Description

This article explains the difference between 'request vmhost snapshot recovery' and 'request system snapshot recovery' and how they work.

Solution

For NG-RE:

NG-RE has two disk's in it: disk1 and disk2. Disk1 is Primary and disk 2 is backup.
Boot disk = Primary == disk1
Boot disk = Secondary == disk2
The RE by default boots up in disk1.

request vmhost snapshot   

Take a snapshot of the currently running and active file system partitions from the primary disk to the secondary disk to recover the secondary disk in case of failure. 
(i.e copies all the file's from primary disk to secondary disk,)   deletes all the content of the secondary disk.
Works only when RE is booted by in primary disk (disk1).

 

request vmhost snapshot recovery 

Take a snapshot of the currently running and active file system partitions from the secondary disk to the primary disk. 
(i.e copies all the file's from secondary disk to primary disk,) deletes all the content of the primary disk.
Works only when RE is booted by in secondary disk (disk2)

 

Example:

The snapshot is taken when RE is booted from the default disk (Primary disk):

labroot@mx2020-re0> request vmhost snapshot             
warning: Existing data on the target may be lost
Proceed ? [yes,no] (no) yes 

warning: Proceeding with vmhost snapshot
Current root details,           Device sda, Label: jrootp_P, Partition: sda3
Snapshot admin context from current boot disk to target disk ...
Proceeding with snapshot on secondary disk
Mounting device in preparation for snapshot...
Cleaning up target disk for snapshot ...
Creating snapshot on target disk from current boot disk ...
Snapshot created on secondary disk.
Software snapshot done

 

The 'request vmhost snapshot recovery' CLI  fails to work as the RE is booted by in primary disk:

labroot@mx2020-re0> request vmhost snapshot recovery 
warning: Existing data on the target may be lost
Proceed ? [yes,no] (no) yes 

warning: Proceeding with vmhost snapshot
Current root details,           Device sda, Label: jrootp_P, Partition: sda3
Already running from primary disk.
Please try snapshot without recovery option!
Snapshot aborted.

 

The below command displays that the snapshot is done to which disk and the time of snapshot:

"Secondary Disk" == disk2
"Snapshot Time: Fri May 14 19:37:55 UTC 2021" = Time of snapshot

labroot@mx2020-re0> show vmhost snapshot 
UEFI    Version: NGRE_v00.53.00.01

Secondary Disk, Snapshot Time: Fri May 14 19:37:55 UTC 2021

Version: set p
VMHost Version: 3.1198
VMHost Root: vmhost-x86_64-16.1R6-20171026_0422_builder
VMHost Core: vmhost-core-x86_64-16.1R6-20171026_0422_builder
kernel: 3.10.79-ovp-rt74-WR6.0.0.20_preempt-rt
Junos Disk: junos-install-x86-64-16.1R6-S3.1

Version: set b
VMHost Version: 3.1465
VMHost Root: vmhost-x86_64-17.3R3-S8-20200319_0024_builder
VMHost Core: vmhost-core-x86_64-17.3R3-S11-20210118_2225_builder
kernel: 3.10.100-ovp-rt110-WR6.0.0.31_preempt-rt
Junos Disk: junos-install-mx-x86-64-17.3R3-S11.4
 

For non NG-RE

request system snapshot recovery

Create a recovery snapshot and store it in the  /oam  volume.
A recovery snapshot stored in OAM (Operations, Administration, and Maintenance) volume holds a full backup that can be used in case something goes wrong with Junos volume. (i.e stored in the flash disk)

 

request system snapshot 

A non-recovery snapshot is stored in Junos OS volume used for running the device software and hold the configuration and the logs.

Example:

labroot@mx240-re0> request system snapshot 
NOTICE: Snapshot snap.20210514.195000 created successfully

labroot@jtac-mx240-r2008-re0> request system snapshot recovery 
Creating image ...
Compressing image ...
Image size is 2998MB
ln: ../manifest: No such file or directory
ln: ../manifest.e*: No such file or directory
Recovery snapshot created successfully

Modification History

21-12-24: Added links to description of "request vmhost snapshot" and "request system snapshot" commands.

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