Working with the Linux Rescue System (Hardware RAID)

For Dedicated Server managed in the Cloud Panel

In this article, you will learn how to use your Dedicated Server's Linux rescue system to back up the data of your server.

The software required to manage each RAID controller is installed by default. If necessary, you can download the software for the respective controller here:

Broadcom Hardware RAID Controller

https://www.broadcom.com/support/download-search

Dell Hardware RAID Controller

https://www.dell.com/support/home/de-de?app=products

To check which hardware controller is installed in your server, enter the following command:

lspci|grep RAID

Example:

rescue:~# lspci|grep RAID
02:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID Tri-Mode SAS3408 (rev 01)

Use the commands below to access hardware raid and configuration information:

Broadcom Controller

You can find further information here:

12Gb/s MegaRAID Tri-Mode StorCLI User Guide

DELL PERC Controller

You can find further information here:

Dell EMC PowerEdge RAID Controller CLI Reference Guide

This is how you display the partitioning:

• To display a list of the file systems and identify the file system, enter the command df -h. The abbreviation df stands for disk free. The parameter -h allows you to display the number of occupied blocks in gigabytes, megabytes or kilobytes in a machine-readable form.

  rescue:~# df -h

  Example:

  rescue:~# df -h
  Filesystem      Size  Used Avail Use% Mounted on
  /dev/root       630M  560M   71M  89% /
  devtmpfs         16G     0   16G   0% /dev
  tmpfs            16G     0   16G   0% /dev/shm
  tmpfs            16G   14M   16G   1% /run
  tmpfs           5.0M     0  5.0M   0% /run/lock
  tmpfs            16G     0   16G   0% /sys/fs/cgroup

• To list the existing disks, partitions and logical volumes, enter the command fdisk -l. fdisk is a command line utility for partitioning disks. This program lets you display, create or delete partitions.

  rescue:~# fdisk -l

  The following example lists information about the hard disks, partitions, and logical volumes of a server with hardware raid:

  rescue:~# fdisk -l
  Disk /dev/ram0: 640 MiB, 671088640 bytes, 1310720 sectors
  Units: sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 4096 bytes
  I/O size (minimum/optimal): 4096 bytes / 4096 bytes
  
  
  Disk /dev/sda: 1.8 TiB, 1999844147200 bytes, 3905945600 sectors
  Units: sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  Disklabel type: gpt
  Disk identifier: DCBF9911-237E-47D0-BA51-D3802287C521
  
  
  Device        Start        End    Sectors  Size Type
  /dev/sda1      2048       6143       4096    2M BIOS boot
  /dev/sda2      6144   58593279   58587136   28G Linux filesystem
  /dev/sda3  58593280   78125055   19531776  9.3G Linux swap
  /dev/sda4  78125056 3905943551 3827818496  1.8T Linux LVM
  
  
  Disk /dev/mapper/vg00-usr: 10 GiB, 10737418240 bytes, 20971520 sectors
  Units: sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  
  
  Disk /dev/mapper/vg00-var: 10 GiB, 10737418240 bytes, 20971520 sectors
  Units: sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  
  
  Disk /dev/mapper/vg00-home: 10 GiB, 10737418240 bytes, 20971520 sectors
  Units: sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes

  Make a note of the paths of the logical volumes and partitions. In this example, the partition is /dev/sda2 and the logical volumes are /dev/mapper/vg00-usr, /dev/mapper/vg00-var, and /dev/mapper/vg00-home.

Usually all logical volumes are started when the rescue system is started. If these are not active, you can start the logical volumes manually. To do this, enter the following commands:

rescue:~# pvscan
rescue:~# vgscan
rescue:~# vgchange -a y

Before you mount the partition or logical volume, you should check the file system for consistency with a File System Check (FSCK). 

To check a partition or logical volume using the File System Check, type the following command:

Partition

rescue:/# fsck -f /PATH/PARTITION

Logical Volume

rescue:/# fsck -f /PATH/LOGICAL_VOLUME

The following example checks the file system of the sda2 partition:

rescue:~# fsck -f /dev/sda2
fsck from util-linux 2.29.2
e2fsck 1.43.4 (31-Jan-2017)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
root: 3989/1831424 files (1.9% non-contiguous), 206934/7323392 blocks

To mount a partition or logical volume:

• To create the directory in which to mount the partition or logical volume, type the following command:

  rescue:/# mkdir /mnt/DIRECTORY

  Examples:
  
  Logical Volume

  rescue:/# mkdir /mnt/usr

  Partition

  rescue: /# mkdir /mnt/sda2

• To mount the partition or logical volume, type the following command:

  rescue:/# mount /PATH/Partition /mnt/DIRECTORY

  or

  rescue:/# mount /PATH/LOGICAL_VOLUME /mnt/DIRECTORY

  Examples:
  
  Mounting a partition:

  rescue:/# mount /dev/sda2 /mnt/sda2

  Mounting a Logical Volume:

  rescue:/# mount /dev/mapper/vg00-home /mnt/home

You have the following options to back up the data of your servers:

• You save the data on your local computer using WinSCP.

• You save the data on another server using Secure Copy.

• You save the data on a local computer using Secure Copy.

After backing up your data, you can install a new image on the server or restore a backup of your system. Then you can copy the saved data to the server.

Backup Data to a Local Computer Using WinSCP

If you are using WinSCP to back up your data to a local computer, you can select the desired data and drag and drop it to a directory on your local computer. 

Copy data to another Server using Secure Copy

Secure Copy is an encrypted data transfer protocol based on Secure Shell. To transfer the data, enter the following command in the shell:

scp -r /PATH/LIST username@IP-ADRESS:/PATH/DESTINATION LIST

Example:

scp -r /mnt root@82.165.69.130:/home/backup

Save data from a local computer with Linux operating system

The following command allows you to save a directory located on the server to your local computer:

scp remote_username@SERVERIP:/DIRECTORY_FROM_COPY /COPY_LOCAL_DIRECTORY

Example:

[root@localhost ~]# scp root@217.160.44.208:/home /opt/backup

In the example above, the /home directory is copied to the /opt/backup directory located on the local computer.

To save a single file on your local computer, type the following command:

scp remote_username@SERVERIP:/remote/DIRECTORY_ON_THE_SERVER/FILENAME.txt /local_directory 

Example:

[root@localhost ~]# scp root@217.160.44.208:/remote/home/test.txt /TEMP 

Use the following command to copy a directory that is on your local computer to your server:

scp -r /LOKAL DIRECTORY remote_username@SERVERIP:/DIRECTORY_ON_THE_SERVER

Example:

[root@localhost ~]# scp -r /home/backup root@217.160.44.208:/home

To copy a single file, enter the following command:

scp -r /DIRECTORY/FILENAME remote_username@SERVERIP:/DIRECTORY_ON_THE_SERVER

Example:

[root@localhost ~]# scp -r /home/test.txt root@217.160.44:/home

Before you boot the server into normal mode, you must unmount the mounted logical volumes or partitions. To do this, use the umount command.

To unmount the mounted logical volumes or partitions, enter the following command:

rescue:/# umount /PATH/Partition /mnt/DIRECTORY

OR

rescue:/# umount /PATH/LOGICAL_VOLUME /mnt/DIRECTORY

In the following example, a partition is unmounted:

rescue:/# umount /dev/sda2 /mnt/sda2