command into, say, /etc/local.d/raid.start? The machine doesn't boot |
| 11 |
> > > > from /dev/md0. |
| 12 |
|
| 13 |
|
| 14 |
> > For this, the kernel needs to be able to assemble the drives into the |
| 15 |
> > raid at booting up time, and for that you need version 0.90 metadata. |
| 16 |
> > (Or, at least, you did back in 2017.) |
| 17 |
|
| 18 |
|
| 19 |
> Can't say I've tried it recently, but I'd be shocked if it changed |
| 20 |
> much. The linux kernel guys generally consider this somewhat |
| 21 |
> deprecated behavior, and prefer that users use an initramfs for this |
| 22 |
> sort of thing. It is exactly the sort of problem an initramfs was |
| 23 |
> created to fix. |
| 24 |
|
| 25 |
An initramfs is conceptually so ugly that I view it as a workaround, not |
| 26 |
a fix, to whatever problem it's applied to. It would surely be a bug if |
| 27 |
the kernel were capable of manipulating RAIDs, but not of initialising |
| 28 |
and mounting them. |
| 29 |
|
| 30 |
> Honestly, I'd just bite the bullet and use dracut if you want your OS |
| 31 |
> on RAID/etc. It is basically a one-liner at this point to install and |
| 32 |
> a relatively small tweak to your GRUB config (automatic if using |
| 33 |
> mkconfig). Dracut will respect your mdadm.conf, and just about all |
| 34 |
> your other config info in /etc. The only gotcha is rebuilding your |
| 35 |
> initramfs if it drastically changes (but, drastically changing your |
| 36 |
> root filesystem is something that requires care anyway). |
| 37 |
|
| 38 |
Well, at the moment my system's not broken, hence doesn't need fixing. |
| 39 |
Last time I looked at Dracut, it would only work in a kernel built with |
| 40 |
modules enabled, ruling out my setup. |
| 41 |
|
| 42 |
Also, without putting in a LOT of time and study, dracut is a massive, |
| 43 |
opaque mystery. I've got a pretty good mental picture of how my system |
| 44 |
works, and introducing an initramfs would degrade that picture |
| 45 |
enormously. That means if any problems happened with the initramfs, I'd |
| 46 |
be faced with many days study to get to grips with it. |
| 47 |
|
| 48 |
> But, if you're not using an initramfs you can get the kernel to handle |
| 49 |
> this. Just don't be surprised when it changes your device name or |
| 50 |
> whatever. |
| 51 |
|
| 52 |
The kernel seems to leave it alone. Any Gentoo installation CD I've |
| 53 |
used has corrupted the setup, changing all the names to /dev/md127, |
| 54 |
/dev/md126, ...., leaving the victim PC unbootable. Hence my root |
| 55 |
partition is /dev/md127, despite me originally creating it as something |
| 56 |
like /dev/md4. |
| 57 |
|
| 58 |
> -- |
| 59 |
> Rich |
| 60 |
|
| 61 |
-- |
| 62 |
Alan Mackenzie (Nuremberg, Germany). |
Archives