[CentOS] offline root lvm resize

[Sean Hart]

On Sat, Jul 30, 2011 at 7:40 AM, Alexander Dalloz <ad+lists at uni-x.org> wrote:
> Am 30.07.2011 10:37, schrieb Sean Hart:
>> So here goes...
>> First some back story
>>      -Centos 5 with latest updates as of yesterday. kernel is
>> 2.6.18-238.19.1.el5
>>      -setup is raid 1 for /boot and lvm over raid6 for everything else
>>
>>      -  The / partition (lvm "RootVol") had run out of room... (100%
>> full, things where falling appart...)
>>
>> I resized the root volume (from 20GiB to 50GiB). This was done from a
>> fedora 15 livecd, seemed like a better idea than doing it on a live
>> system at the time.... After the resize the content of all the lvs
>> could be mounted and all data was still there (all this from within
>> fedora).
>
> You would better have used the CentOS 5 install media to run into rescue
> mode and then to chroot into the system, given you felt better to do an
> offline resizing. Though online resizing (increasing an LV) is trouble
> free from my experience. Well, if / is completely full the offline route
> may indeed be better.
>
>> The problem is when i try to reboot into centos as the root volume
>> cannot be found.
>>
>> boot message goes as follows
>>
>> ...
>> No Volume groups found
>> Volume Group "RaidVolGrp" not found
>> ...
>> Kernel panic
>>
>>
>> the UUID's have not changed, but there is definitely a missing link,
>> probably something dumb...
>>
>> I would greatly appreciate if anyone could help point me in the right
>> direction..
>>
>> a bit more info
>>
>> # lvscan
>>   ACTIVE            '/dev/RaidVolGrp/RootVol' [50.00 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/HomeVol' [250.00 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/SwapVol' [2.44 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/MusicVol' [350.00 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/VideoVol' [350.00 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/PicturesVol' [300.00 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/MiscVol' [60.00 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/ShareddocVol' [60.00 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/VMVol' [60.00 GiB] inherit
>>   ACTIVE            '/dev/RaidVolGrp/TorrentVol' [50.00 GiB] inherit
>
> That is output from running the Fedora LiveCD?
>
> Boot up with the CentOS 5 DVD into rescue mode, let it detect the
> existing LVMs. Go into /etc/lvm/backup and validate the info that's
> saved there and to check what CentOS sees.
>
>> sh
>
> Alexander
>
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Ok, thanks a lot for the reply

I believe this is the relevant part of /etc/lvm/backup
####################################################
RaidVolGrp {
        id = "gL5X13-q4c8-d8XJ-x6Qc-m36S-eCfp-LKnvIW"
        seqno = 22
        status = ["RESIZEABLE", "READ", "WRITE"]
        flags = []
        extent_size = 65536             # 32 Megabytes
        max_lv = 0
        max_pv = 0
        metadata_copies = 0

        physical_volumes {

                pv0 {
                        id = "BpXoKc-pQYn-zVkU-7HyH-IKLw-0IX2-Ygm2HJ"
                        device = "/dev/md1"     # Hint only

                        status = ["ALLOCATABLE"]
                        flags = []
                        dev_size = 7805081216   # 3.63452 Terabytes
                        pe_start = 384
                        pe_count = 119096       # 3.63452 Terabytes
                }
        }

        logical_volumes {

                RootVol {
                        id = "AWstlr-xw8t-FNTu-FsEA-YUxi-updp-0HfKtr"
                        status = ["READ", "WRITE", "VISIBLE"]
                        flags = []
                        segment_count = 1

                        segment1 {
                                start_extent = 0
                                extent_count = 625      # 19.5312 Gigabytes

                                type = "striped"
                                stripe_count = 1        # linear
                                stripes = [
                                        "pv0", 16250
                                ]
                        }
                }
#################################

And this is what i get when i run lvdisplay from the centos live-cd
lvdisplay
  --- Logical volume ---
  LV Name                /dev/RaidVolGrp/RootVol
  VG Name                RaidVolGrp
  LV UUID                AWstlr-xw8t-FNTu-FsEA-YUxi-updp-0HfKtr
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                50.00 GB
  Current LE             1600
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     4096
  Block device           253:2

.....

##########################
It looks like what has changes is the segment count (went from 1 to 2
segments) for the logical volume "RootVol" (and also the total number
of segments of pv0 has changed from 22 to 23 i suppose)

########################
pvdisplay fom centos live-cd
    Scanning for physical volume names
  --- Physical volume ---
  PV Name               /dev/md126
  VG Name               RaidVolGrp
  PV Size               3.63 TB / not usable 2.81 MB
  Allocatable           yes
  PE Size (KByte)       32768
  Total PE              119096
  Free PE               70058
  Allocated PE          49038
  PV UUID               BpXoKc-pQYn-zVkU-7HyH-IKLw-0IX2-Ygm2HJ


Not sure what to do from here
Should I change the /etc/lvm/backup/RaidVolGrp file to reflect the
current actuall situation? Don't see how that would help since the
file is inside the pv that can't be accessed at boot time anyway...

sh