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Failed to Start the VM Due to Incorrect VM Image File Data

Publication Date:  2014-07-15 Views:  9 Downloads:  0
Issue Description
A user intended to use a VM image in .raw format. The .raw format, however, is not supported by the SingleCloud GPI. The SingleCloud GUIP supports .gz, :tar.gz, :img, and :tar. The user then converted the .raw image to a .tar file by running the tar command, so that the SingleCloud could recognize it. The VM deployed by using this image file could not be restarted.
Alarm Information
none
Handling Process
Rename the original.raw image file to an .img name, and then import it to the mirror server, so that the SingleCloud can recognize the file.
Root Cause
1. Start the VM, and attempt to log in through the VNC. The following message is displayed: Boot failed: not a bootable disk.
The possible causes are as follows:
a. The image is damaged.
b. The image data is incorrect, and cannot guide through OS boot based on the disk information.
2. Use the hexdump tool to check the 1024 bytes of the VM image file header. It is found that the first 512 bytes are tar command-related information, as shown in Figure 1. (0x00000200 = 512 bytes).
Figure 1 First 512 bytes

The later 512 bytes are the OS boot data, as shown in Figure 2.
Figure 2 OS boot data

3. The user mistakenly used the tar command to compress the image file, causing incorrect image file header data. For a .raw VM image, the first 512 bytes must be OS boot information so that the OS can start properly.
Suggestions
1. If the VM cannot be started or it restarts repeatedly, the VM image file is faulty, causing OS boot failure.
2. Use the hexdump command to view the hexadecimal data of the disk and determine whether the image is damaged.
3. Different from the Windows OS, the Linux OS uses only the file data. You can change the file name extension for the SingleCloud to recognize the file directory.

END