Gabriel Rebello Gabriel Rebello - 4 months ago 228x
Linux Question

Attaching and mounting existing EBS volume to EC2 instance filesystem issue

I had some unknown issue with my old EC2 instance so that I can't ssh into it anymore. Therefore I created a new EBS volume from a snapshot of the old volume and tried to attach and mount it to the new instance. Here is what I did:

  1. Created a new volume from snapshot of the old one.

  2. Created a new EC2 instance and attached the volume to it as

  3. SSHed into the instance and attempted to mount the old volume with:

    $ sudo mkdir -m 000 /vol
    $ sudo mount /dev/xvdf /vol

And the output was:

mount: block device /dev/xvdf is write-protected, mounting read-only
mount: you must specify the filesystem type

Now, I know I should specify the filesytem as
but since the volume contains a lot of important data, I cannot format it through
$ sudo mkfs -t ext4 /dev/xvdf
. Still, I know of no other way of preserving the data and specifying the filesystem at the same time. I've searched a lot about it and I'm currently at a loss.

By the way, the mounting as 'read-only' also worries me but I haven't look into it yet since I can't mount the volume at all.

Thanks in advance!


When I do
sudo mount /dev/xvdf /vol -t ext4
(no formatting) I get:

mount: wrong fs type, bad option, bad superblock on /dev/xvdf,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

dmesg | tail
gives me:

[ 1433.217915] EXT4-fs (xvdf): VFS: Can't find ext4 filesystem
[ 1433.222107] FAT-fs (xvdf): bogus number of reserved sectors
[ 1433.226127] FAT-fs (xvdf): Can't find a valid FAT filesystem
[ 1433.260752] EXT4-fs (xvdf): VFS: Can't find ext4 filesystem
[ 1433.265563] EXT4-fs (xvdf): VFS: Can't find ext4 filesystem
[ 1433.270477] EXT4-fs (xvdf): VFS: Can't find ext4 filesystem
[ 1433.274549] FAT-fs (xvdf): bogus number of reserved sectors
[ 1433.277632] FAT-fs (xvdf): Can't find a valid FAT filesystem
[ 1433.306549] ISOFS: Unable to identify CD-ROM format.
[ 2373.694570] EXT4-fs (xvdf): VFS: Can't find ext4 filesystem


The One Liner

Use this command to mount it if your filesystem type is ext4:

sudo mount /dev/xvdf /vol -t ext4


  • /dev/xvdf is changed to the EBS Volume device being mounted
  • /vol is changed to the folder you want to mount to.
  • ext4 is the filesystem type of the volume being mounted

The mount command is non-destructive so it is not to be confused with accidentally reformatting your already formatted EBS Volume.

Common Mistakes How To:

Attached Devices List

Check your mount command for EBS Volume device names and filesystem types that are actually attached to your EC2 Instance. This command will list them all:

sudo blkid -o list

If it doesn't show, you need a reboot or didn't Attach your EBS volume in AWS web-console. sudo fdisk -l is a similar list command to verify you aren't crazy.

Auto Remounting on Reboot

These devices become unmounted again if the EC2 Instance ever reboots.

A way to make them mount again upon startup is to edit the server file listed below and insert just the single mount command that you originally used.


(Place your change above exit 0, the last line in this file.)