Issue
I had some unknown issue with my old EC2 instance so that I can't ssh into it anymore. Therefore I'm attempting to create a new EBS volume from a snapshot of the old volume and mount it into the new instance. Here is exactly what I did:
- Created a new volume from snapshot of the old one.
- Created a new EC2 instance and attached the volume to it as
/dev/xvdf(or/dev/sdf) 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
I know I should specify the filesytem as ext4 but the volume contains a lot of important data, so I cannot afford to format it with $ sudo mkfs -t ext4 /dev/xvdf. If I try 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
And 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
By the way, the 'mounting read-only' message also worries me but I haven't look into it yet since I can't mount the volume at all.
Thanks in advance!
Solution
The One Liner
🥇 Mount the partition (if disk is partitioned):
sudo mount /dev/xvdf1 /vol -t ext4
Mount the disk (if not partitioned):
sudo mount /dev/xvdf /vol -t ext4
where:
/dev/xvdfis changed to the EBS Volume device being mounted/volis changed to the folder you want to mount to.ext4is the filesystem type of the volume being mounted
Common Mistakes How To:
✳️ Attached Devices List
Check your mount command for the correct EBS Volume device name and filesystem type. The following will list them all:
sudo lsblk --output NAME,TYPE,SIZE,FSTYPE,MOUNTPOINT,UUID,LABEL
If your EBS Volume displays with an attached partition, mount the partition; not the disk.
✳️ If your volume isn't listed
If it doesn't show, you didn't Attach your EBS Volume in AWS web-console
✳️ 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 add the volume to the server's /etc/fstab file.
🔥 Caution:🔥
If you corrupt the /etc/fstab file, it will make your system unbootable. Read AWS's short article so you know to check that you did it correctly.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-using-volumes.html#ebs-mount-after-reboot
First:
With the lsblk command above, find your volume's UUID & FSTYPE.
Second:
Keep a copy of your original fstab file.
sudo cp /etc/fstab /etc/fstab.original
Third:
Add a line for the volume in sudo nano /etc/fstab.
The fields of fstab are 'tab-separated' and each line has the following fields:
<UUID> <MOUNTPOINT> <FSTYPE> defaults,discard,nofail 0 0
Here's an example to help you, my own fstab reads as follows:
LABEL=cloudimg-rootfs / ext4 defaults,discard,nofail 0 0
UUID=e4a4b1df-cf4a-469b-af45-89beceea5df7 /var/www-data ext4 defaults,discard,nofail 0 0
That's it, you're done. Check for errors in your work by running:
sudo mount --all --verbose
You will see something like this if things are 👍:
/ : ignored
/var/www-data : already mounted
Answered By - FactoryAidan Answer Checked By - Pedro (WPSolving Volunteer)
