In Linux, you can configure the fstab file to have the file systems of data disks automatically mounted on the startup of an Elastic Compute Service (ECS) instance. If the fstab file is inappropriately configured and the attach sequence of your disks is changed, the ECS instance may not run normally after it is restarted. This topic describes how to configure universally unique identifiers (UUIDs) in the fstab file to automatically mount the system files of data disks. This can handle the preceding restart exception.

Prerequisites

The disks attached to the instance are partitioned and formatted. For more information, see Partition and format a data disk on a Linux instance.

Background information

fstab allows you to identify a file system by using a disk partition name such as/dev/vdb1 or by using a UUID. The two methods differ in the following aspects:
  • If disk partition names are used to identify file systems in the fstab file, the disk partitions may not be mounted to the original mount points if the attach sequence of the disks is changed. In this case, applications that run on your ECS instance may be affected.
  • If UUIDs are used to identify file systems in the fstab file, the disk partitions can still be mounted to the original mount points if the attach sequence of the disks is changed. Therefore, we recommend that you use UUIDs to identify file systems.

Procedure

  1. Connect to the ECS instance.

    For information about how to connect to an ECS instance, see Connect to a Linux instance by using a password or key.

  2. Run the following command to view information of the disks attached to the instance:
     fdisk -lu
    A command output similar to the following one is returned. Query the disks
  3. Run the following command to query the UUIDs of the disks:
    blkid
    A command output similar to the following one is returned. Query the UUIDs
  4. Run the following commands to create the mount points for the data disks:
    • Create the /test01 mount point for /dev/vdb1:
      mkdir /test01
    • Create the /test02 mount point for /dev/vdc1:
      mkdir /test02
  5. Add the mount information to the fstab file.
    1. Run the following command to edit the fstab file:
      vi /etc/fstab
    2. Press the I key to enter the edit mode.
    3. Add the following mount information:
      UUID=59f23670-94c1-42d1-8bb0-209d7854****   /test01     ext4    defaults     0   0
      UUID=88619b1a-d971-41c2-91d0-3a440fc0****   /test02     xfs     defaults     0   0
      A command output similar to the following one is returned. Description of the fstab file
      No. Section Description
      <file system> The file systems to be mounted to the partitions.

      We recommend that you use the UUIDs of the file systems. You can run the blkid command to query the UUIDs of the file systems in the partitions.

      <dir> The mount points of the file systems.

      You can create mount points. In this topic, the /test01 and /test02 mount points are created.

      <type> The types of file systems to be mounted to the partitions.

      You can run the blkid command to query the types of the file systems.

      <options> The parameters used for mounting. Typically, the defaults parameter is used. If you want to use multiple parameters, separate them with commas (,). Example: defaults,noatime.

      For more information about the <options> parameters, see fstab.

      <dump> Indicates whether the dump tool backs up the file systems.
      • 0: The dump tool does not back up the file systems.
      • 1: The dump tool backs up the file systems.

      Typically, the dump tool is not used. In this case, this parameter is set to 0.

      <pass> The priority in which fsck checks the file systems.
      • 0: The file systems are not checked.
      • 1: The file system corresponding to root directory (/) is checked.
      • 2: All file systems except the one corresponding to root directory (/) are checked.

      Typically, this parameter is set to 0.

    4. Press the Esc key to exit the edit mode after you complete the preceding configurations.
    5. Enter :wq and press the Enter key to save and exit the file.
  6. Run the following command to view the fstab file:
    cat /etc/fstab
    A command output similar to the following one is returned. Query fstab
  7. Run the following command to mount the file systems of the data disk partitions.
    • To mount /dev/vdb1, run the following command:
      mount /dev/vdb1 /test01
    • To mount /dev/vdc1, run the following command:
      mount /dev/vdc1 /test02
  8. Run the following command to check whether the file systems of the data disk partitions are mounted:
    df -h

    A command output similar to the following one is returned:

    Query result

After the fstab file is configured, the system attaches the data disks after you restart the ECS instance.

FAQ

What do I do if system startup exceptions occur due to the configuration errors of the /etc/fstab file on Linux instances?