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Old 04-14-2012, 01:44 AM
 
Default Another plan for /usr and udev-181

Dale as inspired me to finally do something about udev-181. Can't
keep my finger in the dike forever. But I have been thinking of a
different approach.

What annoys me the most about this forced change is that I like the
old unix style of a single minimal base partition for booting, and
being able to manage all the other partitions while unmounted in
single user mode. In my case, /usr is an LVM partition precisely
because I want to sit in single user mode while resizing it (it seems
to keep on growing ...). However, progress marches on, removable
media are taking over, and it's best to not be a luddite all the time.

So I think I will try the initramfs approach of mounting /usr during
boot. I don't think this will make growing /usr any easier; single
user mode won't umount it. But it does preserve the option of
reverting to the old fashioned way if sanity prevails and udev-181 is
found unnecessary.

1. Configure the next kernel with the necessary initramfs flags, then
have two grub entries for the same kernel: one with the initramfs
and one without. Initially I will make the initramfs do something
innocuous, and leave /usr as a separate /etc/fstab entry mounted
in the old fashioned way.

2. Make sure boot works the old fashioned way, without initramfs.

3. Make sure boot works the new fangled way, with initramfs.

4. Create some temporary lvm partition and make sure the new fangled
initramfs mounts it during boot without an /etc/fstab entry.

5. Remove /usr from /etc/fstab and put it in the initramfs, and make
sure that boot works.

6. Merge udev-181 and whatever else is needed.

7. Cross my fingers, sacrifice a virtual goat, and try a reboot.

Somewhere between 6 and 7 is the worst part; no simple way to revert
and retry. Everything up til then should require no more than a
simple /etc/fstab edit.

Is there any way to add more steps between 6 and 7 to allow more
reversability?

Have I left out any steps, between 6 and 7 or anywhere else?

--
... _._. ._ ._. . _._. ._. ___ .__ ._. . .__. ._ .. ._.
Felix Finch: scarecrow repairman & rocket surgeon / felix@crowfix.com
GPG = E987 4493 C860 246C 3B1E 6477 7838 76E9 182E 8151 ITAR license #4933
I've found a solution to Fermat's Last Theorem but I see I've run out of room o
 
Old 04-14-2012, 04:03 AM
Canek Peláez Valdés
 
Default Another plan for /usr and udev-181

On Fri, Apr 13, 2012 at 8:44 PM, <felix@crowfix.com> wrote:
> Dale as inspired me to finally do something about udev-181. *Can't
> keep my finger in the dike forever. *But I have been thinking of a
> different approach.
>
> What annoys me the most about this forced change is that I like the
> old unix style of a single minimal base partition for booting, and
> being able to manage all the other partitions while unmounted in
> single user mode. *In my case, /usr is an LVM partition precisely
> because I want to sit in single user mode while resizing it (it seems
> to keep on growing ...). *However, progress marches on, removable
> media are taking over, and it's best to not be a luddite all the time.
>
> So I think I will try the initramfs approach of mounting /usr during
> boot. *I don't think this will make growing /usr any easier; single
> user mode won't umount it.

Mmmh. You don't need single user mode anymore with an initramfs (at
least with dracut). From dracut.cmdline(7):

rd.break={cmdline|pre-udev|pre-trigger|initqueue|pre-mount|mount|pre-pivot}
drop to a shell on defined breakpoint

You add that to your kernel command line in GRUB/GRUB2, and it drops
you tou a shell before doing the mount (pre-mount). Then you only need
to put the necessary LVM tools in the initramfs; since my LVM
installation is 3.13 MB, it sounds like a reasonable feature. Or you
can have a "fat" initramfs (with another GRUB entry) for resizing LVM
volumes, and a "slim" normal initramfs with its corresponding GRUB
entry.

Other way in which (IMHO) an initramfs is a better option that
stuffing everything and the kitchen sink on /.

My 0.02 ${CURRENCY}.

Regards.
--
Canek Peláez Valdés
Posgrado en Ciencia e Ingeniería de la Computación
Universidad Nacional Autónoma de México
 
Old 04-14-2012, 05:12 AM
 
Default Another plan for /usr and udev-181

On Fri, Apr 13, 2012 at 11:03:43PM -0500, Canek Pel??ez Vald??s wrote:

> Mmmh. You don't need single user mode anymore with an initramfs (at
> least with dracut). From dracut.cmdline(7):
>
> rd.break={cmdline|pre-udev|pre-trigger|initqueue|pre-mount|mount|pre-pivot}
> drop to a shell on defined breakpoint
>
> You add that to your kernel command line in GRUB/GRUB2, and it drops
> you tou a shell before doing the mount (pre-mount). Then you only need
> to put the necessary LVM tools in the initramfs; since my LVM
> installation is 3.13 MB, it sounds like a reasonable feature. Or you
> can have a "fat" initramfs (with another GRUB entry) for resizing LVM
> volumes, and a "slim" normal initramfs with its corresponding GRUB
> entry.
>
> Other way in which (IMHO) an initramfs is a better option that
> stuffing everything and the kitchen sink on /.

Interesting stuff. I see I had better get familiar with dracut and
maybe try some things out.

Back in the stone age, there was no kitchen sink to put in /bin :-)

--
... _._. ._ ._. . _._. ._. ___ .__ ._. . .__. ._ .. ._.
Felix Finch: scarecrow repairman & rocket surgeon / felix@crowfix.com
GPG = E987 4493 C860 246C 3B1E 6477 7838 76E9 182E 8151 ITAR license #4933
I've found a solution to Fermat's Last Theorem but I see I've run out of room o
 
Old 04-14-2012, 06:35 AM
Neil Bothwick
 
Default Another plan for /usr and udev-181

On Fri, 13 Apr 2012 18:44:37 -0700, felix@crowfix.com wrote:

> What annoys me the most about this forced change is that I like the
> old unix style of a single minimal base partition for booting, and
> being able to manage all the other partitions while unmounted in
> single user mode. In my case, /usr is an LVM partition precisely
> because I want to sit in single user mode while resizing it (it seems
> to keep on growing ...).

It's been safe to increase the size of mounted filesystems for years. But
if you can enlarge /usr while using it, you can do the same for/. So if
that's your only reason for a separate /usr...


--
Neil Bothwick

In a classified ad: "Tired of cleaning yourself? Let me do it."
 
Old 04-14-2012, 06:39 AM
Neil Bothwick
 
Default Another plan for /usr and udev-181

On Fri, 13 Apr 2012 18:44:37 -0700, felix@crowfix.com wrote:

> 6. Merge udev-181 and whatever else is needed.
>
> 7. Cross my fingers, sacrifice a virtual goat, and try a reboot.
>
> Somewhere between 6 and 7 is the worst part; no simple way to revert
> and retry. Everything up til then should require no more than a
> simple /etc/fstab edit.
>
> Is there any way to add more steps between 6 and 7 to allow more
> reversability?

Create a binary package for the old udev, then you can boot from a live
CD, chroot in and emerge the old version. If the breakage is too bad for
even that, you can even untar the package into the root directory.


--
Neil Bothwick

Of course it's not your day,
 
Old 04-14-2012, 07:13 AM
Dan Johansson
 
Default Another plan for /usr and udev-181

On Friday 13 April 2012 18.44:37 felix@crowfix.com wrote:
> 1. Configure the next kernel with the necessary initramfs flags, then
> have two grub entries for the same kernel: one with the initramfs
> and one without. Initially I will make the initramfs do something
> innocuous, and leave /usr as a separate /etc/fstab entry mounted
> in the old fashioned way.
>
> 2. Make sure boot works the old fashioned way, without initramfs.
>
> 3. Make sure boot works the new fangled way, with initramfs.
>
> 4. Create some temporary lvm partition and make sure the new fangled
> initramfs mounts it during boot without an /etc/fstab entry.
>
> 5. Remove /usr from /etc/fstab and put it in the initramfs, and make
> sure that boot works.
>
> 6. Merge udev-181 and whatever else is needed.
>
> 7. Cross my fingers, sacrifice a virtual goat, and try a reboot.
>
> Somewhere between 6 and 7 is the worst part; no simple way to revert
> and retry. Everything up til then should require no more than a
> simple /etc/fstab edit.
>
> Is there any way to add more steps between 6 and 7 to allow more
> reversability?
>
> Have I left out any steps, between 6 and 7 or anywhere else?

I have done also something like this.
I still have /usr in fstab (with the noauto option) just for reference.
The only thing (that I have noticed yet) is that the /etc/init.d/lvm fails due to the fact that LVM is already started (in initramfs).

--
Dan Johansson, <http://www.dmj.nu>
************************************************** *
This message is printed on 100% recycled electrons!
************************************************** *
 
Old 04-14-2012, 10:35 AM
 
Default Another plan for /usr and udev-181

On Sat, 14 Apr 2012 07:35:52 +0100
Neil Bothwick <neil@digimed.co.uk> wrote:

> On Fri, 13 Apr 2012 18:44:37 -0700, felix@crowfix.com wrote:
>
> > What annoys me the most about this forced change is that I like the
> > old unix style of a single minimal base partition for booting, and
> > being able to manage all the other partitions while unmounted in
> > single user mode. In my case, /usr is an LVM partition precisely
> > because I want to sit in single user mode while resizing it (it
> > seems to keep on growing ...).
>
> It's been safe to increase the size of mounted filesystems for years.
> But if you can enlarge /usr while using it, you can do the same for/.
> So if that's your only reason for a separate /usr...
>
>

/ on LVM is officially not "supported" (in the sense there are no
official documentation about it) in Gentoo, and is discouraged in the
Gentoo LVM installation guide. Has been the case since the beginning,
although there are unofficial wiki and mailinglist/forum posts about
it. Of course, / on LVM would require an initrd.

That's one reason why many of us using LVM keeps /usr on LVM while / as
a physical partition. This allows for maximum flexibility, and is a
supported "legacy" config without an initrd. I may add many of us had
bad experience with initrd from binary distros rendering system
unbootable (I've been there with Debian and Arch --- back in 2003 or
so you cannot uninstall currently running kernel & initrd after
installing a new kernel, or else the next time your newly installed
kernel won't boot. Also sometimes the newly installed kernel+initrd
won't boot, and neither would the old kernel+initrd...).

Of course, now that separate /usr requires an initrd, one might as well
put / on LVM and let busybox in initrd handles the case when LVM goes
wrong (urgh!). Still, Gentoo doesn't officially support this
configuration.

--

Kerwin
 
Old 04-14-2012, 01:32 PM
 
Default Another plan for /usr and udev-181

On Sat, Apr 14, 2012 at 06:35:45PM +0800, kwkhui@hkbn.net wrote:
> On Sat, 14 Apr 2012 07:35:52 +0100
> Neil Bothwick <neil@digimed.co.uk> wrote:
>
> > On Fri, 13 Apr 2012 18:44:37 -0700, felix@crowfix.com wrote:
> >
> > > What annoys me the most about this forced change is that I like the
> > > old unix style of a single minimal base partition for booting, and
> > > being able to manage all the other partitions while unmounted in
> > > single user mode. In my case, /usr is an LVM partition precisely
> > > because I want to sit in single user mode while resizing it (it
> > > seems to keep on growing ...).
> >
> > It's been safe to increase the size of mounted filesystems for years.
> > But if you can enlarge /usr while using it, you can do the same for/.
> > So if that's your only reason for a separate /usr...
> >
> >
>
> / on LVM is officially not "supported" (in the sense there are no
> official documentation about it) in Gentoo, and is discouraged in the
> Gentoo LVM installation guide. Has been the case since the beginning,
> although there are unofficial wiki and mailinglist/forum posts about
> it. Of course, / on LVM would require an initrd.
>
> That's one reason why many of us using LVM keeps /usr on LVM while / as
> a physical partition. This allows for maximum flexibility, and is a
> supported "legacy" config without an initrd.

That's my position :-) and half-hoping all this udev-181 needing /usr
stuff will disappear and I can go back ...

--
... _._. ._ ._. . _._. ._. ___ .__ ._. . .__. ._ .. ._.
Felix Finch: scarecrow repairman & rocket surgeon / felix@crowfix.com
GPG = E987 4493 C860 246C 3B1E 6477 7838 76E9 182E 8151 ITAR license #4933
I've found a solution to Fermat's Last Theorem but I see I've run out of room o
 
Old 04-14-2012, 01:35 PM
 
Default Another plan for /usr and udev-181

On Sat, Apr 14, 2012 at 09:13:09AM +0200, Dan Johansson wrote:

> I have done also something like this.
> I still have /usr in fstab (with the noauto option) just for reference.

Good idea, better than commenting it out.

> The only thing (that I have noticed yet) is that the /etc/init.d/lvm fails due to the fact that LVM is already started (in initramfs).

I suppose this is just a harmless error message, instead of getting so
confused it makes a mess of things.

--
... _._. ._ ._. . _._. ._. ___ .__ ._. . .__. ._ .. ._.
Felix Finch: scarecrow repairman & rocket surgeon / felix@crowfix.com
GPG = E987 4493 C860 246C 3B1E 6477 7838 76E9 182E 8151 ITAR license #4933
I've found a solution to Fermat's Last Theorem but I see I've run out of room o
 

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