{
    "mode": "man",
    "parameter": "dmeventd",
    "section": "8",
    "url": "https://www.chedong.com/phpMan.php/man/dmeventd/8/json",
    "generated": "2026-06-15T18:52:32Z",
    "synopsis": "dmeventd [-d [-d [-d]]] [-f] [-h] [-l] [-R] [-V] [-?]",
    "sections": {
        "NAME": {
            "content": "dmeventd — Device-mapper event daemon\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "dmeventd [-d [-d [-d]]] [-f] [-h] [-l] [-R] [-V] [-?]\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "dmeventd  is the event monitoring daemon for device-mapper devices.  Library plugins can reg‐\nister and carry out actions triggered when particular events occur.\n",
            "subsections": []
        },
        "OPTIONS": {
            "content": "",
            "subsections": [
                {
                    "name": "-d",
                    "content": "Repeat from 1 to 3 times ( -d, -dd, -ddd ) to increase the detail  of  debug  messages\nsent to syslog.  Each extra d adds more debugging information.\n",
                    "flag": "-d"
                },
                {
                    "name": "-f",
                    "content": "Don't fork, run in the foreground.\n",
                    "flag": "-f"
                },
                {
                    "name": "-h",
                    "content": "Show help information.\n",
                    "flag": "-h"
                },
                {
                    "name": "-l",
                    "content": "Log  through  stdout and stderr instead of syslog.  This option works only with option\n-f, otherwise it is ignored.\n\n-?\nShow help information on stderr.\n",
                    "flag": "-l"
                },
                {
                    "name": "-R",
                    "content": "Replace a running dmeventd instance. The running dmeventd must be version  2.02.77  or\nnewer.  The  new dmeventd instance will obtain a list of devices and events to monitor\nfrom the currently running daemon.\n",
                    "flag": "-R"
                },
                {
                    "name": "-V",
                    "content": "Show version of dmeventd.\n",
                    "flag": "-V"
                }
            ]
        },
        "LVM PLUGINS": {
            "content": "",
            "subsections": [
                {
                    "name": "Mirror",
                    "content": "Attempts to handle device failure automatically. See lvm.conf(5).\n"
                },
                {
                    "name": "Raid",
                    "content": "Attempts to handle device failure automatically. See lvm.conf(5).\n"
                },
                {
                    "name": "Snapshot",
                    "content": "Monitors how full a snapshot is becoming and emits a warning to syslog when it exceeds\n80%  full.   The  warning is repeated when 85%, 90% and 95% of the snapshot is filled.\nSee lvm.conf(5).  Snapshot which runs out  of  space  gets  invalid  and  when  it  is\nmounted, it gets umounted if possible.\n"
                },
                {
                    "name": "Thin",
                    "content": "Monitors  how  full  a  thin pool data and metadata is becoming and emits a warning to\nsyslog when it exceeds 80% full.  The warning is repeated when more then 85%, 90%  and\n95%  of  the  thin  pool  is filled. See lvm.conf(5).  When a thin pool fills over 50%\n(data or metadata) thin plugin calls configured dmeventd/thincommand  with  every  5%\nincrease.   With  default setting it calls internal lvm lvextend --use-policies to re‐\nsize  thin  pool  when  it's  been   filled   above   configured   threshold   activa‐\ntion/thinpoolautoextendthreshold.   If the command fails, dmeventd thin plugin will\nkeep retrying execution with increasing time delay between retries  upto  42  minutes.\nUser  may  also configure external command to support more advanced maintenance opera‐\ntions of a thin pool.  Such external command can e.g. remove some unneeded  snapshots,\nuse  fstrim(8)  to  free  recover  space  in  a  thin  pool, but also can use lvextend\n--use-policies if other actions have not released enough space.  Command  is  executed\nwith environmental variable LVMRUNBYDMEVENTD=1 so any lvm2 command executed in this\nenvironment will not try to interact with dmeventd.  To see the  fullness  of  a  thin\npool  command  may check these two environmental variables DMEVENTDTHINPOOLDATA and\nDMEVENTDTHINPOOLMETADATA.  Command can also read status with tools like lvs(8).\n\n"
                },
                {
                    "name": "Vdo",
                    "content": "Monitors how full a VDO pool data is becoming and emits a warning to  syslog  when  it\nexceeds  80% full.  The warning is repeated when more then 85%, 90% and 95% of the VDO\npool is filled. See lvm.conf(5).  When a VDO pool fills over 50% vdo plugin calls con‐\nfigured  dmeventd/vdocommand  with  every 5% increase.  With default setting it calls\ninternal lvm lvextend --use-policies to resize VDO pool when it's  been  filled  above\nthe  configured  threshold  activation/vdopoolautoextendthreshold.   If the command\nfails, dmeventd vdo plugin will keep retrying execution with increasing time delay be‐\ntween  retries  upto  42 minutes.  User may also configure external command to support\nmore advanced maintenance operations of a VDO pool.  Such external  command  can  e.g.\nremove some unneeded space with fstrim(8), but also can use lvextend --use-policies if\nother actions have not released enough space.  Command is executed with  environmental\nvariable  LVMRUNBYDMEVENTD=1  so any lvm2 command executed in this environment will\nnot try to interact with dmeventd.  To see the fullness of  a  VDO  pool  command  may\ncheck  this  environmental  variable  DMEVENTDVDOPOOL.  Command can also read status\nwith tools like lvs(8).\n"
                }
            ]
        },
        "ENVIRONMENT VARIABLES": {
            "content": "DMEVENTDTHINPOOLDATA\nVariable is set by thin plugin and is available to executed program. Value present ac‐\ntual  usage  of  thin  pool  data volume. Variable is not set when error event is pro‐\ncessed.\n\nDMEVENTDTHINPOOLMETADATA\nVariable is set by thin plugin and is available to executed program. Value present ac‐\ntual  usage of thin pool metadata volume. Variable is not set when error event is pro‐\ncessed.\n\nDMEVENTDVDOPOOL\nVariable is set by vdo plugin and is available to executed program. Value present  ac‐\ntual usage of VDO pool data volume. Variable is not set when error event is processed.\n\nLVMRUNBYDMEVENTD\nVariable  is set by thin and vdo plugin to prohibit recursive interation with dmeventd\nby any executed lvm2 command from a thincommand, vdocommand environment.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "lvm(8), lvm.conf(5)\n\n\n\nRed Hat Inc                       DM TOOLS 2.03.11(2) (2021-01-08)                       DMEVENTD(8)",
            "subsections": []
        }
    },
    "summary": "dmeventd — Device-mapper event daemon",
    "flags": [
        {
            "flag": "-d",
            "long": null,
            "arg": null,
            "description": "Repeat from 1 to 3 times ( -d, -dd, -ddd ) to increase the detail of debug messages sent to syslog. Each extra d adds more debugging information."
        },
        {
            "flag": "-f",
            "long": null,
            "arg": null,
            "description": "Don't fork, run in the foreground."
        },
        {
            "flag": "-h",
            "long": null,
            "arg": null,
            "description": "Show help information."
        },
        {
            "flag": "-l",
            "long": null,
            "arg": null,
            "description": "Log through stdout and stderr instead of syslog. This option works only with option -f, otherwise it is ignored. -? Show help information on stderr."
        },
        {
            "flag": "-R",
            "long": null,
            "arg": null,
            "description": "Replace a running dmeventd instance. The running dmeventd must be version 2.02.77 or newer. The new dmeventd instance will obtain a list of devices and events to monitor from the currently running daemon."
        },
        {
            "flag": "-V",
            "long": null,
            "arg": null,
            "description": "Show version of dmeventd."
        }
    ],
    "examples": [],
    "see_also": [
        {
            "name": "lvm",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/lvm/8/json"
        },
        {
            "name": "lvm.conf",
            "section": "5",
            "url": "https://www.chedong.com/phpMan.php/man/lvm.conf/5/json"
        }
    ]
}