Making an Amazon EBS Volume Available for Use
After you attach an Amazon EBS volume to your instance, it is exposed as a block device. You can format the volume with any file system and then mount it. After you make the EBS volume available for use, you can access it in the same ways that you access any other volume. Any data written to this file system is written to the EBS volume and is transparent to applications using the device.
Note that you can take snapshots of your EBS volume for backup purposes or to use as a baseline when you create another volume. For more information, see Amazon EBS Snapshots.
Making the Volume Available on Linux
Use the following procedure to make the volume available. Note that you can get directions for volumes on a Windows instance from Making the Volume Available on Windows in the Amazon EC2 User Guide for Windows Instances.
To make an EBS volume available for use on Linux
Connect to your instance using SSH. For more information, see Step 2: Connect to Your Instance.
Depending on the block device driver of the kernel, the device might be attached with a different name than what you specify. For example, if you specify a device name of
/dev/sdh, your device might be renamed
/dev/hdhby the kernel; in most cases, the trailing letter remains the same. In some versions of Red Hat Enterprise Linux (and its variants, such as CentOS), even the trailing letter might also change (where
/dev/xvde). In these cases, each device name trailing letter is incremented the same number of times. For example,
/dev/xvdg. Amazon Linux AMIs create a symbolic link with the name you specify at launch that points to the renamed device path, but other AMIs might behave differently.
Use the lsblk command to view your available disk devices and their mount points (if applicable) to help you determine the correct device name to use.
The output of lsblk removes theCopy
lsblkNAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT xvdf 202:80 0 100G 0 disk xvda1 202:1 0 8G 0 disk /
/dev/prefix from full device paths. In this example,
/dev/xvda1is mounted as the root device (note the
MOUNTPOINTis listed as
/, the root of the Linux file system hierarchy), and
/dev/xvdfis attached, but it has not been mounted yet.
Determine whether you need to create a file system on the volume. New volumes are raw block devices, and you need to create a file system on them before you can mount and use them. Volumes that have been restored from snapshots likely have a file system on them already; if you create a new file system on top of an existing file system, the operation overwrites your data. Use the sudo file -s
devicecommand to list special information, such as file system type.Copy
sudo file -s /dev/xvdf/dev/xvdf: data
If the output of the previous command shows simply
datafor the device, then there is no file system on the device and you need to create one. You can go on to Step 4. If you run this command on a device that contains a file system, then your output will be different.Copy
sudo file -s /dev/xvda1/dev/xvda1: Linux rev 1.0 ext4 filesystem data, UUID=1701d228-e1bd-4094-a14c-8c64d6819362 (needs journal recovery) (extents) (large files) (huge files)
In the previous example, the device contains
Linux rev 1.0 ext4 filesystem data, so this volume does not need a file system created (you can skip Step 4 if your output shows file system data).
(Conditional) Use the following command to create an ext4 file system on the volume. Substitute the device name (such as
device_name. Depending on the requirements of your application or the limitations of your operating system, you can choose a different file system type, such as ext3 or XFS.
This step assumes that you're mounting an empty volume. If you're mounting a volume that already has data on it (for example, a volume that was restored from a snapshot), don't use mkfs before mounting the volume (skip to the next step instead). Otherwise, you'll format the volume and delete the existing data.Copy
sudo mkfs -t ext4
Use the following command to create a mount point directory for the volume. The mount point is where the volume is located in the file system tree and where you read and write files to after you mount the volume. Substitute a location for
mount_point, such as
Use the following command to mount the volume at the location you just created.Copy
(Optional) To mount this EBS volume on every system reboot, add an entry for the device to the
Create a backup of your
/etc/fstabfile that you can use if you accidentally destroy or delete this file while you are editing it.Copy
sudo cp /etc/fstab /etc/fstab.orig
/etc/fstabfile using any text editor, such as nano or vim.
You need to open the file as
rootor by using the sudo command.
Add a new line to the end of the file for your volume using the following format:
The last three fields on this line are the file system mount options, the dump frequency of the file system, and the order of file system checks done at boot time. If you don't know what these values should be, then use the values in the following example for them (Copy
defaults,nofail 0 2). For more information on
/etc/fstabentries, see the fstab manual page (by entering man fstab on the command line).
You can use the system's current device name (
/dev/xvda1, etc.) in
/etc/fstab, but we recommend using the device's 128-bit universally unique identifier (UUID) instead. System-declared block-device names may change under a variety of circumstances, but the UUID is assigned to a volume partition when it is formatted and persists throughout the partition's service life. By using the UUID, you reduce the chances of the block-device mapping in
/etc/fstableaving the system unbootable after a hardware reconfiguration.
To find the UUID of a device, first display the available devices:Copy
This yields a list such as the following:Copy
Filesystem 1K-blocks Used Available Use% Mounted on /dev/xvda1 8123812 1876888 6146676 24% / devtmpfs 500712 56 500656 1% /dev tmpfs 509724 0 509724 0% /dev/shm
Next, continuing this example, examine the output of either of two commands to find the UUID of
sudo file -s
ls -al /dev/disk/by-uuid/
Assuming that you find
/dev/xvda1to have UUID
de9a1ccd-a2dd-44f1-8be8-0123456abcdef, you would add the following entry to
/etc/fstabto mount an ext4 file system at mount point
UUID=de9a1ccd-a2dd-44f1-8be8-0123456abcdef /data ext4 defaults,nofail 0 2
If you ever intend to boot your instance without this volume attached (for example, so this volume could move back and forth between different instances), you should add the
nofailmount option that allows the instance to boot even if there are errors in mounting the volume. Debian derivatives, including Ubuntu versions earlier than 16.04, must also add the
After you've added the new entry to
/etc/fstab, you need to check that your entry works. Run the sudo mount -a command to mount all file systems in
sudo mount -a
If the previous command does not produce an error, then your
/etc/fstabfile is OK and your file system will mount automatically at the next boot. If the command does produce any errors, examine the errors and try to correct your
Errors in the
/etc/fstabfile can render a system unbootable. Do not shut down a system that has errors in the
(Optional) If you are unsure how to correct
/etc/fstaberrors, you can always restore your backup
/etc/fstabfile with the following command.Copy
sudo mv /etc/fstab.orig /etc/fstab
Review the file permissions of your new volume mount to make sure that your users and applications can write to the volume. For more information about file permissions, see File security at The Linux Documentation Project.