lxc-attach failed to enter the namespace - EC2 Instances

Question

For some reason I cannot enter a docker container using Lxc-attach only on EC2 instances. This works on my local machine and on Digital Ocean (KVM) droplets but not on Amazon EC2 xen-paravirtualized Ubuntu12.04 instance. Here are the steps/errors:

root@ip-172-31-46-202:~/scalar/project/docker# lxc-ls
4074ebf985cfe09b2880a9eabbc7ad3e59283f425f64cfaa72f59f1f23661d18

root@ip-172-31-46-202:~/scalar/project/docker# lxc-attach -n 4074ebf985cfe09b2880a9eabbc7ad3e59283f425f64cfaa72f59f1f23661d18
lxc-attach: No such file or directory - failed to open '/proc/19731/ns/pid'
lxc-attach: failed to enter the namespace

Does anyone know if there is a way to resolve this issue? Here are my docker version details:

Client version: 0.7.6
Go version (client): go1.2
Git commit (client): bc3b2ec
Server version: 0.7.6
Git commit (server): bc3b2ec
Go version (server): go1.2
Last stable version: 0.7.6

Also:

lxc version: 0.7.5

Answer 1

What is your kernel version?

lxc-attach requires features that are not present in the native 12.04 kernel (3.5). You need at least 3.8 which IIRC is available in the backport.

Answer 2

As Creac suggested, the kernel was not of a high enough version. (and if I try re-deploying an AWS ubuntu image it still uses kernel 3.2)

To fix this issue, I ran the following command to get 3.8:

sudo apt-get install linux-image-generic-lts-raring linux-headers-generic-lts-raring

or you can run the following command to get 3.5

sudo apt-get install linux-image-generic-lts-quantal linux-headers-generic-lts-quantal

Please note that these commands are Ubuntu specific (as per the question) and will install the "generic" kernel rather than the "virtual" kernel, but should work. [source]

Note that I tried to update Creac's original answer with this additional information but the edit was rejected so I felt the need to create a new answer for others to use if they want.

source of where I found the commands