Using the Ceph metavariables
Metavariables simplify Ceph storage cluster configuration dramatically. When a metavariable is set in a configuration value, Ceph expands the metavariable into a concrete value.
Metavariables are powerful when used within the [global],
[osd], [mon], or [client] sections of the Ceph
configuration file. However, you can also use them with the administration socket. Ceph
metavariables are similar to Bash shell expansion.
Ceph supports the following metavariables, as listed in Table 1:
| Metavariable | Description | Example | Default |
|---|---|---|---|
$cluster |
Expands to the Ceph storage cluster name. Useful when running multiple Ceph storage clusters on the same hardware. | /etc/ceph/$cluster.keyring |
ceph |
$type |
Expands to one of osd or mon, depending on the type of
instant daemon. |
/var/lib/ceph/$type |
None. |
$id |
Expands to the daemon identifier. For osd.0, this would be
0. |
/var/lib/ceph/$type/$cluster-$id |
None. |
$host |
Expands to the host name of the instant daemon. | N/A | None. |
$name |
Expands to $type.$id. |
/var/run/ceph/$cluster-$name.asok |
None. |