[bug #32931] LVM write support, patch included

[Valentin Hilbig]

Follow-up Comment #2, bug #32931 (project grub):

Thanks, good point, I missed that completely.

Lession learned, having write support in LVM is probably evil.  OTOH not
having LVM write support is a complete desaster (see below).  So I hope a
suitable fix for the time being (until somebody fixes it 101%) can be to allow
users to enable write support if they really want it.

In the new patch (lvm-write.2.patch) this is controlled by environment
variable "lvm_write_enabled".  It increases lvm.mod by 560 bytes.

Example:

Boot grub
c
insmod lvm 
set prefix=(VGNAME-boot)/grub 
load_env 
set saved_entry=2 
save_env saved_entry 
# This fails now
set lvm_write_enabled=true
save_env saved_enty lvm_write_enabled
# now worked
reboot

Some rationale on this patch:

At my side Linux is installed into LVM and the GRUB config must be on LVM too.
 My setup is Multiboot and Windows breaks if GRUB does not automatically boot
into it after hibernation.

So a not working save_env is a complete showstopper at my side.  And I don't
think I am alone with this!

As I cannot provide a separate /boot partition in my environment either,
enabling LVM writes are the only way to get my setup working here.

I hope, to disable writes by default and enable them on user's request is the
best of both worlds for now.

The downside is that it does not work perfectly on mirrored LVM.  However I
would say that LVM mirror support is extremely dangerous anyway, so the
trouble GRUB adds does not count much.  My recommendation on mirroring is: Use
MD instead, it just works.

Note:

The patch does not need to make it into dist soon, as you can see,  patching
yourself is not much effort.

(file #23033)
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Additional Item Attachment:

File name: lvm-write.2.patch              Size:3 KB


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