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