Renaming and replacing zroot filesystems using mfsBSD

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This might have interesting tidbits. It’s a draft from June 2020 where I was renaming filesystems when booting from a live thumbdrive.

I am replacing one zroot with another because of missing binaries and suspect layout. The existing zroot is an old system predating current zroot layouts.

I have already copied over some filesystems via zfs send | zfs recv over ssh.

I will now try renaming the filesystems on the new drives and retain a able system.

This work is being performed on a test system (that link is not safe for young eyes).

In this post:

  • FreeBSD 12.1
  • mfsBSD 12.1

About this thumb drive

I wrote about burning a thumb drive image to a USB drive.

I’ve booted the test system from that thumbdrive.

Next, I will manipulate those new drives.

Logging into mfsBSD

One of the lovely features of mfsBSD is it allows me to ssh as root for this task. This is not something one should normally do, but this is not a normal circumstance.

$ ssh root@10.0.0.247
The authenticity of host '10.0.0.247 (10.55.0.247)' can't be established.
ECDSA key fingerprint is SHA256:8ysqgLdw3eU29srXdNlyze6QqF5ztkKq4HwaucLO/Z8.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '10.0.0.247' (ECDSA) to the list of known hosts.
Password for root@mfsbsd:

The password is: mfsroot.

Before we get started

I started down a rabbit-hole, got confused, and started again another day.

I kept what I wrote, because it might contains stuff which might help you.

The rabbit hole starts here

Looking around

Let’s see what we have:

root@mfsbsd:~ # zfs list
no datasets available

This is also good. Nothing to conflict with.

Import without mounting

I want to import zroot without mounting any of the filesystems. If I were to mount it, things would get overlaid on top of the existing mfsBSD filesystem. I don’t want that. I just want to rename stuff, set properties, perhaps delete some stuff.

From man zpool, I want -N:

root@mfsbsd:~ # zpool import -N zroot
root@mfsbsd:~ # zfs list
NAME                  USED  AVAIL  REFER  MOUNTPOINT
zroot                8.63G   197G    88K  /zroot
zroot/ROOT            757M   197G    88K  none
zroot/ROOT/default    479M   197G   477M  /
zroot/ROOT/default1   278M   197G   275M  /zroot/default1
zroot/tmp            1.26M   197G    88K  /tmp
zroot/usr             625M   197G    88K  /usr
zroot/usr/home        188K   197G   124K  /usr/home
zroot/usr/local       625M   197G   625M  /usr/local
zroot/usr1           1.26G   197G  1.26G  /zroot/usr1
zroot/var            3.73M   197G    88K  /var
zroot/var/audit        88K   197G    88K  /var/audit
zroot/var/crash        88K   197G    88K  /var/crash
zroot/var/log         776K   197G   172K  /var/log
zroot/var/log1       2.48M   197G  2.48M  /var/log1
zroot/var/mail        144K   197G    88K  /var/mail
zroot/var/tmp         104K   197G    88K  /var/tmp
zroot/var1           6.01G   197G  6.01G  /zroot/var1
root@mfsbsd:~ #

Yes, that looks right.

rename, move, etc

Let’s rename some stuff, moving the original stuff out of the way and moving in the old stuff.

root@mfsbsd:~ # zfs create zroot/original
root@mfsbsd:~ # zfs rename zroot/ROOT/default zroot/original/default
root@mfsbsd:~ # zfs rename zroot/usr          zroot/original/usr
root@mfsbsd:~ # zfs rename zroot/var/log      zroot/original/log
root@mfsbsd:~ # zfs rename zroot/var          zroot/original/var

Let’s see:

NAME                       USED  AVAIL  REFER  MOUNTPOINT
zroot                     8.63G   197G    88K  /zroot
zroot/ROOT                 278M   197G    88K  none
zroot/ROOT/default1        278M   197G   275M  /zroot/default1
zroot/original            1.08G   197G    88K  /zroot/original
zroot/original/default     479M   197G   477M  /
zroot/original/log         776K   197G   172K  /zroot/original/log
zroot/original/usr         625M   197G    88K  /usr
zroot/original/usr/home    188K   197G   124K  /usr/home
zroot/original/usr/local   625M   197G   625M  /usr/local
zroot/original/var        2.98M   197G    88K  /var
zroot/original/var/audit    88K   197G    88K  /var/audit
zroot/original/var/crash    88K   197G    88K  /var/crash
zroot/original/var/log1   2.48M   197G  2.48M  /var/log1
zroot/original/var/mail    144K   197G    88K  /var/mail
zroot/original/var/tmp     104K   197G    88K  /var/tmp
zroot/tmp                 1.26M   197G    88K  /tmp
zroot/usr1                1.26G   197G  1.26G  /zroot/usr1
zroot/var1                6.01G   197G  6.01G  /zroot/var1
root@mfsbsd:~ #

Let’s fix up that var anomaly shall we?

root@mfsbsd:~ # zfs rename zroot/var1 zroot/var
root@mfsbsd:~ # zfs rename zroot/original/var/audit zroot/var/audit
root@mfsbsd:~ # zfs rename zroot/original/var/crash zroot/var/crash
root@mfsbsd:~ # zfs rename zroot/original/var/log1  zroot/var/log
root@mfsbsd:~ # zfs rename zroot/original/var/mail  zroot/var/mail
root@mfsbsd:~ # zfs rename zroot/original/var/tmp   zroot/var/tmp
root@mfsbsd:~ # zfs list
NAME                       USED  AVAIL  REFER  MOUNTPOINT
zroot                     8.63G   197G    88K  /zroot
zroot/ROOT                 278M   197G    88K  none
zroot/ROOT/default1        278M   197G   275M  /zroot/default1
zroot/original            1.08G   197G    88K  /zroot/original
zroot/original/default     479M   197G   477M  /
zroot/original/log         776K   197G   172K  /zroot/original/log
zroot/original/usr         625M   197G    88K  /usr
zroot/original/usr/home    188K   197G   124K  /usr/home
zroot/original/usr/local   625M   197G   625M  /usr/local
zroot/original/var          88K   197G    88K  /var
zroot/tmp                 1.26M   197G    88K  /tmp
zroot/usr1                1.26G   197G  1.26G  /zroot/usr1
zroot/var                 6.01G   197G  6.01G  /zroot/var
zroot/var/audit             88K   197G    88K  /zroot/var/audit
zroot/var/crash             88K   197G    88K  /zroot/var/crash
zroot/var/log             2.48M   197G  2.48M  /zroot/var/log
zroot/var/mail             144K   197G    88K  /zroot/var/mail
zroot/var/tmp              104K   197G    88K  /zroot/var/tmp
root@mfsbsd:~ #

Next up, usr:

root@mfsbsd:~ # zfs rename zroot/usr1 zroot/usr
root@mfsbsd:~ # zfs rename zroot/original/usr/home zroot/usr/home
root@mfsbsd:~ # zfs list
NAME                       USED  AVAIL  REFER  MOUNTPOINT
zroot                     8.63G   197G    88K  /zroot
zroot/ROOT                 278M   197G    88K  none
zroot/ROOT/default1        278M   197G   275M  /zroot/default1
zroot/original            1.08G   197G    88K  /zroot/original
zroot/original/default     479M   197G   477M  /
zroot/original/log         776K   197G   172K  /zroot/original/log
zroot/original/usr         625M   197G    88K  /usr
zroot/original/usr/local   625M   197G   625M  /usr/local
zroot/original/var          88K   197G    88K  /var
zroot/tmp                 1.26M   197G    88K  /tmp
zroot/usr                 1.26G   197G  1.26G  /zroot/usr
zroot/usr/home             188K   197G   124K  /zroot/usr/home
zroot/var                 6.01G   197G  6.01G  /zroot/var
zroot/var/audit             88K   197G    88K  /zroot/var/audit
zroot/var/crash             88K   197G    88K  /zroot/var/crash
zroot/var/log             2.48M   197G  2.48M  /zroot/var/log
zroot/var/mail             144K   197G    88K  /zroot/var/mail
zroot/var/tmp              104K   197G    88K  /zroot/var/tmp
root@mfsbsd:~ #

Then much more happened…

Nope, not going to show my work

This is getting complex in my head and I’m having trouble keeping it straight *and* documenting it at the same time.

Instead, I will work on it and show my work later.

The rabbit hole ends here

This is what I have now

After sitting down and quietly thinking about where things were, I have this:

root@mfsbsd:~ # zpool import -o altroot=/import zroot
root@mfsbsd:~ # zfs list
NAME                     USED  AVAIL  REFER  MOUNTPOINT
zroot                   8.63G   197G    96K  /import/zroot
zroot/ROOT               278M   197G    88K  none
zroot/ROOT/default       278M   197G   275M  /import
zroot/original           481M   197G    88K  none
zroot/original/default   480M   197G   477M  none
zroot/original/log       776K   197G   172K  none
zroot/original/usr        88K   197G    88K  none
zroot/original/var        88K   197G    88K  none
zroot/tmp               1.11M   197G    88K  /import/tmp
zroot/usr               1.87G   197G  1.26G  /import/usr
zroot/usr/home           188K   197G   124K  /import/usr/home
zroot/usr/local          625M   197G   625M  /import/usr/local
zroot/var               6.01G   197G  6.01G  /import/var
zroot/var/audit           88K   197G    88K  /import/var/audit
zroot/var/crash           88K   197G    88K  /import/var/crash
zroot/var/log           2.63M   197G  2.52M  /import/var/log
zroot/var/mail           144K   197G    88K  /import/var/mail
zroot/var/tmp            112K   197G    88K  /import/var/tmp
root@mfsbsd:~ #

I have compared various things between the old drives and the new drives. This includes directory listings for:

  • /
  • /etc
  • /usr
  • /usr/local
  • /usr/local/etc
  • /usr/local/etc/rc.d

I also visually compared /etc/rc.conf on both sets of drives.

I want to try booting from the new drives first. I can’t do that until later today.

Things left to do

I need to do another round of zfs send | zfs recv before this goes live.

Add a different IP address so this doesn’t boot and conflict with the production server. I thought I might be able to use /etc/rc.conf.local to override settings within /etc/rc.conf. Then I realized there were 36 ifconfig_ix2_alias entries to change… I didn’t bother.

Instead, I saved the original rc.conf away, and created a temporary one.


# cat /import/etc/rc.conf
defaultrouter=”10.0.0.1″
ifconfig_ix2=”inet 10.0.0.56 netmask 255.255.255.0″

hostname=”newslocum.int.unixathome.org”

#gateway_enable=”YES”

ntpd_enable=”YES”
ntpd_flags=”-L”
daily_ntpd_leapfile_enable=”YES”
daily_ntpd_avoid_congestion=”YES”

keymap=”us”
sshd_enable=”YES”
zfs_enable=YES

First boot attempt

The first boot failed. Nothing in /dev. Here’s a couple of screen shots I took. This is an aging but useful monitor. Please forgive the haziness of the top few lines.

I rebooted into mfsBSD, imported the zpool (with an altroot) and found:

root@mfsbsd:~ # zpool import -o altroot=/import zroot
root@mfsbsd:~ # cd /import/dev
root@mfsbsd:/import/dev # ls -l
total 1
lrwxr-xr-x  1 root  wheel  12 Jun 14 16:36 log -> /var/run/log
-rw-r--r--  1 root  wheel   0 Jun 15 21:08 null

Oh. Damn.

And that’s where I stopped.

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