Emergency Restore Procedure

Before the Disaster

There are only four steps that you need to perform in preparation for any disaster that may occur and you want to restore from your "private" backup. At this point anterprise-level backup may or may not exist but you own backup should cover the at least OS and some important data.

1. First, save mbr  from each of your disks
2. (e.g. bsdlabel da0 | lpr), your file system table (/etc/fstab) and all boot messages, two copies of each.
3. Second, create recovery USB drive. 32GB is enough for all system files plus some user directories. 128GB 9max size of FIT dirves) often can store most important user directory and recent data as well. You need also list of your active devices.  The easiest way to check is to reboot your machine with the boot USB drive in the USB drive drive and check the boot messages. If all your devices are listed and functional, skip on to step three.
4. Third, create backups regularly. Any changes that you make after your last backup may be irretrievably lost. Label and write-protect the backup media if you use multiple flash or USB drives. 
5. Fourth, test the your recovery USB and  backups storage. Make notes of the procedure. Store these notes . You will be so distraught or tired when restoring that only having accurate notes may prevent you from destroying your backup and complication the situation (for example in place of tar xvf /dev/sdc1, you might accidentally type tar cvf /dev/sdc1 and over-write your backup).

#!/bin/sh
#
# create a restore USB drive
#
# format the USB drive
#
PATH=/bin:/sbin:/usr/sbin:/usr/bin

#
# mount the new USB drive
#
mount /dev/sdc /mnt

#
# create required directories
#
mkdir /mnt/dev
mkdir /mnt/bin
mkdir /mnt/sbin
mkdir /mnt/etc
mkdir /mnt/root
mkdir /mnt/mnt          # for the root partition
mkdir /mnt/tmp
mkdir /mnt/var

#
# populate the directories
#
if [ ! -x /sys/compile/MINI/kernel ]
then
     cat << EOM
The MINI kernel does not exist, please create one.
Here is an example config file:
#
# MINI -- A kernel to get FreeBSD onto a disk.
#
machine         "i386"
cpu             "I486_CPU"
ident           MINI
maxusers        5

options         INET                    # needed for _tcp _icmpstat _ipstat
                                        #            _udpstat _tcpstat _udb
options         FFS                     #Berkeley Fast File System
options         FAT_CURSOR              #block cursor in syscons or pccons
options         SCSI_DELAY=15           #Be pessimistic about Joe SCSI device
options         NCONS=2                 #1 virtual consoles
options         USERCONFIG              #Allow user configuration with -c XXX

config          kernel  root on da0 swap on da0 and da1 dumps on da0

device          isa0
device          pci0

device          fdc0    at isa? port "IO_FD1" bio irq 6 drq 2 vector fdintr
device          fd0 at fdc0 drive 0

device          ncr0

device          scbus0

device          sc0 at isa? port "IO_KBD" tty irq 1 vector scintr
device          npx0    at isa? port "IO_NPX" irq 13 vector npxintr

device          da0
device          da1
device          da2

device          sa0

pseudo-device   loop            # required by INET
pseudo-device   gzip            # Exec gzipped a.out's
EOM
     exit 1
fi

cp -f /sys/compile/MINI/kernel /mnt

gzip -c -best /sbin/init > /mnt/sbin/init
gzip -c -best /sbin/fsck > /mnt/sbin/fsck
gzip -c -best /sbin/mount > /mnt/sbin/mount
gzip -c -best /sbin/halt > /mnt/sbin/halt
gzip -c -best /sbin/restore > /mnt/sbin/restore

gzip -c -best /bin/sh > /mnt/bin/sh
gzip -c -best /bin/sync > /mnt/bin/sync

cp /root/.profile /mnt/root

chmod 500 /mnt/sbin/init
chmod 555 /mnt/sbin/fsck /mnt/sbin/mount /mnt/sbin/halt
chmod 555 /mnt/bin/sh /mnt/bin/sync
chmod 6555 /mnt/sbin/restore

#
# create minimum file system table
#
cat > /mnt/etc/fstab <<EOM
/dev/fd0a    /    ufs    rw  1  1
EOM

#
# create minimum passwd file
#
cat > /mnt/etc/passwd <<EOM
root:*:0:0:Charlie &:/root:/bin/sh
EOM

cat > /mnt/etc/master.passwd <<EOM
root::0:0::0:0:Charlie &:/root:/bin/sh
EOM

chmod 600 /mnt/etc/master.passwd
chmod 644 /mnt/etc/passwd
/usr/sbin/pwd_mkdb -d/mnt/etc /mnt/etc/master.passwd

#
# umount the USB drive and inform the user
#
/sbin/umount /mnt
echo "The USB drive has been unmounted and is now ready."

NEWS CONTENTS

• 200208 : Linux sfdisk command can make a backup of the primary and extended partition table ( )

Old News ;-)

Linux sfdisk command can make a backup of the primary and extended partition table

Linux sfdisk command can make a backup of the primary and extended partition table as follows. It creates a file that can be read in a text editor, or this file can be used by sfdisk to restore the primary/extended partition table. To back up the partition table /dev/sda, enter:
# sfdisk -d /dev/sda > /tmp/sda.bak
To restore, enter:
# sfdisk /dev/sda < /tmp/sda.bak
The above command will restore extended partitions.

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Last modified: March, 12, 2019