[Bug 1423796] Re: Unable to mount lvmcache root device at boot time
Astara
ubuntu at tlinx.org
Sun Nov 27 23:16:13 UTC 2016
@George:
George Moutsopoulos (gmoutso) wrote on 2015-04-29:
> OK, I managed! I had to add more modules
>
> sudo echo "dm_cache" >> /etc/initramfs-tools/modules
> sudo echo "dm_cache_mq" >> /etc/initramfs-tools/modules
> sudo echo "dm_persistent_data" >> /etc/initramfs-tools/modules
> sudo echo "dm_bufio" >> /etc/initramfs-tools/module
---
Not exactly related to the original bug, but wanted to address a boo-boo in the above.
sudo echo "string" won't use root's access/permissions to write to the files when using the shell-redirection operators '>' or '>>'. sudo will execute 'echo' with root privs, and that will echo "dm_cache" (et al.), however, that output is redirected by the *SHELL* (running as
"whoever is running the shell") -- usually the user.
To get around this problem (and not saying there might not be any easier ways, as this seemed a bit roundabout to get what I wanted (have root write the output to "wherever"), I used
"dd", as in:
echo "dm_cache"|sudo dd of=destination status=none
or to append:
echo "dm_cache"|sudo dd status=none oflag=append conv=notrunc of=/etc
/initramfs-tools/modules
or to do all at once:
(echo dm_cache
echo dm_cache_mq
echo dm_persistent_data
echo dm_bufio)|sudo dd status=none oflag=append conv=notrunc of=/initramfs-tools/modules
I wanted to write a single "char" to a file in /proc/sys/vm
(drop_caches).
Perhaps needless to say, I put it in a script file to save on typing.
:-)
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https://bugs.launchpad.net/bugs/1423796
Title:
Unable to mount lvmcache root device at boot time
Status in initramfs-tools package in Ubuntu:
Confirmed
Status in linux package in Ubuntu:
Confirmed
Status in lvm2 package in Ubuntu:
Confirmed
Bug description:
I'm experimenting with Vivid Vervet on a virtual machine and tried a
new LVM feature, lvmcache. I made a cache for the root file system,
rebuilt the initrd and rebooted the VM.
At boot time, the system failed to activate the root LV. After some
investigation, I found out, it's because the initrd is missing some
essential stuff needed for activating a cached LV.
The initrd was missing the dm-cache module. I regenerated the initrd
with explicitly listing dm-cache in /etc/initramfs-tools/modules, but
the system still can't boot up, because now it is missing the
/usr/sbin/cache_check utility.
As SSDs are becoming more and more common, I think it will be common
to use them as cache for root file systems, thus it is mandatory to
make sure that an initrd can mount an lvmcached root device when
necessary, preferably without /etc/initramfs-tools/modules and other
manual initrd hacking.
System details:
Linux lvmvm 3.18.0-13-generic #14-Ubuntu SMP Fri Feb 6 09:55:14 UTC
2015 x86_64 x86_64 x86_64 GNU/Linux
Distributor ID: Ubuntu
Description: Ubuntu Vivid Vervet (development branch)
Release: 15.04
Codename: vivid
LVM version: 2.02.111(2) (2014-09-01)
Library version: 1.02.90 (2014-09-01)
Driver version: 4.28.0
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