Re: Character limit for rbd block device

[Josh Durgin <josh.durgin@inktank.com>]

On 11/26/2012 04:10 PM, brady wrote:
> Hello,
>      I have a general question. Is there a specific character limit for
> rbd block devices? In attempting to map a block device with a name that
> is 36 characters or more, I am getting the following error:
>
> rbd map (36+ character name) --user admin --secret /etc/ceph/keyring.key
> add failed: (2) No such file or directory
>
>      When using the same command to map a device with 35 characters or
> less, the device is mapped as expected. Any insight into this issue
> would be greatly appreciated.
>
> -Brady

Which kernel version are you using?

A year ago there was a 40-char limit on objects names in the kernel's
libceph module, hence the failure at 36 char rbd image names (36 char
name + ".rbd" is the format 1 header object name).

This was extended to a 96-char limit in linux 3.2. There's no real limit
in userspace still (http://tracker.newdream.net/issues/1701).

Josh