On Sun Ultra systems, set up with an encapsulated rootdg,  mirrored to an alternate device, it is sometimes necessary to determine exactly which half of the mirror the machine is booted off. This can be done in multi-user mode by executing the following command.
Note: This example is from a Sun E3500 with two internal Sun fiber disks as the encapsulated root drives.

# prtconf -vp | grep bootpath
bootpath:  '/sbus@3,0/SUNW,socal@d,10000/sf@0,0/ssd@w2100002037590098,0:a'

During root disk encapsulation, the system's nvramrc is modified with device aliases which expand to the fully qualified device path of each encapsulated bootable root disk. These aliases are only usable once the user has set the eeprom variable, use-nvramrc?, to true. This can be done as root by executing either of the following commands from a Solaris prompt:

# /usr/sbin/eeprom use-nvramrc?=true

or

# /etc/vx/bin/vxeeprom enable

However, the aliases are not valid until the next system reset. Therefore the user is encouraged to set eeprom variables while at the eeprom ok> prompt, prior to system initialization. Example eeprom session:

ok> printenv use-nvramrc?
use-nvramrc? =    false
ok> setenv use-nvramrc?  true
ok> setenv auto-boot? false               # keep system from booting to Solaris when run reset next
ok> reset                                 # reset eeprom only
ok> devalias                              # show Solaris aliases plus the Volume Manager generated devaliases from nvramrc.

vx-disk01                    /sbus@3,0/SUNW,socal@d,10000/sf@0,0/ssd@w21000020374fe71f,0:a'
vx-rootdisk                  /sbus@3,0/SUNW,socal@d,10000/sf@0,0/ssd@w2100002037590098,0:a'
ok> setenv auto-boot? true
ok> reset                                 # system will now continue booting to default boot-device

Once booted, the new devaliases can be seen in the prtconf output.

# prtconf -vp | grep vx
vx-disk01:  '/sbus@3,0/SUNW,socal@d,10000/sf@0,0/ssd@w21000020374fe71f,0:a'
vx-rootdisk:  '/sbus@3,0/SUNW,socal@d,10000/sf@0,0/ssd@w2100002037590098,0:a'

# prtconf -vp | grep boot-device
boot-device:  '/sbus@3,0/SUNW,socal@d,10000/sf@0,0/ssd@w2100002037590098,0'

- shows the boot device equal to the devalias vx-rootdisk. boot-device is another eeprom setting which is set to the default boot path (or devalias).

To boot off the alternate root disk from the ok> prompt, run:

ok> boot vx-disk01

- to load Solaris from the alternate root, subsequently changing the value of bootpath.

Converting this path to the c#/t#/d# device can be done either by running format at the root prompt and searching for the path, or listing the /device tree and grep'ing for this path.