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hortitude
Asked: 2012-11-06 13:44:42 +0800 CST

ec2 ami device mapping

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I have large ec2 Ubuntu image and I'm just looking through the devices.

I noticed from the metadata that 

%  curl http://169.254.169.254/latest/meta-data/block-device-mapping/ami
sda1
%  curl http://169.254.169.254/latest/meta-data/block-device-mapping/ephemeral0
sdb

However when I look what is actually mounted there is /dev/xvda1 and /dev/xvdb (and there is no /dev/sd* )

I know that both names look somewhat valid from the AWS documentation, but it looks to me from this like there is a mismatch in the instance metadata and what is actually on the machine.

Why don't they match?

amazon-web-services

2 Answers

  1. If you do an ls -la in /dev you'll see that sda1 links to xvda1

    $ ls -la sd*
lrwxrwxrwx 1 root root 5 Oct 26 15:54 sda1 -> xvda1
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  2. Newer kernels are making these devices (at least under Xen virtualization) appear with names xvdN instead of sdN. Everyone has adapted.

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