How to restore the server using the rescue system

The Rescue System is a Linux system that runs on a RAM-Disk. A connection with
your Root-Server will look something like this (with your IP address instead of 172.17.1.1):

user@machine:~$ ssh root@172.17.1.1
Password: XXXXX
Welcome to pureserver rescue disk

If you are using a unix/linux/mac from a terminal. If you are using a windows machine you will

need to connect with an ssh client such as putty.

Remote Server Access Using Secure Shell (SSH)

From here you can partition your internal hard drive or edit incorrect settings.
The following is the standard partitioning of the internal hard drive:

If you are using hardware raid you will only see one drive.

rescue:~# fdisk -l

Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 1 123 987966 fd Linux raid autodetect
/dev/sda2 124 367 1959930 82 Linux swap / Solaris
/dev/sda4 368 19457 153340425 5 Extended
/dev/sda5 368 976 4891761 fd Linux raid autodetect
/dev/sda6 977 1585 4891761 fd Linux raid autodetect
/dev/sda7 1586 19457 143556808+ fd Linux raid autodetect
rescue:~#

If you are using software raid you will see two drives.

rescue:~# fdisk -l

Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 1 123 987966 fd Linux raid autodetect
/dev/sda2 124 367 1959930 82 Linux swap / Solaris
/dev/sda4 368 19457 153340425 5 Extended
/dev/sda5 368 976 4891761 fd Linux raid autodetect
/dev/sda6 977 1585 4891761 fd Linux raid autodetect
/dev/sda7 1586 19457 143556808+ fd Linux raid autodetect

Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 123 987966 fd Linux raid autodetect
/dev/sdb2 124 367 1959930 82 Linux swap / Solaris
/dev/sdb4 368 19457 153340425 5 Extended
/dev/sdb5 368 976 4891761 fd Linux raid autodetect
/dev/sdb6 977 1585 4891761 fd Linux raid autodetect
/dev/sdb7 1586 19457 143556808+ fd Linux raid autodetect

Disk /dev/md7: 147.0 GB, 147002097664 bytes
2 heads, 4 sectors/track, 35889184 cylinders
Units = cylinders of 8 * 512 = 4096 bytes

Disk /dev/md7 doesn't contain a valid partition table

Disk /dev/md6: 5009 MB, 5009047552 bytes
2 heads, 4 sectors/track, 1222912 cylinders
Units = cylinders of 8 * 512 = 4096 bytes

Disk /dev/md6 doesn't contain a valid partition table

Disk /dev/md5: 5009 MB, 5009047552 bytes
2 heads, 4 sectors/track, 1222912 cylinders
Units = cylinders of 8 * 512 = 4096 bytes

Disk /dev/md5 doesn't contain a valid partition table

Disk /dev/md1: 1011 MB, 1011548160 bytes
2 heads, 4 sectors/track, 246960 cylinders
Units = cylinders of 8 * 512 = 4096 bytes

Disk /dev/md1 doesn't contain a valid partition table
rescue:~#

First of all you should run a filesystem check to fix any errors in the file
structure.



For hardware raid

rescue:~# fsck -f /dev/sda1

for software raid

rescue:~# fsck -f /dev/md1

/dev/md5 or /dev/sda5, /dev/md6 or /dev/sda6, and /dev/md7 or /dev/sda7 are XFS and use

different methods to be checked.

For hardware raid

rescue:~# xfs_check /dev/sda5
rescue:~# xfs_check /dev/sda6
rescue:~# xfs_check /dev/sda7

for software raid

rescue:~# xfs_check /dev/md5
rescue:~# xfs_check /dev/md6
rescue:~# xfs_check /dev/md7

If the curser simply returns to the

rescue:~#

then there were no detectable problems. If this does report errors you will first want to

mount and umount the drives. Either mdx or sdx where x is the partition number you are

attempting to repair.

For hardware raid

rescue:~# mount /dev/sdax /mnt
rescue:~# umount /dev/sdax

for software raid

rescue:~# mount /dev/mdx /mnt
rescue:~# umount /dev/mdx

Then check the partition again. If there are still problems with 5, 6, or 7 you will need to

run xfs repairs on these partition. Using the -L option does run the risk of data loss so it

is recommended that you use this option if you have backups of the data or the data is already

irretrievable.

for hardware raid

rescue:~# xfs_repair -L /dev/sdax

for software raid

rescue:~# xfs_repair -L /dev/mdx

Now you can mount the internal hard drive into the /mnt directory and change into
the system on the partition. If you do not remember where usr, home, and var are mapped to

then mount the root partition first and check the mtab or fstab.

for hardware raid

rescue:~# mount /dev/sda1 /mnt
kjournald starting. Commit interval 5 seconds
EXT3 FS on sda1, internal journal
EXT3-fs: mounted filesystem with ordered data mode.

for software raid

rescue:~# mount /dev/md1 /mnt
kjournald starting. Commit interval 5 seconds
EXT3 FS on md1, internal journal
EXT3-fs: mounted filesystem with ordered data mode.

check to see where the usr, home, and var are assigned to

rescue:~# more /mnt/etc/mtab

or

rescue:~# more /mnt/etc/fstab

as an example of a fstab

/dev/md1 / ext3 defaults 1 1
/dev/sda2 none swap sw
/dev/sdb2 none swap sw
/dev/md5 /usr xfs defaults 0 2
/dev/md7 /var xfs defaults,usrquota 0 2
/dev/md6 /home xfs defaults,usrquota 0 2
devpts /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /tmp tmpfs defaults 0 0


Then mount the other partitions. The below example commands are based on the partitions from

the example fstab above. You will need to match 5, 6, or 7 to usr, home, and var based on your

fstab or mtab. If you are using hardware raid it will be sdax instead of mdx where x is the

partition number.

rescue:~# mount /dev/md5 /mnt/usr
rescue:~# mount /dev/md6 /mnt/home
rescue:~# mount /dev/md7 /mnt/var

One of the things you can check here is:

ensure that the partitions are not full with

rescue:~# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/ram0 252M 218M 34M 87% /
tmpfs 998M 4.0K 998M 1% /dev/shm
/dev/md1 950M 137M 765M 16% /mnt
/dev/md5 4.7G 2.1G 2.6G 46% /mnt/usr
/dev/md6 4.7G 4.4M 4.7G 1% /mnt/home
/dev/md7 221G 111M 221G 1% /mnt/var

if any of these

/dev/md1 950M 137M 765M 16% /mnt
/dev/md5 4.7G 2.1G 2.6G 46% /mnt/usr
/dev/md6 4.7G 4.4M 4.7G 1% /mnt/home
/dev/md7 221G 111M 221G 1% /mnt/var

are at or near 100% this will cause problems and you will want to remove data to create more

free space. You can search for large files with the find command. So if the /mnt/var

partition is full you would use

rescue:~# find /mnt/var -size +1000M

to search for files larger then 1000MB. If you do not find anything decrease the size to 750M

and look again. In many situations it is log files that create these problems. You can move

large log files to your ftp backup space using ftp.

then chroot into the mounted operating system.

rescue:~# chroot /mnt

Now you can repair and/or configure your Root-Server now that you are in /mnt as if you were

logged into the machine under normal conditions. Note: most of the services will be stopped

that would normally be running.

So if you need to make a proper database dump of your mysql databases you could start mysql

rescue:~# /etc/init.d/mysqld start



After you have finished restoring your root server you need to execute the
following commands to restart your Root-Server:

to exit the chroot environment

rescue:~# exit

to umount your partitions

rescue:~# umount -al

Do not forget to unmount your internal hard drive after the restore and BEFORE you
restart the server. Also remember to change your Root-Server back to normal boot
mode from your Control Panel. You have the option of rebooting from inside the recovery tool

or just changing the boot image by either selecting the reboot now option or not. If you do

not select the reboot now option it will only change the boot mode.


rescue:~# shutdown -r now