Juniper SRX – error: Could not format alternate root | Solution

srx-01This week I encountered this error for the first time in the years I’m working with JunOS now. Last week I installed two SRX’s at a remote datacenter location in NJ, US. All working fine and once back in my home country I added some monitoring checks to the devices and thought, well lets sync the JunOS alternate partition with the primary. This went just fine:

onno@net> show system snapshot media internal
Information for snapshot on       internal (/dev/da0s1a) (backup)
Creation date: Aug 29 13:54:23 2015
JUNOS version on snapshot:
junos  : 12.1X44-D35.5-domestic
Information for snapshot on       internal (/dev/da0s2a) (primary)
Creation date: Apr 7 13:29:14 2016
JUNOS version on snapshot:
junos  : 12.1X46-D40.2-domestic

onno@net> request system snapshot slice alternate
Formatting alternate root (/dev/da0s1a)…
Copying ‘/dev/da0s2a’ to ‘/dev/da0s1a’ .. (this may take a few minutes)
The following filesystems were archived: /

Then I wanted to double check it both partitions contained the same version, and then I got the error:

onno@net> show system snapshot media internal
error: cannot mount /dev/da0s1a

Eehhh .. wait .. what? That’s not something you want to see on a SRX more than 6000km away. (this is a location with, for now, single internet connection)
So I retried the request snapshot command, without success:

onno@net> request system snapshot slice alternate
Formatting alternate root (/dev/da0s1a)…
error: Could not format alternate root

After digging around I found similar issues on EX’s which were cause by the backup partition still mounted. However I didn’t find the /dev/da0s1a mounted, but did find the following:

onno@net> start shell
% mount
(snip)
/dev/altroot on /altroot (ufs, local, noatime, soft-updates)
(snip)

Solution

Looking at the other SRX, there was no /dev/altroot mounted. So I just unmounted it, and ran the same commands again. Now there’s no error and all fine:

onno@net> start shell
% su –
Password:
root@net% umount /altroot
root@net% exit
logout
% exit
exit
onno@net> request system snapshot slice alternate
Formatting alternate root (/dev/da0s1a)…
Copying ‘/dev/da0s2a’ to ‘/dev/da0s1a’ .. (this may take a few minutes)
The following filesystems were archived: /

onno@net> show system snapshot media internal
Information for snapshot on       internal (/dev/da0s1a) (backup)
Creation date: Apr 15 07:30:11 2016
JUNOS version on snapshot:
junos  : 12.1X46-D40.2-domestic
Information for snapshot on       internal (/dev/da0s2a) (primary)
Creation date: Apr 7 13:29:14 2016
JUNOS version on snapshot:
junos  : 12.1X46-D40.2-domestic

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9 Responses to Juniper SRX – error: Could not format alternate root | Solution

  1. Edin says:

    Thanks Onno,

    your post solved same issue on SRX650. Many thanks.

  2. Estre says:

    Great post. Very helpfull. You saved me. Thanks a lot

  3. Mechanix says:

    Great, thank you!!!

  4. John Simon says:

    Great it helped!

  5. Simon Brooks says:

    Helped very much on a SRX 650! Thank you

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