Issue #2187 - disklayout.conf file contains duplicate lines

[rmetrich]

#1356 ## Relax-and-Recover (ReaR) Pull Request Template

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Pull Request Details:

• Type: Bug Fix

• Impact: Low

• Reference to related issue (URL): disklayout.conf file contains duplicate lines #2187

• How was this pull request tested? Tested on RHEL8 with multiple segments

• Brief description of the changes in this pull request:

Create the 'lvmvol' lines commented out when multiple segments exist for a given LV.
This is not an issue unless Migration Mode is used.
In such case, using 'lvcreate' commands already does best effort and loses LV information.

Reproducer:

1. Add 2 disks to an existing system

2. Create a VG with the disks

   # vgcreate data /dev/sdb /dev/sdc
   

3. Create 2 LVs with segments

   # lvcreate -n lv1 -L 1G data
   # lvcreate -n lv2 -L 1G data
   # lvextend /dev/data/lv1 -L +1G -i 2
   # lvextend /dev/data/lv2 -L +1G -i 2
   # lvextend /dev/data/lv1 -L +1G -i 1
   # lvextend /dev/data/lv2 -L +1G -i 1
   

4. Format and mount the LVs

   # mkdir -p /lv1 /lv2
   # mkfs.ext4 /dev/data/lv1
   # mkfs.ext4 /dev/data/lv2
   # mount /dev/data/lv1 /lv1
   # mount /dev/data/lv2 /lv2
   

5. Create rescue ISO

6. Check /var/lib/rear/layout/disklayout.conf

   # Format for LVM LVs
   # lvmvol <volume_group> <name> <size(bytes)> <layout> [key:value ...]
   # WARNING: Volume data/lv1 has multiple segments. Restoring it in Migration Mode using 'lvcreate' won't preserve segments and volume properties of the other segments!
   lvmvol /dev/data lv1 3221225472b linear,striped segmentsize:1073741824b stripes:1
   #lvmvol /dev/data lv1 3221225472b linear,striped stripesize:65536b segmentsize:1073741824b stripes:2
   #lvmvol /dev/data lv1 3221225472b linear,striped segmentsize:1073741824b stripes:1
   # WARNING: Volume data/lv2 has multiple segments. Restoring it in Migration Mode using 'lvcreate' won't preserve segments and volume properties of the other segments!
   lvmvol /dev/data lv2 2147483648b linear,striped segmentsize:1073741824b stripes:1
   #lvmvol /dev/data lv2 2147483648b linear,striped stripesize:65536b segmentsize:1073741824b stripes:2
   

With the fix (see above), the other segments of the LV lv1 and lv2 are created commented out, which allows the administrator to recreate them manually if needed.
Note in particular that lvcreate code will create the lv1 and lv2 LVs with only 1 stripe, i.e. the number of stripes specified for the first segment only.

[gdha]

@rmetrich Looks good on first sight - will you also back-port this in RedHat's rear-2.4 package?

[pcahyna]

@rmetrich to me it seems like an abuse of the kval variable to put segmentsize into it, since unlike the others it is not a valid option for lvcreate. I thus submitted #2196 to change this, if you agree.

[rmetrich]

Huh, what? Abuse?
OK, I recognize I was lazy here :-) Thanks for the PR.