projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 3efd9988 FG |
1 | .. _ceph-volume-systemd: |
| 2 | ||
| 3 | systemd | |
| 4 | ======= | |
| 5 | As part of the activation process (either with :ref:`ceph-volume-lvm-activate` | |
| 6 | or :ref:`ceph-volume-simple-activate`), systemd units will get enabled that | |
| 7 | will use the OSD id and uuid as part of their name. These units will be run | |
| 8 | when the system boots, and will proceed to activate their corresponding | |
| 9 | volumes via their sub-command implementation. | |
| 10 | ||
| 11 | The API for activation is a bit loose, it only requires two parts: the | |
| 12 | subcommand to use and any extra meta information separated by a dash. This | |
| 13 | convention makes the units look like:: | |
| 14 | ||
| 15 | ceph-volume@{command}-{extra metadata} | |
| 16 | ||
| 17 | The *extra metadata* can be anything needed that the subcommand implementing | |
| 18 | the processing might need. In the case of :ref:`ceph-volume-lvm` and | |
| 19 | :ref:`ceph-volume-simple`, both look to consume the :term:`OSD id` and :term:`OSD uuid`, | |
| 20 | but this is not a hard requirement, it is just how the sub-commands are | |
| 21 | implemented. | |
| 22 | ||
| 23 | Both the command and extra metadata gets persisted by systemd as part of the | |
| 24 | *"instance name"* of the unit. For example an OSD with an ID of 0, for the | |
| 25 | ``lvm`` sub-command would look like:: | |
| 26 | ||
| 27 | systemctl enable ceph-volume@lvm-0-0A3E1ED2-DA8A-4F0E-AA95-61DEC71768D6 | |
| 28 | ||
| 29 | The enabled unit is a :term:`systemd oneshot` service, meant to start at boot | |
| 30 | after the local filesystem is ready to be used. | |
| 31 | ||
| 32 | ||
| 33 | Failure and Retries | |
| 34 | ------------------- | |
| 35 | It is common to have failures when a system is coming up online. The devices | |
| 36 | are sometimes not fully available and this unpredictable behavior may cause an | |
| 37 | OSD to not be ready to be used. | |
| 38 | ||
| 39 | There are two configurable environment variables used to set the retry | |
| 40 | behavior: | |
| 41 | ||
| 42 | * ``CEPH_VOLUME_SYSTEMD_TRIES``: Defaults to 30 | |
| 43 | * ``CEPH_VOLUME_SYSTEMD_INTERVAL``: Defaults to 5 | |
| 44 | ||
| 45 | The *"tries"* is a number that sets the maximum amount of times the unit will | |
| 46 | attempt to activate an OSD before giving up. | |
| 47 | ||
| 48 | The *"interval"* is a value in seconds that determines the waiting time before | |
| 49 | initiating another try at activating the OSD. |