Using Snapshot Driver

This section helps you create a snapshot of the selected disk partition. To create the snapshot using the Snapshot driver, perform the following steps.

Step 1 Create a snapshot device.

Select a disk partition with EXT4 file system (such as /dev/sda2), and execute the following command:

echo -n "create <snapshot device name> /dev/sda2 begin end" > /sys/kernel/cblb/cmd

Where <snapshot device name> refers to the device name that is being created, and /dev/sda2 is the name of the disk partition for which you create a snapshot. The “begin” and “end” parameters mean that you want to create a snapshot for the whole disk partition.

For example, the following command creates the test-sda2 snapshot device for the /dev/sda2 partition:

echo -n "create test-sda2 /dev/sda2 begin end" > /sys/kernel/cblb/cmd

Step 2 Check the creation operation status.

Run the dmesg command to check the creation operation status. If this operation succeded, the output messages should include:

Create snapshot <tst-sda2> for </dev/sda2> 0..end

and information on the sectors and block sizes.

Step 3 Create a catalog for storing temporary files.

The snapshot driver stores temporary data to a catalog you should create. To make a folder for temp files, use the following command:

mkdir <path to catalog>

For example, the following command creates the /tmp/driver catalog:

mkdir /tmp/driver

Step 4 Start the snapshot device.

To start the snapshot device, use the following command:

echo -n “start tst-sda2 /tmp/driver 409600 20” > /sys/kernel/cblb/cmd

where tst-sda2 is the previously used snapshot device name; /tmp/driver refers to a location for storing our temporary files; 409600 is the size of a single temporary file (in blocks), and 20 is a maximum number of files to create.

Step 5 Mount the snapshot device.

Create a catalog for mounting the snapshot device (mount point), such as /tmp/mtst (used as an example):

mkdir /tmp/mtst

Mount the snapshot device (as read only):

sudo mount -o ro,noload /dev/tst-sda2 /tmp/mtst

Step 6 Check whether the snapshot driver works properly

To verify whether the snapshot driver works properly, do the following:

• Navigate to the mount point (such as /tmp/mtst):

cd /tmp/mtst

• View the files list and ensure that it is a copy of the disk partition in question:

ls -lrt

Step 7 Remove the snapshot

To remove snapshot and temporary files, unmount shadow device from previously used mount point(make sure you are not in the mount point directory location path):

sudo umount /tmp/mtst

To remove snapshot and temporary files enter:

echo -n “remove tst-sda2” > /sys/kernel/cblb/cmd

If everything went fine, in dmesg command output you will see something like