{
    "mode": "man",
    "parameter": "systemd-udevd",
    "section": "8",
    "url": "https://www.chedong.com/phpMan.php/man/systemd-udevd/8/json",
    "generated": "2026-08-17T16:24:40Z",
    "synopsis": "systemd-udevd.service\nsystemd-udevd-control.socket\nsystemd-udevd-kernel.socket\n/usr/lib/systemd/systemd-udevd [--daemon] [--debug] [--children-max=] [--exec-delay=]\n[--event-timeout=] [--resolve-names=early|late|never]\n[--version] [--help]",
    "sections": {
        "NAME": {
            "content": "systemd-udevd.service, systemd-udevd-control.socket, systemd-udevd-kernel.socket, systemd-\nudevd - Device event managing daemon\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "systemd-udevd.service\n\nsystemd-udevd-control.socket\n\nsystemd-udevd-kernel.socket\n\n/usr/lib/systemd/systemd-udevd [--daemon] [--debug] [--children-max=] [--exec-delay=]\n[--event-timeout=] [--resolve-names=early|late|never]\n[--version] [--help]\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "systemd-udevd listens to kernel uevents. For every event, systemd-udevd executes matching\ninstructions specified in udev rules. See udev(7).\n\nThe behavior of the daemon can be configured using udev.conf(5), its command line options,\nenvironment variables, and on the kernel command line, or changed dynamically with udevadm\ncontrol.\n",
            "subsections": []
        },
        "OPTIONS": {
            "content": "",
            "subsections": [
                {
                    "name": "-d --daemon",
                    "content": "Detach and run in the background.\n\nAdded in version 186.\n",
                    "flag": "-d",
                    "long": "--daemon"
                },
                {
                    "name": "-D --debug",
                    "content": "Print debug messages to standard error.\n\nAdded in version 186.\n",
                    "flag": "-D",
                    "long": "--debug"
                },
                {
                    "name": "-c --children-max=",
                    "content": "Limit the number of events executed in parallel.\n\nAdded in version 186.\n",
                    "flag": "-c"
                },
                {
                    "name": "-e --exec-delay=",
                    "content": "Delay the execution of each RUN{program} parameter by the given number of seconds. This\noption might be useful when debugging system crashes during coldplug caused by loading\nnon-working kernel modules.\n\nAdded in version 186.\n",
                    "flag": "-e"
                },
                {
                    "name": "-t --event-timeout=",
                    "content": "Set the number of seconds to wait for events to finish. After this time, the event will\nbe terminated. The default is 180 seconds.\n\nAdded in version 216.\n",
                    "flag": "-t"
                },
                {
                    "name": "-s --timeout-signal=",
                    "content": "Set the signal which systemd-udevd will send to forked off processes after reaching event\ntimeout. The setting can be overridden at boot time with the kernel command line option\nudev.timeoutsignal=. Setting to SIGABRT may be helpful in order to debug worker\ntimeouts. Defaults to SIGKILL. Note that setting the option on the command line overrides\nthe setting from the configuration file.\n\nAdded in version 246.\n",
                    "flag": "-s"
                },
                {
                    "name": "-N --resolve-names=",
                    "content": "Specify when systemd-udevd should resolve names of users and groups. When set to early\n(the default), names will be resolved when the rules are parsed. When set to late, names\nwill be resolved for every event. When set to never, names will never be resolved and all\ndevices will be owned by root.\n\nAdded in version 186.\n",
                    "flag": "-N"
                },
                {
                    "name": "-h --help",
                    "content": "Print a short help text and exit.\n",
                    "flag": "-h",
                    "long": "--help"
                },
                {
                    "name": "--version",
                    "content": "Print a short version string and exit.\n",
                    "long": "--version"
                }
            ]
        },
        "KERNEL COMMAND LINE": {
            "content": "Parameters prefixed with \"rd.\" will be read when systemd-udevd is used in an initrd, those\nwithout will be processed both in the initrd and on the host.\n\nudev.loglevel=, rd.udev.loglevel=\nSet the log level.\n\nAdded in version 247.\n\nudev.childrenmax=, rd.udev.childrenmax=\nLimit the number of events executed in parallel.\n\nAdded in version 186.\n\nudev.execdelay=, rd.udev.execdelay=\nDelay the execution of each RUN{program} parameter by the given number of seconds. This\noption might be useful when debugging system crashes during coldplug caused by loading\nnon-working kernel modules.\n\nAdded in version 186.\n\nudev.eventtimeout=, rd.udev.eventtimeout=\nWait for events to finish up to the given number of seconds. This option might be useful\nif events are terminated due to kernel drivers taking too long to initialize.\n\nAdded in version 216.\n\nudev.timeoutsignal=, rd.udev.timeoutsignal=\nSpecifies a signal that systemd-udevd will send to workers on timeout. Note that kernel\ncommand line option overrides both the setting in the configuration file and the one on\nthe program command line.\n\nAdded in version 246.\n\nudev.blockdevreadonly, rd.udev.blockdevreadonly\nIf specified, mark all physical block devices read-only as they appear. Synthetic block\ndevices (such as loopback block devices or device mapper devices) are left as they are.\nThis is useful to guarantee that the contents of physical block devices remains\nunmodified during runtime, for example to implement fully stateless systems, for testing\nor for recovery situations where corrupted file systems shall not be corrupted further\nthrough accidental modification.\n\nA block device may be marked writable again by issuing the blockdev --setrw command, see\nblockdev(8) for details.\n\nAdded in version 246.\n\nnet.ifnames=\nNetwork interfaces are renamed to give them predictable names when possible. It is\nenabled by default; specifying 0 disables it.\n\nAdded in version 199.\n\nnet.naming-scheme=\nNetwork interfaces are renamed to give them predictable names when possible (unless\nnet.ifnames=0 is specified, see above). With this kernel command line option it is\npossible to pick a specific version of this algorithm and override the default chosen at\ncompilation time. Expects one of the naming scheme identifiers listed in systemd.net-\nnaming-scheme(7), or \"latest\" to select the latest scheme known (to this particular\nversion of systemd-udevd.service).\n\nNote that selecting a specific scheme is not sufficient to fully stabilize interface\nnaming: the naming is generally derived from driver attributes exposed by the kernel. As\nthe kernel is updated, previously missing attributes systemd-udevd.service is checking\nmight appear, which affects older name derivation algorithms, too.\n\nAdded in version 240.\n\nnet.ifname-policy=policy1[,policy2,...][,MAC]\nSpecifies naming policies applied when renaming network interfaces. Takes a list of\npolicies and an optional MAC address separated with comma. Each policy value must be one\nof the policies understood by the NamePolicy= setting in .link files, e.g.  \"onboard\" or\n\"path\". See systemd.link(5) for more details. When the MAC address is specified, the\npolicies are applied to the interface which has the address. When no MAC address is\nspecified, the policies are applied to all interfaces. This kernel command line argument\ncan be specified multiple times.\n\nThis argument is not directly read by systemd-udevd, but is instead converted to a .link\nfile by systemd-network-generator.service(8). For this argument to take effect,\nsystemd-network-generator.service must be enabled.\n\nExample:\n\nnet.ifname-policy=keep,kernel,path,slot,onboard,01:23:45:67:89:ab\nnet.ifname-policy=keep,kernel,path,slot,onboard,mac\n\nThis is mostly equivalent to creating the following .link files:\n\n# 91-name-policy-with-mac.link\n[Match]\nMACAddress=01:23:45:67:89:ab\n\n[Link]\nNamePolicy=keep kernel path slot onboard\nAlternativeNamePolicy=path slot onboard\n\nand\n\n# 92-name-policy-for-all.link\n[Match]\nOriginalName=*\n\n[Link]\nNamePolicy=keep kernel path slot onboard mac\nAlternativeNamePolicy=path slot onboard mac\n\nAdded in version 250.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "udev.conf(5), udev(7), udevadm(8)\n\nsystemd 255                                                                 SYSTEMD-UDEVD.SERVICE(8)",
            "subsections": []
        }
    },
    "summary": "systemd-udevd.service, systemd-udevd-control.socket, systemd-udevd-kernel.socket, systemd- udevd - Device event managing daemon",
    "flags": [
        {
            "flag": "-d",
            "long": "--daemon",
            "arg": null,
            "description": "Detach and run in the background. Added in version 186."
        },
        {
            "flag": "-D",
            "long": "--debug",
            "arg": null,
            "description": "Print debug messages to standard error. Added in version 186."
        },
        {
            "flag": "-c",
            "long": null,
            "arg": null,
            "description": "Limit the number of events executed in parallel. Added in version 186."
        },
        {
            "flag": "-e",
            "long": null,
            "arg": null,
            "description": "Delay the execution of each RUN{program} parameter by the given number of seconds. This option might be useful when debugging system crashes during coldplug caused by loading non-working kernel modules. Added in version 186."
        },
        {
            "flag": "-t",
            "long": null,
            "arg": null,
            "description": "Set the number of seconds to wait for events to finish. After this time, the event will be terminated. The default is 180 seconds. Added in version 216."
        },
        {
            "flag": "-s",
            "long": null,
            "arg": null,
            "description": "Set the signal which systemd-udevd will send to forked off processes after reaching event timeout. The setting can be overridden at boot time with the kernel command line option udev.timeoutsignal=. Setting to SIGABRT may be helpful in order to debug worker timeouts. Defaults to SIGKILL. Note that setting the option on the command line overrides the setting from the configuration file. Added in version 246."
        },
        {
            "flag": "-N",
            "long": null,
            "arg": null,
            "description": "Specify when systemd-udevd should resolve names of users and groups. When set to early (the default), names will be resolved when the rules are parsed. When set to late, names will be resolved for every event. When set to never, names will never be resolved and all devices will be owned by root. Added in version 186."
        },
        {
            "flag": "-h",
            "long": "--help",
            "arg": null,
            "description": "Print a short help text and exit."
        },
        {
            "flag": "",
            "long": "--version",
            "arg": null,
            "description": "Print a short version string and exit."
        }
    ],
    "examples": [],
    "see_also": [
        {
            "name": "udev.conf",
            "section": "5",
            "url": "https://www.chedong.com/phpMan.php/man/udev.conf/5/json"
        },
        {
            "name": "udev",
            "section": "7",
            "url": "https://www.chedong.com/phpMan.php/man/udev/7/json"
        },
        {
            "name": "udevadm",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/udevadm/8/json"
        },
        {
            "name": "SYSTEMD-UDEVD.SERVICE",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/SYSTEMD-UDEVD.SERVICE/8/json"
        }
    ]
}