14.2. Creating a Snapper Snapshot

Procedure 14.2. Creating a Post Snapshot

1. Determine the number of the pre snapshot:

   # snapper -c config_name list

   For example, to display the list of snapshots created using the configuration file lvm_config, use the following:

   # snapper -c lvm_config list
   Type   | # | Pre # | Date              | User | Cleanup  | Description | Userdata
   -------+---+-------+-------------------+------+----------+-------------+---------
   single | 0 |       |                   | root |          | current     |
   pre    | 1 |       | Mon 06<...>       | root |          |             |
   

   This output shows that the pre snapshot is number 1.
2. Create a post snapshot that is linked to a previously created pre snapshot:

   # snapper -c config_file create -t post --pre-num pre_snapshot_number

   • The -t post option specifies the creation of the post snapshot type.
   • The --pre-num option specifies the corresponding pre snapshot.
   For example, to create a post snapshot using the lvm_config configuration file and is linked to pre snapshot number 1, use:

   # snapper -c lvm_config create -t post --pre-num 1 -p
   2
   

   The -p option prints the number of the created snapshot and is optional.
3. The pre and post snapshots 1 and 2 are now created and paired. Verify this with the list command:

   # snapper -c lvm_config list
   Type   | # | Pre # | Date              | User | Cleanup  | Description | Userdata
   -------+---+-------+-------------------+------+----------+-------------+---------
   single | 0 |       |                   | root |          | current     |
   pre    | 1 |       | Mon 06<...>       | root |          |             |
   post   | 2 | 1     | Mon 06<...>       | root |          |             |
   

Procedure 14.3. Wrapping a Command in Pre and Post Snapshots

1. To wrap a command in pre and post snapshots:

   # snapper -c lvm_config create --command "command_to_be_tracked"

   For example, to track the creation of the /lvm_mount/hello_file file:

   # snapper -c lvm_config create --command "echo Hello > /lvm_mount/hello_file"

2. To verify this, use the status command:

   # snapper -c config_file status first_snapshot_number..second_snapshot_number

   For example, to track the changes made in the first step:

   # snapper -c lvm_config status 3..4
   +..... /lvm_mount/hello_file
   

   Use the list command to verify the number of the snapshot if needed.
   For more information on the status command, see Section 14.3, “Tracking Changes Between Snapper Snapshots”.