I've not been able to use a 64-bit linux server as a backup repository - the agent used by veeam is 32-bit (I "captured" it before it was deleted and checked), and there is no 32-bit support on this server. Most major linux distros in default install have 32-bit support, so they are able to run the agent.
I contacted support, which told me
You are absolutely right, the only version of our Linux agent is 32-bit version.
However, the FAQ seems to say otherwise, which leaves me confused. I assume support is correct and the FAQ is wrong or misleading, it would be nice to see it clarified.Unfortunately we can't provide you with the 64-bit Linux agent at the moment. You are the first customer that have asked for such a feature, and I will be glad to create a feature request for you.
Is there really no demand for actual 64-bit linux support?
From the FAQ:
Q: Do 7.0 backup proxies and backup repositories still support both 32-bit and 64-bit OS?
A: Yes, meaning you can keep your backup proxies and backup repositories intact. However, we recommend using 64-bit servers for backup repositories, as this provides for supporting larger backup sizes.
Q: What do you support as a backup repository?
A: The following repositories are supported:
<snip>
• Any storage directly attached to, or mounted on a Linux server (x86 and x64 of all major distributions are supported, must have SSH and Perl installed). The storage can be local disks, directly attached disk based storage (such as USB hard drive), NFS share, or iSCSI/FC SAN LUN in case the server is connected into the SAN fabric.