2013-08-14

independent Raspberry Pi

The Raspberry Pi is great, but by default it needs usb for power and utp for network.

Luckily there is the Smart Power Base to provide power and the Netgear (I use the wna1100 for obvious reasons) for wireless, both making the Pi a lot more independent.


2013-08-04

Recovering lvm2 on degraded mdadm raid 1

An mdadm raid 1 had one disk crash, the other was moved to a new computer (/dev/sdb2).

Step 1: Does fdisk see the disk: yes

root@debian6~# fdisk -l /dev/sdb

Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00060f19

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         254     2040254+  83  Linux
/dev/sdb2             255      121602   974722329   83  Linux 
 

Step 2: Gently look with fsck, yes it is part of mdadm
  
root@debian6~# fsck -n /dev/sdb2
fsck from util-linux-ng 2.17.2
fsck: fsck.linux_raid_member: not found
fsck: Error 2 while executing fsck.linux_raid_member for /dev/sdb2


Step 3: Let's see what mdadm says

root@debian6~# mdadm --examine /dev/sdb2
/dev/sdb2:
          Magic : a92b4efc
        Version : 1.0
    Feature Map : 0x0
     Array UUID : e8221214:354aaaf1:e9e15d78:075bfc18
           Name : storage:1
  Creation Time : Thu May  6 20:00:16 2010
     Raid Level : raid1
   Raid Devices : 2

 Avail Dev Size : 1949444384 (929.57 GiB 998.12 GB)
     Array Size : 1949444384 (929.57 GiB 998.12 GB)
   Super Offset : 1949444640 sectors
          State : clean
    Device UUID : 0c265a25:cc3f2ddd:ae7a1511:f447c74e

    Update Time : Tue May  1 23:09:11 2012
       Checksum : 498b9bd4 - correct
         Events : 33039098


   Device Role : Active device 0
   Array State : A. ('A' == active, '.' == missing) 


Step 4: Let's fix the md device

root@debian6~# mdadm --assemble --scan
mdadm: /dev/md/storage:1 has been started with 1 drive (out of 2).
mdadm: /dev/md/0_0 has been started with 1 drive (out of 2).

root@debian6~# cat /proc/mdstat 
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
md126 : active (auto-read-only) raid1 sdb1[0]
      2040128 blocks [2/1] [U_]
      
md127 : active (auto-read-only) raid1 sdb2[0]
      974722192 blocks super 1.0 [2/1] [U_]
      
unused devices:  

root@debian6~# fdisk -l
....
Disk /dev/md127: 998.1 GB, 998115524608 bytes
2 heads, 4 sectors/track, 243680548 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/md127 doesn't contain a valid partition table 


Step 5: Gently look with mount and lvs/pvs

root@debian6~# mount /dev/md127 /mnt
mount: unknown filesystem type 'LVM2_member'

root@debian6~# lvs
  No volume groups found
root@debian6~# pvs


Step 6: Fix the lvm2 device

root@debian6~# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "md1_vg" using metadata type lvm2

root@debian6~# vgs
  VG     #PV #LV #SN Attr   VSize   VFree
  md1_vg   1   1   0 wz--n- 929.57g    0 
root@debian6~# pvs
  PV         VG     Fmt  Attr PSize   PFree
  /dev/md127 md1_vg lvm2 a-   929.57g    0 
root@debian6~# lvs
  LV      VG     Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  md1vol1 md1_vg -wi--- 929.57g 
 
 
Step 7: The lvm2 device is not activated, yet


root@debian6~# lvdisplay 
  --- Logical volume ---
  LV Name                /dev/md1_vg/md1vol1
  VG Name                md1_vg
  LV UUID                qSpslc-nO70-8jjX-5lBl-ge20-fFdR-dSEnWk
  LV Write Access        read/write
  LV Status              NOT available
  LV Size                929.57 GiB
  Current LE             475938
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto 
 
 
Step 8: Activate lvm2 device and mount


root@debian6~# vgchange -a y
  1 logical volume(s) in volume group "md1_vg" now active

root@debian6~# mount /dev/md1_vg/md1vol1 /mnt

root@debian6~# mount | grep mnt
/dev/mapper/md1_vg-md1vol1 on /mnt type xfs (rw)