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[EX] Recovering from the "not a JUNOS snapshot" error

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Article ID: KB32880 KB Last Updated: 03 Apr 2019Version: 1.0
Summary:

When there are bad blocks, users may encounter the /dev/da0s1a is not a JUNOS snapshot error on EX Series switches.

This article explains how to recover the switch or virtual chassis from the error.

 

Symptoms:

The output of show system snapshot media internal says /dev/da0s1a is not a JUNOS snapshot.

labroot@jtac> show system snapshot media internal
fpc0:
--------------------------------------------------------------------------
error: /dev/da0s1a is not a JUNOS snapshot

fpc1:
--------------------------------------------------------------------------
error: /dev/da0s1a is not a JUNOS snapshot

 

Cause:

This might be because the /var/tmp directory is full or at more than 82% storage due to which the image cannot be uncompressed or because there has been an ungraceful shutdown, which has led to corruption of partitions or flash corruption.

 

Solution:

To check for any file system corruption, perform the following:

  1. Log in as root user to the shell.
> start shell user root
  1. Check if any bad blocks exist currently on the master.

% nand-mediack –C  

If there are any bad blocks, a sequence of output will be generated.

  1. To clear the bad blocks, execute the following:
% nand-mediack     
% fsck –f
  1. Check again if any bad blocks exist.

% nand-mediack –C

For more information, see KB20570 - [EX/SRX] Recovering from file system corruption during a system reboot, NAND media utility checks for bad blocks in the NAND flash memory.

Note: After step 4, if the bad blocks still exist, perform the previous steps a few more times to clear the bad blocks. If they continue to exist, it could be a faulty hardware and there may be a need to replace it. Contact Support in this case.

 

If there are no more bad blocks, continue to the following steps:

  1. Copy the required image to the master and perform the following steps to write a proper Junos OS snapshot.
request system software add <filepath> member <memberid> reboot
  1. After the master comes up, execute the show version command, verify the output, and then proceed to create a snapshot as follows:

request system snapshot slice alternate

labroot@jtac > show system snapshot media internal
fpc0:
--------------------------------------------------------------------------
Information for snapshot on       internal (/dev/da0s1a) (primary)
Creation date: Jan 14 00:33:17 2019
JUNOS version on snapshot:
  jdocs-ex: 14.1X53-D40.8
  junos  : ex-14.1X53-D40.8
  junos-ex-4300: 14.1X53-D40.8
  jweb-ex: 14.1X53-D40.8
Information for snapshot on       internal (/dev/da0s2a) (backup)
Creation date: Jan 13 19:32:09 2019
JUNOS version on snapshot:
  jdocs-ex: 14.1X53-D47.6
  junos  : ex-14.1X53-D47.6
  junos-ex-4300: 14.1X53-D47.6
  jweb-ex: 14.1X53-D47.6
  1. In case there is an issue with the master booting up, we will have to perform a format installation through a USB.

    1. We need to first format the USB with the FAT32 file system. Copy only the Junos OS release 12.3 image to the USB. Interrupt the boot-sequence by using the spacebar to get into loader prompt: loader>
    2. Execute the following command:  

      install file:///jinstall-ex-version-domestic-signed.tgz
      

    3. Execute the show version command to verify the installation:

labroot@jtac> show version
fpc0:
--------------------------------------------------------------------------
Hostname: jtac-EX4300-24T-r010
Model: ex4300-24t
Junos: 14.1X53-D40.8
JUNOS EX  Software Suite [14.1X53-D40.8]
JUNOS FIPS mode utilities [14.1X53-D40.8]
JUNOS Online Documentation [14.1X53-D40.8]
JUNOS EX 4300 Software Suite [14.1X53-D40.8]
JUNOS Web Management Platform Package [14.1X53-D40.8]
JUNOS py-base-powerpc [14.1X53-D40.8]

For more information, see KB20643 - [EX Switch] Rewrite the entire file system by issuing "install --format" command from "Loader" mode (Format Install).

 

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