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Re: /usr/lib vs /usr/libexec

On Tuesday 10 May 2005 10:36, Goswin von Brederlow 
<brederlo@informatik.uni-tuebingen.de> wrote:
> - / can't be on lvm, raid0, raid5, reiserfs, xfs without causing
> problems for /boot.

I believe that there are LILO patches for /boot on LVM.  There's no reason why 
GRUB and other boot loaders couldn't be updated in the same manner.  The most 
obvious solution is to have the LV containing /boot being marked in the LVM 
setup as contiguous.  Then the boot loader merely has to use a different 
method of finding the first block.

ReiserFS has been supported for /boot for ages.  When I took over maintenance 
of LILO it was initially to get the ReiserFS patches included.

RAID-0 could be supported by boot loaders.  The only real complication is the 
need to correctly identify two boot disks (correctly identifying one is 
enough pain as anyone who has worked with boot loader code knows well).  In 
fact I'm reasonably sure that the only reason for not having support for 
RAID-0 in boot loaders is the fact that it's so painful to identify two disks 
correctly.  When you have N disks the difficulty (for programmer and for 
sys-admin) will be of order N*(N-1) instead of being of order N.

But generally the best solution to such problems is to have a separate 
partition for /boot.  Red Hat defaults to an LVM install (including LVM root) 
with a regular 100M partition for /boot, that works well.

> - a larger FS has more chance of failing so you risk having a fully
> broken system more often

I doubt that.

I think that a FS that is written less has less chance of failing, which is an 
extra reason for having /var and /home on different file systems to /.  If 
you have /var and /home on separate partitions then / should not get many 
writes and should have little chance of corruption regardless of size.

> - /usr can be easily network (shared accross the same arch) mounted
> while / (due to /etc) can't

Why is this desirable in the days of large disks?  There is no machine for 
which I am responsible which has a disk space issue other than my laptop.  
None of my machines has /usr taking any significant portion of the disk 

> - / needs functioning device nodes on it while usr can be mounted nodev

The current Fedora setup of having an initrd create device nodes on a tmpfs is 
working quite well and could be copied for Debian.

> - a small / can be replicated across many disks to ensure the system
> always comes up and e.g. at least send an email to the admin. / can
> even be an initrd

How big can an initrd be?  The default is 4M which isn't going to do well 
for /.

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