# man > dmeventd(8)

---
type: CommandReference
command: dmeventd
mode: man
section: 8
source: man-pages
---

## Quick Reference

- `dmeventd` — Start the event monitoring daemon
- `dmeventd -f` — Run in foreground (do not fork)
- `dmeventd -d` — Debug output to syslog (repeat up to 3 times)
- `dmeventd -R` — Replace a running daemon instance
- `dmeventd -l` — Log to stdout/stderr (requires `-f`)
- `dmeventd -V` — Show version
- `dmeventd -h` — Show help
- `dmeventd -?` — Show help on stderr

## Name

**dmeventd** — Device-mapper event daemon

## Synopsis

`dmeventd` [`-d` [`-d` [`-d`]]] [`-f`] [`-h`] [`-l`] [`-R`] [`-V`] [`-?`]

## Options

- `-d` — Increase debug verbosity to syslog. Repeat 1–3 times (`-d`, `-dd`, `-ddd`).
- `-f` — Run in foreground (do not fork).
- `-h` — Show help.
- `-l` — Log through stdout/stderr instead of syslog (only with `-f`).
- `-R` — Replace a running instance (v2.02.77+). New daemon obtains monitored devices from the old one.
- `-V` — Show version.
- `-?` — Show help on stderr.

## LVM Plugins

### Mirror

Attempts to handle device failure automatically. See [lvm.conf(5)](https://www.chedong.com/phpMan.php/man/lvm.conf/5/markdown).

### Raid

Attempts to handle device failure automatically. See [lvm.conf(5)](https://www.chedong.com/phpMan.php/man/lvm.conf/5/markdown).

### Snapshot

Monitors snapshot fullness. Emits warnings to syslog at 80%, 85%, 90%, 95% full. When snapshot runs out of space, it becomes invalid and is unmounted if possible. See [lvm.conf(5)](https://www.chedong.com/phpMan.php/man/lvm.conf/5/markdown).

### Thin

Monitors thin pool data and metadata fullness. Warns at 80%, 85%, 90%, 95% full. Above 50% full, calls `lvm lvextend --use-policies` (default) every 5% increase, or an external command configured in `dmeventd/thin_command`. Retries with increasing delay up to 42 minutes on failure. External command can use `fstrim`, `lvextend`, etc. Executed with `LVM_RUN_BY_DMEVENTD=1` to prevent recursion. Environment variables `DMEVENTD_THIN_POOL_DATA` and `DMEVENTD_THIN_POOL_METADATA` provide usage ratios. See [lvm.conf(5)](https://www.chedong.com/phpMan.php/man/lvm.conf/5/markdown).

### Vdo

Monitors VDO pool data fullness. Warns at 80%, 85%, 90%, 95% full. Above 50% full, calls `lvm lvextend --use-policies` (default) every 5%, or external command configured in `dmeventd/vdo_command`. Retries with increasing delay up to 42 minutes. External command can use `fstrim`, `lvextend`. Executed with `LVM_RUN_BY_DMEVENTD=1`. Environment variable `DMEVENTD_VDO_POOL` provides usage ratio. See [lvm.conf(5)](https://www.chedong.com/phpMan.php/man/lvm.conf/5/markdown).

## Environment Variables

- `DMEVENTD_THIN_POOL_DATA` — Set by thin plugin; actual usage of thin pool data volume. Not set during error events.
- `DMEVENTD_THIN_POOL_METADATA` — Set by thin plugin; actual usage of thin pool metadata volume. Not set during error events.
- `DMEVENTD_VDO_POOL` — Set by vdo plugin; actual usage of VDO pool data volume. Not set during error events.
- `LVM_RUN_BY_DMEVENTD` — Set by thin and vdo plugins to prevent recursion in executed lvm2 commands.

## See Also

[lvm(8)](https://www.chedong.com/phpMan.php/man/lvm/8/markdown), [lvm.conf(5)](https://www.chedong.com/phpMan.php/man/lvm.conf/5/markdown), [fstrim(8)](https://www.chedong.com/phpMan.php/man/fstrim/8/markdown), [lvs(8)](https://www.chedong.com/phpMan.php/man/lvs/8/markdown)