btextract - Extracts the file systems from tape in singleuser
mode in memory
The btextract command is a shell script that restores file
systems from tapes that contain the bootable Standalone
System (SAS) kernel. The SAS kernel is created using the
btcreate utility. You can perform a default restore or an
advanced restore operation.
Use the default restore option when you want to duplicate
the customized system on more than one machine of the same
hardware platform type. When you perform a default
restore, you cannot specify which disk partitions to use.
Instead, the btextract command restores file systems using
the disk partition information gathered during the btcreate
session. The restore operation overwrites all existing
information on the target drive.
To perform a default restore operation, the disk configuration
of the system you backed up must be the same as the
system you are restoring. Use the diskconfig GUI or the
disklabel and newfs commands to prepare a disk to receive
the extracted tape contents.
During an advanced restore operation, the btextract command
prompts you to enter the name of a disk partition.
The file systems are restored to the specified partition.
During an advanced restore operation, the btextract command
assigns the b partition of the root disk as the swap
You cannot restore a file system that is more than 100%
full to a partition of the same size as the original partition.
During the restore of the UFS file system, the
/sbin/restore command adds a new file named
restoresymtable. The presence of this restoresymtable file
can make the restored file system larger than the source
partition size listed in the output from the /sbin/disklabel
For example, on the source system, the disklabel shows the
target h partition to be:
h: 86758 1212416 4.2BSD
The UFS file system is as follows:
Filesystem 512-blocks Used Available Capacity
Mounted on /dev/dsk8h 83812 83786 0
The file system is 112% full. This file system cannot be
restored on the target file system of 86758 blocks
(512-byte blocks), because the following file is created
by the /sbin/restore command.
-rw-r--r-- 1 root system 27368 Jul 2 09:33
The /sbin/restore command creates a restoresymtable file
that exceeds the 112% range. The solution is to use a
partition of about 86996 (512-byte blocks), about 3.8%
larger than the actual file size.
Using btextract [Toc] [Back]
To use the btextract utility, place the system in a halt
state, initialize the system, then boot from the tape as
follows: >>> init >>> show dev >>> boot -fl "nc" MKA500
In the preceding example, the show dev command provides
the device name under BOOTDEV, and MKA500 is the BOOTDEV.
After the initial boot is complete, the shell invokes the
btextract command. If you created a
/usr/lib/sabt/sbin/custom_install.sh script during the
btcreate session, the btextract command invokes the custom_install.sh
script before exiting. See btcreate for
You can optionally label disks using your own disklabel
script. If a customized disk labeling script is not present,
the btextract command labels the disks in the usual
manner. A customized disklabel script has the following
restrictions: It must be located in the /usr/lib/sabt/etc
directory. It must be named custom_disklabel_file.
After the btextract command completes, you must shut down
the system, then reboot the system from the restored disk
as follows: # shutdown -h now >>> boot DKA100
In the preceding example, DKA100 is the BOOTDEV.
Creating a Custom Prerestore File [Toc] [Back]
When you boot a system using bootable tape, the btextract
command prompts you to create an answer file that provides
the minimum information needed to complete the boot and
restore operation. This custom_prerestore file is a text
file located in the /usr/lib/sabt/etc directory. The minimum
contents are as follows:
TAPE_USED="/dev/tape/tape0_d1" #Tape drive used
RESTORE_TYPE="no" #Restore type yes=DEFAULT
no=ADVANCED SPART="b" #Primary Swap
You can also create the custom_prerestore file manually,
and use it to fully automate the recovery procedure. The
file can contain the following entries: INTERACTIVE=["yes
| no"] - Specifies whether the session is to be interactive
or not. A yes entry forces an interactive session. A
typical entry is as follows: INTERACTIVE="no"
TAPE_USED="device_special_file" - Specifies the device
special file name of the tape drive from which the standalone
kernel was booted. A typical entry is as follows:
TDRIVE="/dev/tape/tape0_d1" RESTORE_TYPE=["yes | no"] -
Specifies whether this is to be a default (yes) or an
advanced restore (no). A typical entry is as follows:
RESTORE_TYPE="no" SDRIVE="disk_type device name" -
Specifies the primary swap disk drive. This entry requires
the following parameters: disk_type - The disk device
model, such as HB00931B93 . You can obtain this information
by using the following command: # hwmgr -show component
| grep iomap
The hardware identifier is shown under the HWID
column in the command output. You use this information
to determine the device name of a disk.
device name - The device instance, such as dsk8.
This information is part of the device special file
name assigned to the disk. You can obtain this
information by using the following command: # hwmgr
SCSI DEVICE DEVICE DRIVER NUM
DEVICE FIRST HWID: DEVICEID HOSTNAME TYPE SUBTYPE
OWNER PATH FILE VALID PATH
32: 0 cymro disk none 2 1
In the preceding command output, the entry under
the HWID column identifies the disk that you chose
by using the show component option. The HWID is 32
in this example.
A typical entry is as follows: SDRIVE="HB00931B93
dsk13" SPART="partition_id" - Specifies the primary
swap partition on the restored disk. A typical
entry is as follows: SPART="b" DDRIVE_1="disk_type
device name" - Specifies the root file system disk
drive. A typical entry is as follows:
DDRIVE_1="RZ1CB-CS dsk13" PPART_1="partition_id" -
Specifies the root file system partition. A typical
entry is as follows: PPART="a" DDRIVE_2="disk_type
device name" - Specifies the disk drive used for
the /usr file system. A typical entry is as follows:
DDRIVE_2="HB00931B93 dsk11" PPART_1="partition_id"
- Specifies the /usr file system partition.
A typical entry is as follows: PPART="g"
DDRIVE_N="disk_type device name" Specifies the
disks used for each additional file system that is
restored, where N is an integer ranging from 3 to
the total number of file systems to be restored.
Use entries similar to the following:
DDRIVE_3="HB00931B93 dsk12" PPART_N="partition_id "
Specifies the partitions used for each additional
file system that is restored, where N is an integer
ranging from 3 to the total number of filesystems
to be restored. Use entries similar to the following:
To insert comments in the custom prerestore file, preceded
each comment line with the number symbol (#).
Success. An error occurred.
Log of the btextract process in memory Copy of the btextract
process on the restored root file system Script used
to customize the restored image A custom disklabel file
read by btextract
Commands: addvol(8), btcreate(8), df(1), disklabel(8),
lmf(8), mkfdmn(8), mkfset(8), newfs(8), restore(8), sh(1),
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