Creating a bootable disk from the OS mirror

There are several situations when the administrator wants to break the link between the root disk and the root mirror device, while retaining the ability to boot from the mirror. For example, the administrator would like to make changes to the operating system which may be difficult to reverse (eg. applying a patch cluster or upgrading the operating system). By creating a separate bootable mirror prior to the maintenance, the administrator would retain the option of booting from the mirror if the maintenance did not go as well as expected.

The following sequence of steps assumes that the system starts as a standard encapsulated boot disk and associated mirror device.

# vxprint -ht
Disk group: rootdg

DG NAME         NCONFIG      NLOG     MINORS   GROUP-ID
DM NAME         DEVICE       TYPE     PRIVLEN  PUBLEN   STATE
RV NAME         RLINK_CNT    KSTATE   STATE    PRIMARY  DATAVOLS  SRL
RL NAME         RVG          KSTATE   STATE    REM_HOST REM_DG    REM_RLNK
V  NAME         RVG          KSTATE   STATE    LENGTH   READPOL   PREFPLEX UTYPE
PL NAME         VOLUME       KSTATE   STATE    LENGTH   LAYOUT    NCOL/WID MODE
SD NAME         PLEX         DISK     DISKOFFS LENGTH   [COL/]OFF DEVICE   MODE
SV NAME         PLEX         VOLNAME  NVOLLAYR LENGTH   [COL/]OFF AM/NM    MODE
DC NAME         PARENTVOL    LOGVOL
SP NAME         SNAPVOL      DCO

dg rootdg       default      default  0        1035385242.1025.pegasus

dm rootdisk     c0t0d0s2     sliced   3359     17693759 -
dm rootmirror   c0t1d0s2     sliced   3359     17690400 -

sd rootdiskPriv -            rootdisk 13423200 3359     PRIVATE   c0t0d0   ENA

v  rootvol      -            ENABLED  ACTIVE   13423200 ROUND     -        root
pl rootvol-01   rootvol      ENABLED  ACTIVE   13423200 CONCAT    -        RW
sd rootdisk-B0  rootvol-01   rootdisk 13423199 1        0         c0t0d0   ENA
sd rootdisk-02  rootvol-01   rootdisk 0        13423199 1         c0t0d0   ENA
pl rootvol-02   rootvol      ENABLED  ACTIVE   13423200 CONCAT    -        RW
sd rootmirror-01 rootvol-02  rootmirror 0      13423200 0         c0t1d0   ENA

v  swapvol      -            ENABLED  ACTIVE   2096640  ROUND     -        swap
pl swapvol-01   swapvol      ENABLED  ACTIVE   2096640  CONCAT    -        RW
sd rootdisk-01  swapvol-01   rootdisk 13426559 2096640  0         c0t0d0   ENA
pl swapvol-02   swapvol      ENABLED  ACTIVE   2096640  CONCAT    -        RW
sd rootmirror-02 swapvol-02  rootmirror 13423200 2096640 0        c0t1d0   ENA

v  var          -            ENABLED  ACTIVE   2100000  ROUND     -        fsgen
pl var-01       var          ENABLED  ACTIVE   2100000  CONCAT    -        RW
sd rootdisk-04  var-01       rootdisk 15523199 2100000  0         c0t0d0   ENA
pl var-02       var          ENABLED  ACTIVE   2100000  CONCAT    -        RW
sd rootmirror-03 var-02      rootmirror 15519840 2100000 0        c0t1d0   ENA

1. Record which slices of rootmirror are allocated for the Veritas public and private regions (3 and 4 in our case):

   # vxdisk list rootmirror | egrep "private|public"
   flags:     online ready private autoconfig autoimport imported
   public:    slice=3 offset=1 len=17690400
   private:   slice=4 offset=1 len=3359
   

2. Disassociate and then remove all of the operating system plexes on the mirror device "rootmirror":

   # vxplex -g rootdg dis rootvol-02 swapvol-02 var-02
# vxedit -g rootdg -r rm rootvol-02 swapvol-02 var-02

3. Remove the rootmirror disk from rootdg

   # vxdg -g rootdg rmdisk rootmirror

4. Run a filesystem check on each of the ufs filesystem slices on c0t1d0 (formerly identified as "rootmirror"):

   # fsck -F ufs -y /dev/rdsk/c0t1d0s0
# fsck -F ufs -y /dev/rdsk/c0t1d0s4

5. Update the /etc/system and /etc/vfstab files on c0t1d0 so that there are no references to volume manager devices:

   # mount /dev/dsk/c0t1d0s0 /mnt
   # cp /mnt/etc/system /mnt/etc/system.orig
   # vi /mnt/etc/system
   

   Change the lines:

   rootdev:/pseudo/vxio@0:0
   set vxio:vol_rootdev_is_volume=1
   

   to:

   * rootdev:/pseudo/vxio@0:0
   * set vxio:vol_rootdev_is_volume=1
   

6. Restore the pre-VxVM version of the vfstab file. Note that the vxinstall process makes a backup copy of the original vfstab file named vfstab.prevm. We'll make use of that backup now:

   # cp /mnt/etc/vfstab /mnt/etc/vfstab.vm
   
   # cp /mnt/etc/vfstab.prevm /mnt/etc/vfstab
   

   Edit the /mnt/etc/vfstab file so that it references c0t1 instead of c0t0:

   # cat /mnt/etc/vfstab
   #device         device          mount           FS      fsck    mount   mount
   #to mount       to fsck         point           type    pass    at boot options
   #
   #/dev/dsk/c1d0s2 /dev/rdsk/c1d0s2 /usr          ufs     1       yes     -
   fd                  -                  /dev/fd fd      -       no      -
   /proc               -                  /proc   proc    -       no      -
   /dev/dsk/c0t1d0s1   -                  -       swap    -       no      -
   /dev/dsk/c0t1d0s0   /dev/rdsk/c0t1d0s0 /       ufs     1       no      logging
   /dev/dsk/c0t1d0s6   /dev/rdsk/c0t1d0s6 /var    ufs     1       no      logging
   swap                -                  /tmp    tmpfs   -       yes     -
   

   Note that the slices used for the various partitions may be different on the mirror disk than they were on the original root disk prior to encapsulation! When it initialized the rootmirror device, Veritas probably used slices 3 and 4 for the private and public regions, and relocated other slices elsewhere on the mirror. For example, if c0t0d0s4 was the original pre-encapsulated /var, then it is possible that new location of /var on the mirror device is c0t1d0s6, for example. You will have to carefully examine the partition table of c0t1d0 to determine how Veritas managed the slice allocation process on the mirror and update the /mnt/etc/vfstab file accordingly.

7. If the install-db file exists, the VxVM daemons will not start on bootup:

   # touch /mnt/etc/vx/reconfig.d/state.d/install-db

8. The root-done file indicates that the root disk has been encapsulated. Remove it now:

   # rm /mnt/etc/vx/reconfig.d/state.d/root-done

9. Finally, unmount the root filesystem and reboot:

   # cd /; umount /mnt

10. Zero out the private and public regions on c0t1d0:

    # format
    Searching for disks...done
    
    
    AVAILABLE DISK SELECTIONS:
           0. c0t0d0 
              /pci@1f,4000/scsi@3/sd@0,0
           1. c0t1d0 
              /pci@1f,4000/scsi@3/sd@1,0
    Specify disk (enter its number): 1
    selecting c0t1d0
    [disk formatted]
    
    ...
    partition> print
    Current partition table (original):
    Total disk cylinders available: 5266 + 2 (reserved cylinders)
    
    Part      Tag    Flag     Cylinders        Size            Blocks
      0       root    wm       1 - 3995        6.40GB    (3995/0/0) 13423200
      1       swap    wu    3996 - 4620        1.00GB    (625/0/0)   2100000
      2     backup    wm       0 - 5265        8.44GB    (5266/0/0) 17693760
      3          -    wu       0 -    0        1.64MB    (1/0/0)        3360
      4          -    wu       1 - 5265        8.44GB    (5265/0/0) 17690400
      5 unassigned    wm       0               0         (0/0/0)           0
      6        var    wm    4621 - 5245        1.00GB    (625/0/0)   2100000
      7 unassigned    wm       0               0         (0/0/0)           0
    
    partition> 3
    Part      Tag    Flag     Cylinders        Size            Blocks
      3          -    wu       0 -    0        1.64MB    (1/0/0)        3360
    
    Enter partition id tag[unassigned]: 
    Enter partition permission flags[wu]: 
    Enter new starting cyl[0]: 
    Enter partition size[3360b, 1c, 1.64mb, 0.00gb]: 0
    partition> 4
    Part      Tag    Flag     Cylinders        Size            Blocks
      4          -    wu       1 - 5265        8.44GB    (5265/0/0) 17690400
    
    Enter partition id tag[unassigned]: 
    Enter partition permission flags[wu]: 
    Enter new starting cyl[1]: 0
    Enter partition size[17690400b, 5265c, 8637.89mb, 8.44gb]: 0
    partition> p
    Current partition table (unnamed):
    Total disk cylinders available: 5266 + 2 (reserved cylinders)
    
    Part      Tag    Flag     Cylinders        Size            Blocks
      0       root    wm       1 - 3995        6.40GB    (3995/0/0) 13423200
      1       swap    wu    3996 - 4620        1.00GB    (625/0/0)   2100000
      2     backup    wm       0 - 5265        8.44GB    (5266/0/0) 17693760
      3 unassigned    wu       0               0         (0/0/0)           0
      4 unassigned    wu       0               0         (0/0/0)           0
      5 unassigned    wm       0               0         (0/0/0)           0
      6        var    wm    4621 - 5245        1.00GB    (625/0/0)   2100000
      7 unassigned    wm       0               0         (0/0/0)           0
    
    partition> label
    Ready to label disk, continue? y
    
    partition> quit
    
    

11. Shutdown the operating system and confirm that you can boot from the former mirror device.

Having broken it off and booted successfully from the mirror, reboot to the encapsulated rootdisk and perform the maintenance, confident that you have a pre-patched image of the operating system available "just in case".