# Driver `sync.btrfssnap` **Minimal configlet:** [sync#1] type = btrfssnap subvol = svc1fs:data svc1fs:log **Minimal setup command:** om test/vol/foo set \ --kw="type=btrfssnap" \ --kw="subvol=svc1fs:data svc1fs:log" **Supported keywords:** - blocking_post_provision - blocking_post_unprovision - blocking_pre_provision - blocking_pre_unprovision - comment - disable - encap - keep - log - max_delay - monitor - name - optional - pg_blkio_weight - pg_cpu_burst - pg_cpu_quota - pg_cpu_shares - pg_cpus - pg_mem_high - pg_mem_limit - pg_mem_oom_control - pg_mem_swappiness - pg_mems - pg_pids_max - pg_vmem_limit - post_provision - post_unprovision - pre_provision - pre_unprovision - provision - provision_requires - recursive - schedule - shared - standby - stat_timeout - subset - subvol - tags - type - unprovision - unprovision_requires - update_requires ## Keyword `blocking_post_provision` required: false scopable: true rbac: Triggers require the root grant. **Description:** A command or script to execute after the resource `provision` action. Errors interrupt the action. This trigger is only executed on leaders. ## Keyword `blocking_post_unprovision` required: false scopable: true rbac: Triggers require the root grant. **Description:** A command or script to execute after the resource `unprovision` action. Errors interrupt the action. This trigger is only executed on leaders. ## Keyword `blocking_pre_provision` required: false scopable: true rbac: Triggers require the root grant. **Description:** A command or script to execute before the resource `provision` action. Errors interrupt the action. ## Keyword `blocking_pre_unprovision` required: false scopable: true rbac: Triggers require the root grant. **Description:** A command or script to execute before the resource `unprovision` action. Errors interrupt the action. ## Keyword `comment` required: false scopable: false **Description:** A free form text describing the role of the object, of the node, or of the section it is set in. The keyword is accepted in any section, so the DEFAULT section can document a configuration as a whole, and a resource, pool, heartbeat, array or network section can document itself. The agent does not interpret the value. ## Keyword `disable` required: false scopable: true convert: bool **Description:** A disabled resource will be ignored on `start`, `stop`, `provision` and `unprovision` actions. A disabled resource status is `n/a`. If set in the `DEFAULT` section of an object, the object is disabled and ignores `start`, `stop`, `shutdown`, `provision` and `unprovision` actions. These actions immediately return success. `om disable` sets `DEFAULT.disable=true`. `om enable` sets `DEFAULT.disable=false`. > **Note**: The `enable` and `disable` actions preserve the individual resource `disable` state. ## Keyword `encap` required: false scopable: false convert: bool **Description:** Set to `true` to ignore this resource in the nodes context and consider it in the encapnodes context. The resource is thus handled by agents deployed in the service containers. ## Keyword `keep` required: false scopable: true default: 3 convert: int rbac: A keyword of the btrfssnap driver, which needs the root grant to choose. **Example:** keep=3 **Description:** The maximum number of snapshots to retain. ## Keyword `log` required: false scopable: true default: false convert: bool rbac: A keyword of the btrfssnap driver, which needs the root grant to choose. **Description:** Log the scheduled runs of the resource, the updates the daemon scheduler starts, as a run asked by a user is. The daemon scheduler logs the runs of the jobs it starts only when they ask it, so a scheduled update of a resource with `log = false` leaves no trace in the journal but its status. ## Keyword `max_delay` required: false scopable: false aliases: sync_max_delay convert: duration rbac: A keyword of the btrfssnap driver, which needs the root grant to choose. **Description:** The delay above which the status of the resource reports `warn`. It should be set according to your application service level agreement. The scheduler task interval should be lower than `max_delay`. ## Keyword `monitor` required: false scopable: true convert: bool **Description:** A resource with `monitor=true` will trigger the `monitor_action` (crash or reboot the node, freezestop or switch the service) if: * The resource is `down`. * The instance has `local_expect=started` in its daemon monitor data, which means the daemon considers this instance is and should remain started. * All restart tentatives failed. ## Keyword `name` required: false scopable: true rbac: Requires the root grant. **Example:** name=weekly **Description:** A name included in the snapshot name to avoid retention conflicts between multiple btrfs snapshot resources. A full snapshot name is formatted as `/.snap/Z,`, or `/.snap/Z` without a name. Example: `data/.snap/2026-10-09T10:09:52.000000Z,weekly`. ## Keyword `optional` required: false scopable: true convert: bool **Description:** Action errors on optional resources are logged but do not interrupt the action sequence. The status of optional resources is not included in the instance availability status but is considered in the overall status. The status of task and sync resources is always included in the overall status, regardless of whether they are marked as optional. Resources tagged as `noaction` are considered optional by default. Dump filesystems are a typical use case for optional=true. ## Keyword `pg_blkio_weight` required: false scopable: true **Example:** pg_blkio_weight=50 **Description:** Block IO relative weight. Value: between `10` and `1000`. The kernel default is `100`. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_cpu_burst` required: false scopable: true **Example:** pg_cpu_burst=20% **Description:** The cpu time the group banks under its quota, and spends above it. It is the time the processes of the group may bank while under their `pg_cpu_quota`, and spend above it in a short spike, in the notation of `pg_cpu_quota`: `20%` lets the group run a fifth of a cpu above its quota during a period, out of what it left unused before. It serves a latency-sensitive service capped tightly: a request arriving after an idle spell is served at the speed of the burst, rather than throttled for the rest of the period. Over a longer time the group still uses no more than its quota. It needs `pg_cpu_quota`, and cannot exceed it: the kernel refuses a burst larger than the quota. Only the unified cgroup hierarchy has it. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_cpu_quota` required: false scopable: true **Example:** pg_cpu_quota=50%@all **Description:** The percentage of cpu time the processes of the group may use. Accepted expressions: * `50%` Half of one cpu. * `50%@all` Half of every cpu the node has. * `10%@2` A tenth of two cpus. Unlike `pg_cpu_shares`, which only arbitrates when the node is cpu-bound, a quota caps the group whether or not the node is busy. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_cpu_shares` required: false scopable: true convert: size **Example:** pg_cpu_shares=512 **Description:** The share of cpu the group gets when the node is cpu-bound. The share is relative to the other groups. The actual percentile depends on the shares allowed to the other services. Unset, the kernel default is used, which usually is 1024 shares. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_cpus` required: false scopable: true depends: create_pg=true **Example:** pg_cpus=0-2 **Description:** The cpus the processes of the group may run on. Cpus are specified as list or range : `0,1,2` or `0-2`. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_mem_high` required: false scopable: true convert: size **Example:** pg_mem_high=384m **Description:** The memory past which the kernel throttles the group, in bytes. Past it, the kernel slows the processes of the group down, reclaiming their memory and throttling their allocations. Unlike `pg_mem_limit`, reaching it does not wake the Out-Of-Memory killer: a group above it keeps running, slower, while the kernel reclaims. Set below `pg_mem_limit`, it gives a process growing too much the time to be noticed, or to shrink, before it is killed. It is a soft limit, so it is not what a memory claim counts: the claim counts `pg_mem_limit`. Only the unified cgroup hierarchy has it. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_mem_limit` required: false scopable: true convert: size **Example:** pg_mem_limit=512m **Description:** The memory the processes of the group may use, in bytes. The Out-Of-Memory killer is triggered in case of tresspassing. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_mem_oom_control` required: false scopable: true **Example:** pg_mem_oom_control=1 **Description:** Whether the Out of Memory killer runs for the group: 0 enables it. It is a flag (0 or 1) enabling or disabling the Out of Memory killer for the processes of the group. * If enabled (0), tasks that attempt to consume more memory than they are allowed are immediately killed by the OOM killer. * If disabled (1), tasks are allowed to continue to try allocating memory, stressing the system. The OOM killer is enabled by default in every cgroup using the memory controller. This keyword caps nothing on a node holding the unified cgroup hierarchy, which has no `memory.oom_control`: that file is of the v1 hierarchy. Setting it there is warned about, and ignored. ## Keyword `pg_mem_swappiness` required: false scopable: true **Example:** pg_mem_swappiness=40 **Description:** Set a swappiness percentile value for the process group. This keyword caps nothing on a node holding the unified cgroup hierarchy, which has no `memory.swappiness`: that file is of the v1 hierarchy. Setting it there is warned about, and ignored. ## Keyword `pg_mems` required: false scopable: true **Example:** pg_mems=0-2 **Description:** The memory nodes the processes of the group may allocate from. Memory nodes are specified as list or range : `0,1,2` or `0-2`. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_pids_max` required: false scopable: true **Example:** pg_pids_max=512 **Description:** The most processes and threads the group may run at once. A fork beyond it fails in the process that asked for it, and nothing else of the node is touched: it is what keeps a runaway fork loop from exhausting the process table of the node. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `pg_vmem_limit` required: false scopable: true convert: size **Example:** pg_vmem_limit=1g **Description:** The memory plus swap the processes of the group may use, in bytes. The Out-Of-Memory killer is triggered in case of tresspassing. The specified value must be greater than `pg_mem_limit`. Setting this keyword to `default` puts the capping back where a node that never capped anything leaves it. Removing the keyword does not: what was written stays written, whether om wrote it or something else did. ## Keyword `post_provision` required: false scopable: true rbac: Triggers require the root grant. **Description:** A command or script to execute after the resource `provision` action. Errors do not interrupt the action. This trigger is only executed on leaders. ## Keyword `post_unprovision` required: false scopable: true rbac: Triggers require the root grant. **Description:** A command or script to execute after the resource `unprovision` action. Errors do not interrupt the action. This trigger is only executed on leaders. ## Keyword `pre_provision` required: false scopable: true rbac: Triggers require the root grant. **Description:** A command or script to execute before the resource `provision` action. Errors do not interrupt the action. ## Keyword `pre_unprovision` required: false scopable: true rbac: Triggers require the root grant. **Description:** A command or script to execute before the resource `unprovision` action. Errors do not interrupt the action. ## Keyword `provision` required: false scopable: false default: true convert: bool **Description:** Set to `false` to ignore the `provision` and `unprovision` actions on the resource. > **Warning**: `provision` and `unprovision` use data-destructive operations like formatting. It is recommended to set `provision=false` on long-lived critical objects, to force administrators to remove this setting when they really want to destroy data. ## Keyword `provision_requires` required: false scopable: false **Example:** provision_requires=ip#0 fs#0(down,stdby down) **Description:** A whitespace-separated list of conditions to meet to accept a 'provision' action. A condition is expressed as `(,...)`. If states are omitted, `up,stdby up` is used as the default expected states. ## Keyword `recursive` required: false scopable: true default: false convert: bool rbac: Requires the root grant. **Description:** Also snapshot the writable subvolumes nested in the subvolumes, each in its own `.snap` directory. ## Keyword `schedule` required: false scopable: true rbac: A keyword of the btrfssnap driver, which needs the root grant to choose. **Example:** schedule=00:00-01:00 mon **Description:** Set the task `run` schedule. See `usr/share/doc/opensvc/schedule` for the schedule syntax reference. ## Keyword `shared` required: false scopable: true convert: bool **Description:** If `true`, the resource will be considered shared during provision and unprovision actions. A shared resource driver can implement a different behaviour depending on weither it is run from the leader instance, or not: * When `--leader` is set, the driver creates and configures the system objects. For example the disk.disk driver allocates a SAN disk and discover its block devices. * When `--leader` is not set, the driver does not redo the actions already done by the leader, but may do some. For example, the disk.disk driver skips the SAN disk allocation, but discovers the block devices. The daemon takes care of setting the `--leader` flags on the commands it submits during deploy, purge, provision and unprovision orchestrations. > **Warning**: If admins want to submit `--local` provision or unprovision commands themselves, they have to set the `--leader` flag correctly. Flex objects usually don't use shared resources. But if they do, only the flex primary gets `--leader` commands. > **Warning**: All resources depending on a shared resource must also be flagged as shared. ## Keyword `standby` required: false scopable: true convert: bool **Description:** If `true`, always start the resource, even on non-started instances. The daemon is responsible for starting standby resources. A resource can be set standby on a subset of nodes using keyword scoping. A typical use-case is a synchronized filesystem on non-shared disks. The remote filesystem must be mounted to not overflow the underlying filesystem. > **Warning**: In most situation, don't set shared resources standby, a non-clustered fs on shared disks for example. ## Keyword `stat_timeout` required: false scopable: true convert: duration **Description:** The fs resources status evaluation includes a stat syscall test. This keyword defines the maximum wait time for those stat calls to respond. When expired, the resource status is degraded is to warn, which can trigger a monitor action (reboot or crash the node) if the resource is monitored. ## Keyword `subset` required: false scopable: true **Description:** The name of the subset this resource is assigned to. Resources of a same driver group and a same subset are ordered and acted upon together, and are configured as a whole in a `[subset#:]` section, or in a less precise `[subset#]` one. That section accepts `parallel`, to act on the members concurrently rather than one after the other, and the `pg_*` keywords, to place the members in their own process group. ## Keyword `subvol` required: true scopable: true convert: list rbac: Requires the root grant. **Example:** subvol=svc1fs:data svc1fs:log **Description:** A whitespace separated list of `