a snapper/btrfs exercise

// this is a comment
// if you need to replay this exercise you have to remove previous snapper configs:
// 1) edit /etc/sysconfig/snapper and remove appropriate entry
// 2) remove the file /etc/snapper/configs/test
//

// create a BTRFS on the spare disk
# mkfs.btrfs -f -L 'Test disk' /dev/sdh1
// lines removed for clarity
// ...
ID SIZE PATH
1 931.51GiB /dev/sdh1

// create a mount point and mount the btrfs on it
# mkdir /mnt/test
# mount /dev/sdh1 /mnt/test/

// verify there is no subvolumes yet
# btrfs subvolume list /mnt/test/
# // no output
// create a base folder to do our tests
# mkdir /mnt/test/myroot

// list the current snapper configurations
# snapper list-configs
Config | Subvolume
-------+----------
root | /
#

// create a snapper config
# snapper -c test create-config /mnt/test
# snapper list-configs
Config | Subvolume
-------+----------
root | /
test | /mnt/test
#

// verify that there is a .snapshots subvolume created by snapper
# btrfs subvolume list /mnt/test/
ID 256 gen 8 top level 5 path .snapshots
#

// and there is the current snapshot
# snapper -c test list
# | Type | Pre # | Date | User | Cleanup | Description | Userdata
---+--------+-------+------+------+---------+-------------+---------
0 | single | | | root | | current |
#

// create a initial snapshot the represent this currently empty FS
# snapper -c test create --description "Initial state"
# snapper -c test list
# | Type | Pre # | Date | User | Cleanup | Description | Userdata
---+--------+-------+--------------------------+------+---------+---------------+---------
0 | single | | | root | | current |
1 | single | | Sat Jul 9 14:31:56 2022 | root | | Initial state |


// lets modify the FS by creating some folders and dummy files
# mkdir /mnt/test/myroot/folder_{A,B,C,D}
# touch /mnt/test/myroot/folder_{A,B,C,D}/file_{1..9}
# tree /mnt/test/myroot
/mnt/test/myroot
├── folder_A
│** ├── file_1
│** ├── file_2
│** ├── file_3

// lines removed for clarity

└── folder_D

// lines removed for clarity

├── file_7
├── file_8
└── file_9

4 directories, 36 files
#

// lets create a snapshot before making changes
# snapper -c test create --description "before delete some files and folders"
# rm /mnt/test/myroot/folder_{A,B,C,D}/file_{1..5}
# tree /mnt/test/myroot/
/mnt/test/myroot/
├── folder_A
│** ├── file_6
│** ├── file_7
│** ├── file_8
│** └── file_9
├── folder_B
│** ├── file_6
│** ├── file_7
│** ├── file_8
│** └── file_9
├── folder_C
│** ├── file_6
│** ├── file_7
│** ├── file_8
│** └── file_9
└── folder_D
├── file_6
├── file_7
├── file_8
└── file_9

4 directories, 16 files
#

// lets make more changes but before, another snapshot
# snapper -c test create --description "before create files xxx"
# touch /mnt/test/myroot/folder_{A,B}/xxx_{1..5}
# tree /mnt/test/myroot
/mnt/test/myroot
├── folder_A
│** ├── file_6
│** ├── file_7

// lines removed for clarity

│** ├── xxx_1
│** ├── xxx_2
│** ├── xxx_3

// lines removed for clarity

├── file_8
└── file_9

4 directories, 26 files
#
// create a final snapshot
# snapper -c test create --description "done"

// lets check the list of snapshots and
// the list of the subvolumes created so far
# snapper -c test list
# | Type | Pre # | Date | User | Cleanup | Description | Userdata
---+--------+-------+--------------------------+------+----------+--------------------------------------+---------
0 | single | | | root | | current |
1 | single | | Sat Jul 9 17:58:08 2022 | root | | Initial state |
2 | single | | Sat Jul 9 17:59:53 2022 | root | | before delete some files and folders |
3 | single | | Sat Jul 9 18:00:00 2022 | root | timeline | timeline |
4 | single | | Sat Jul 9 18:00:10 2022 | root | | before create files xxx |
5 | single | | Sat Jul 9 18:00:31 2022 | root | | done |
# btrfs subvolume list /mnt/test/
ID 256 gen 17 top level 5 path .snapshots
ID 257 gen 10 top level 256 path .snapshots/1/snapshot
ID 258 gen 13 top level 256 path .snapshots/2/snapshot
ID 259 gen 14 top level 256 path .snapshots/3/snapshot
ID 260 gen 15 top level 256 path .snapshots/4/snapshot
ID 261 gen 16 top level 256 path .snapshots/5/snapshot
# btrfs subvolume get-default /mnt/test
ID 5 (FS_TREE)
#

// use snapper to check the difference between snapshots 5 (the current state) and 2 (just after creating the initial structure)
# snapper -c test list
# | Type | Pre # | Date | User | Cleanup | Description | Userdata
---+--------+-------+--------------------------+------+----------+--------------------------------------+---------
0 | single | | | root | | current |
1 | single | | Sat Jul 9 17:58:08 2022 | root | | Initial state |
2 | single | | Sat Jul 9 17:59:53 2022 | root | | before delete some files and folders |
3 | single | | Sat Jul 9 18:00:00 2022 | root | timeline | timeline |
4 | single | | Sat Jul 9 18:00:10 2022 | root | | before create files xxx |
5 | single | | Sat Jul 9 18:00:31 2022 | root | | done |
kimera:~ # snapper -c test status 5..2
+..... /mnt/test/myroot/folder_A/file_1
+..... /mnt/test/myroot/folder_A/file_2
+..... /mnt/test/myroot/folder_A/file_3
// lines removed for clarity
-..... /mnt/test/myroot/folder_B/xxx_3
-..... /mnt/test/myroot/folder_B/xxx_4
-..... /mnt/test/myroot/folder_B/xxx_5
+..... /mnt/test/myroot/folder_C/file_1
+..... /mnt/test/myroot/folder_C/file_2
// lines removed for clarity
+..... /mnt/test/myroot/folder_D/file_5
#

// use snapper to roolback to snapshot 2
# # snapper -c test undochange 2..5
create:20 modify:0 delete:10
kimera:~ # tree /mnt/test/myroot/
/mnt/test/myroot/
├── folder_A
│ ├── file_1
│ ├── file_2
│ ├── file_3
// lines removed for clarity
├── file_7
├── file_8
└── file_9

4 directories, 36 files
// done