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Re: Access ZFS pool in debian 10 single user mode



On Wed, 2 Sep 2020 at 22:06, Dan Ritter <dsr@randomstring.org> wrote:

James Allsopp wrote:
Hi,
Just trying to move var to a zfs partition. Rebooted into recovery mode,
but could access the zfs pool. I tried to modprobe zfs, but still
nothing.
Is there something else I should be doing?


Does your recovery mode have the zfs kernel modules and zfsutil?

Without it, you'll never mount things.

On 2020-09-03 01:34, James Allsopp wrote:
> This is just debian grub recovery mode so on the same machine, so hopefully
> zfsutil will be there. Looked at this;
> zfs                  4214784  9
> zunicode              335872  1 zfs
> zlua                  172032  1 zfs
> zavl                   16384  1 zfs
> icp                   331776  1 zfs
> zcommon                98304  2 zfs,icp
> znvpair                90112  2 zfs,zcommon
> spl                   122880  5 zfs,icp,znvpair,zcommon,zavl
>
> So if I just modprobe those from the column on the left, it should work?


[Top posted reply moved to bottom.]


I am unable to find a canonical Debian policy on the subject of posting style for Debian mailing lists:

https://www.debian.org/MailingLists/#codeofconduct

https://www.debian.org/code_of_conduct


Most readers of this list seem to prefer attributed, indented, trimmed, interleaved posting style, but this response is bottom posted:

https://en.wikipedia.org/wiki/Posting_style


This is a popular essay on the subject:

http://www.catb.org/~esr/faqs/smart-questions.html


[Back to the technical discussion.]


I appears that Debian single-user mode does not load the kernel modules you need. I assume this is by design, so that you can boot the system when you have a bad module.


Loading modules by hand in single user mode might work, but there is the chicken-and-egg question starting with "can you boot into single user mode without a /var filesystem?".


I find it is very useful to have a complete Debian installation on a USB flash drive with all the software I need to do system administration on Debian machines. Using such, I could easily move /var to ZFS. But, I don't know if the target system would work correctly.


If I wanted /var on ZFS on a Debian system, I would "go the whole way" and STFW for a guide on building a Debian system with ZFS-on-root. Or, I would look for a Linux distribution (Ubuntu?) that can do ZFS-on-root OOTB. But, the best answer I have found for ZFS is FreeBSD.


David


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