| # user(s) | 112 |
| # project(s) | 50 |
| # build(s) | 305 |
| Avg build time | 19.8s |
| Queue len | 0 (0.0) |
| Status | idle |
Erlang on Xen uses 9p-protocol from Plan 9 to mount external filesystems. The same protocol allows mounting of synthetic filesystems exported by Erlang on Xen instances.
All mounting operations require authentication through MUNGE (or MUMBLE) schemes. The authentication requires a synchronisation of secret keys between clients and servers.
Instances get to know the secret keys through a new command-line flag – -secret. For instance, a corresponding line of the domain configuration file may contain:
extra = "-secret 00112233445566 00335577bbdd"
Note that there are two hex hexadecimal numbers that follow -secret.
Two Erlang on Xen nodes that have identical secret keys can mount each other’s filesystems. To access Linux filesystem, we recommend a standard 9p reexporting server – diod.
A -9p command-line flag requests a mounting operation to be performed during the boot process. For instance, the following flag:
extra = "-9p 192.168.0.1 /home /diod"
will establish a 9p connection to a diod server running on 192.168.0.1, and map the /home directory on the server to the /diod directory in the node’s hierarchy.
diod relies of a MUNGE daemon – munged – to verify credentials of incoming clients.
We have created a small utility – mungeling – that retrieves the keys from the munged server and represents them in the format suitable for configuration of Erlang on Xen nodes.
1. You need to download and build munged, diod, and mungeling.
2. Run ‘sudo munged’.
3. Run ‘sudo diod -E’.
4. Run ‘sudo mungeling’. The utility prints ‘-secret xxxxxxxx yyyyyyyy’.
5. Update domain configuration file to include:
extra = "-secret xxxxxxxx yyyyyyyy -9p 192.168.0.1 /home /diod"
6. Launch the instance.
The /home directory of the Linux server is now accessible inside the instance under /diod directory.