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[EX] "show system snapshot media internal all-members" output throws "cannot mount /dev/da0sxa" error

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Article ID: KB28238 KB Last Updated: 04 Jun 2020Version: 4.0
Summary:

When the command show system snapshot media internal command is executed, sometimes the output is not populated correctly, and the following error is reported:

pcx:error: cannot mount /dev/da0sxa

This article explains why the error is observed and details the steps to recover the system from this state.

 

Symptoms:

The show system snapshot media internal command is used to display the software version that is available on the two slices/partitions as well as to indicate which of the two partitions is the active partition.

In some instances, the output of this command does not display the complete information, and displays an error stating that the alternate partition cannot be mounted. For example, the following output collected on a three-member VC indicates that an error was encountered while collecting the snapshot information on the backup partition (/dev/da0s1a).

root> show system snapshot media internal | no-more
fpc0:
--------------------------------------------------------------------------
Information for snapshot on internal (/dev/da0s1a) (backup)
Creation date: Aug 24 11:26:29 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1
Information for snapshot on internal (/dev/da0s2a) (primary)
Creation date: Aug 24 10:52:41 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1

fpc1:
--------------------------------------------------------------------------
error: cannot mount /dev/da0s1a

fpc2:
--------------------------------------------------------------------------
Information for snapshot on internal (/dev/da0s1a) (backup)
Creation date: Nov 4 11:56:59 2011
JUNOS version on snapshot:
jbase : 11.1R6.4
jcrypto-ex: 11.1R6.4
jdocs-ex: 11.1R6.4
jkernel-ex: 11.1R6.4
jroute-ex: 11.1R6.4
jswitch-ex: 11.1R6.4
jweb-ex: 11.1R6.4
jpfe-ex42x: 11.1R6.4
Information for snapshot on internal (/dev/da0s2a) (primary)
Creation date: Aug 24 10:52:40 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1

 

Cause:

When the show system snapshot media internal command is issued, the system has to mount the alternate partition at a temporary mount point /tmp/snap-tmp.xxxx/mnt.xxxx in order to verify the software packages that are installed on that partition. The alternate partition is unmounted once the command is successfully executed. If, for some reason, this command is aborted while the output is being displayed, the alternate partition will remain mounted.

This can happen if any of the following activities take place when the command is running:

  • Entering "q" to quit

  • Entering "control + c"

  • Terminating the ssh / telnet session

Any subsequent snapshot-related commands will then error out since the system will not be able to mount the alternate partition.

 

Solution:

To resolve this issue, the alternate partition that is mounted at the temporary mount point must be manually unmounted. The following example explains the procedure to identify and unmount the alternate partition.

Note: You must log in as root to execute this procedure.

  1. We have a three-member VC where we run the show system snapshot media alternate command. The command displays the following error for member 1:

root> show system snapshot media internal | no-more
fpc0:
--------------------------------------------------------------------------
Information for snapshot on internal (/dev/da0s1a) (backup)
Creation date: Aug 24 11:26:29 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1
Information for snapshot on internal (/dev/da0s2a) (primary)
Creation date: Aug 24 10:52:41 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1

fpc1:
------------------------------------------------------------
error: cannot mount /dev/da0s1a

fpc2:
------------------------------------------------------------
Information for snapshot on internal (/dev/da0s1a) (backup)
Creation date: Nov 4 11:56:59 2011
JUNOS version on snapshot:
jbase : 11.1R6.4
jcrypto-ex: 11.1R6.4
jdocs-ex: 11.1R6.4
jkernel-ex: 11.1R6.4
jroute-ex: 11.1R6.4
jswitch-ex: 11.1R6.4
jweb-ex: 11.1R6.4
jpfe-ex42x: 11.1R6.4
Information for snapshot on internal (/dev/da0s2a) (primary)
Creation date: Aug 24 10:52:40 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1
  1. To check the temporary mount point for the alternate partition, we can use the shell command df -h. If the error is seen for a member of the VC that is not the master, we will have to first log in to the member before running the following command:

{master:0}
root> request session member 1

--- JUNOS 12.1R3-S1 built 2012-08-24 07:51:52 UTC

root@:LC:1% df -h
Filesystem Size Used Avail Capacity Mounted on
/dev/da0s2a 183M 114M 54M 68% /  <--- this is the active partition
devfs 1.0K 1.0K 0B 100% /dev
/dev/md0 40M 40M 0B 100% /packages/mnt/jbase
/dev/md1 1.5M 1.5M 0B 100% /packages/mnt/fips-mode-powerpc-12.1R3-S1
/dev/md2 9.0M 4.4M 3.9M 53% /packages/mfs-jcrypto-ex
/dev/md3 13M 13M 0B 100% /packages/mnt/jcrypto-ex-12.1R3-S1
/dev/md4 9.0M 4.4M 3.9M 53% /packages/mfs-jdocs-ex
/dev/md5 7.6M 7.6M 0B 100% /packages/mnt/jdocs-ex-12.1R3-S1
/dev/md6 41M 37M 836K 98% /packages/mfs-jkernel-ex
/dev/md7 91M 91M 0B 100% /packages/mnt/jkernel-ex-12.1R3-S1
/dev/md8 12M 7.1M 3.6M 66% /packages/mfs-jpfe-ex42x
/dev/md9 20M 20M 0B 100% /packages/mnt/jpfe-ex42x-12.1R3-S1
/dev/md10 16M 11M 3.2M 78% /packages/mfs-jroute-ex
/dev/md11 36M 36M 0B 100% /packages/mnt/jroute-ex-12.1R3-S1
/dev/md12 11M 6.5M 3.7M 64% /packages/mfs-jswitch-ex
/dev/md13 19M 19M 0B 100% /packages/mnt/jswitch-ex-12.1R3-S1
/dev/md14 12M 7.6M 3.6M 68% /packages/mfs-jweb-ex
/dev/md15 20M 20M 0B 100% /packages/mnt/jweb-ex-12.1R3-S1
/dev/md16 126M 64K 116M 0% /tmp
/dev/da0s3e 123M 746K 112M 1% /var
/dev/da0s3d 369M 130K 339M 0% /var/tmp
/dev/da0s4d 62M 78K 57M 0% /config
/dev/md17 118M 17M 91M 16% /var/rundb
procfs 4.0K 4.0K 0B 100% /proc
/var/jail/etc 123M 746K 112M 1% /packages/mnt/jweb-ex-12.1R3-S1/jail/var/etc
/var/jail/run 123M 746K 112M 1% /packages/mnt/jweb-ex-12.1R3-S1/jail/var/run
/var/jail/tmp 123M 746K 112M 1% /packages/mnt/jweb-ex-12.1R3-S1/jail/var/tmp
/var/tmp 369M 130K 339M 0% /packages/mnt/jweb-ex-12.1R3-S1/jail/var/tmp/uploads
devfs 1.0K 1.0K 0B 100% /packages/mnt/jweb-ex-12.1R3-S1/jail/dev
/dev/da0s1a 184M 114M 55M 67% /tmp/snap-tmp.5361/mnt.5361   <---  this is the alternate partition      
root@:LC:1%
  1. The output displayed above shows that the alternate partition is mounted at the temp mount point: /tmp/snap-tmp.5361/mnt.5361.

  2. Once we know the mount point, the alternate partition can be unmounted by using the shell command umount:

root@:LC:1% umount /tmp/snap-tmp.5361/mnt.5361
  1. Once the partition is unmounted, we can run the command again to check that the output is populated correctly, which it is in the following output:

root> show system snapshot media internal
fpc0:
--------------------------------------------------------------------------
Information for snapshot on internal (/dev/da0s1a) (backup)
Creation date: Aug 24 11:26:29 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1
Information for snapshot on internal (/dev/da0s2a) (primary)
Creation date: Aug 24 10:52:41 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1

fpc1:
--------------------------------------------------------------------------
Information for snapshot on internal (/dev/da0s1a) (backup)
Creation date: Aug 24 11:30:34 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1
Information for snapshot on internal (/dev/da0s2a) (primary)
Creation date: Aug 24 10:52:41 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1

fpc2:
--------------------------------------------------------------------------
Information for snapshot on internal (/dev/da0s1a) (backup)
Creation date: Nov 4 11:56:59 2011
JUNOS version on snapshot:
jbase : 11.1R6.4
jcrypto-ex: 11.1R6.4
jdocs-ex: 11.1R6.4
jkernel-ex: 11.1R6.4
jroute-ex: 11.1R6.4
jswitch-ex: 11.1R6.4
jweb-ex: 11.1R6.4
jpfe-ex42x: 11.1R6.4
Information for snapshot on internal (/dev/da0s2a) (primary)
Creation date: Aug 24 10:52:40 2012
JUNOS version on snapshot:
jbase : ex-12.1R3-S1
jcrypto-ex: 12.1R3-S1
jdocs-ex: 12.1R3-S1
jkernel-ex: 12.1R3-S1
jroute-ex: 12.1R3-S1
jswitch-ex: 12.1R3-S1
jweb-ex: 12.1R3-S1
jpfe-ex42x: 12.1R3-S1

If you are not able to see the temporary mount point for the alternate partition by using df -h, then a chassis reboot will help to unmount the alternate partition. It is recommended, however, to reboot the chassis during a maintenance window.

Note: If it is a VC, then the reboot is required only for that specific member.

 

Modification History:
  • 2020-06-04: Added a line to reboot the chassis to unmount the partition if you are not able to see the temporary mount point for the alternate partition by using df -h

  • 2020-03-04: Article reviewed for accuracy. No changes made. Article is correct and complete.

  • 2017-10-19: Changed 'show system' command ‚Äčto 'show system snapshot' command.

 

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