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btextract(8)
NAME
btextract - Extracts the file systems from tape in single-user mode in
memory
SYNOPSIS
/usr/sys/bin/btextract
DESCRIPTION
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.
Note
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.
Note
During an advanced restore operation, the btextract command assigns
the b partition of the root disk as the swap partition.
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 command.
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 0 112% /bootable
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 restoresymtable
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
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 more information.
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
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 drive partition
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 -show scsi
SCSI DEVICE DEVICE DRIVER NUM DEVICE FIRST
HWID: DEVICEID HOSTNAME TYPE SUBTYPE OWNER PATH FILE VALID PATH
----------------------------------------------------------------------
32: 0 cymro disk none 2 1 dsk0 [0/0/0]
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:
PPART_3="c"
To insert comments in the custom prerestore file, preceded each comment
line with the number symbol (#).
RETURN VALUES
0 (zero)
Success.
>0 An error occurred.
FILES
/var/adm/btextract.log
Log of the btextract process in memory
/btextract.log
Copy of the btextract process on the restored root file system
/usr/lib/sabt/sbin/custom_install.sh
Script used to customize the restored image
/usr/lib/sabt/etc/custom_disklabel_file
A custom disklabel file read by btextract
SEE ALSO
Commands: addvol(8), btcreate(8), df(1), disklabel(8), lmf(8), mkfdmn(8),
mkfset(8), newfs(8), restore(8), sh(1), vrestore(8)
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Index for
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Alphabetical
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