Hotplug

Procd (the init system and process management daemon) executes scripts located in /etc/hotplug.d when certain events happen, like for example when an interface goes up or down, when a new storage drive is detected, or when a button is pressed. It can be very useful with PPPoE connection or in an unstable network, or to use hardware buttons.

This functionality emulates/extends what was done by the long retired Hotplug2 package.

In the /etc/hotplug.d directory you will find some directories block, iface, net and ntp.

When the trigger event fires, Procd will execute all scripts in that trigger's directory, in alphabetical order. Which is why most scripts in there use a numeric prefix.

Directory Description
block Block device events: device connected/disconnected
button Buttons: not created by default, see /etc/rc.button instead
dhcp DHCP-related events
dsl DSL modem events
firewall Firewall-related events
iface Interface events: LAN/WAN/etc. is connected/disconnected
neigh Neighbor discovery
net Network-related events
ntp Time sync events: time step, time server stratum change
tftp TFTP-related events
usb USB devices like 3g-modem and tty*
usbmisc Special USB peripherals like printers (scripts in this subsystem have fewer variables available)

See also:

Simply place your script(s) into the right hotplug.d directory, if there is none just create the right one.

Procd exposes a wealth of info when executes your scripts in /etc/hotplug.d, usually as environmental variables.

If you want to see what environmental variables it is providing, make a script like this:

cat << "EOF" > /etc/hotplug.d/iface/00-logger
logger -t hotplug $(env)
EOF

Then trigger the event connected to that directory, and then you can see what envs were passed by reading the output:

logread -e hotplug

For scripts in net directory, these are the (relevant) environmental variables

Variable name Description
ACTION “add” or “remove” noted
DEVICENAME configured interface names (br-lan, wlan0, phy1-ap0
PATH Full path
DEVPATH full device path (for example “/devices/pci0000:00/0000:00:0b.0/usb1/1-1/1-1:1.0/host7/target7:0:0/7:0:0:0/block/sdc/sdc1 ”
DEVTYPE what the DEVICENAME are names of, ie. br-lan, phy1-ap0
INTERFACE configured interfaces as in DEVTYPE
SEQNUM seqnum (a number)
SUBSYSTEM always = “net”
IFINDEX appears to be related to the configured interfaces. See `ifconfig`

For scripts in block directory, these are the (relevant) environmental variables

Variable name Description
ACTION For normal device (e.g: sda) it is either “add” or “remove”. Can be “change” if the device is dm-crypt (e.g: dm-0)
DEVICENAME seems same as DEVNAME below
DEVNAME Device or partition name (if I connect a drive I get a hotplug call with “sda” and another hotplug call with “sda1”)
DEVPATH full device path (for example “/devices/pci0000:00/0000:00:0b.0/usb1/1-1/1-1:1.0/host7/target7:0:0/7:0:0:0/block/sdc/sdc1 ”
DEVTYPE what the DEVNAME e DEVICENAME are names of, I've seen “partition” here when a device with a readable partition is inserted and a “disk” when that device is removed.
MAJOR major device number
MINOR minor device number
SEQNUM seqnum (a number)
SUBSYSTEM seems this is only “block”

For scripts in dsl directory, these are the (relevant) environment variables

Variable name Description
DSL_NOTIFICATION_TYPE DSL_STATUS, DSL_INTERFACE_STATUS, DSL_DATARATE_STATUS_US, DSL_DATARATE_STATUS_DS
DSL_LINE_NUMBER 0, 1 *

When DSL_NOTIFICATION_TYPE is DSL_STATUS, the following environment variables are set

Variable name Description
DSL_XTU_STATUS ADSL, VDSL
DSL_TC_LAYER_STATUS ATM, EFM
DSL_EFM_TC_CONFIG_US NORMAL, PRE_EMPTION, UNKNOWN
DSL_EFM_TC_CONFIG_DS NORMAL, UNKNOWN

When DSL_NOTIFICATION_TYPE is DSL_INTERFACE_STATUS, the following environment variables are set

Variable name Description
DSL_INTERFACE_STATUS DOWN, READY, HANDSHAKE, TRAINING, UP
DSL_BONDING_STATUS INACTIVE, ACTIVE *

When DSL_NOTIFICATION_TYPE is DSL_DATARATE_STATUS_US, the following environment variables are set

Variable name Description
DSL_DATARATE_US_BC0 Upstream data rate in bit/s for Channel 0
DSL_DATARATE_US_BC1 Upstream data rate in bit/s for Channel 1 *

When DSL_NOTIFICATION_TYPE is DSL_DATARATE_STATUS_DS, the following environment variables are set

Variable name Description
DSL_DATARATE_DS_BC0 Downstream data rate in bit/s for Channel 0
DSL_DATARATE_DS_BC1 Downstream data rate in bit/s for Channel 1 *

NOTE: environment variables marked with an * are only available when channel bonding support is compiled in.

For scripts in iface directory, these are the (relevant) environmental variables

Variable name Description
ACTION ifdown, ifup, ifup-failed, ifupdate, free, reload, iflink, create
INTERFACE Name of the logical interface which went up or down (e.g. wan or lan)
DEVICE Name of the physical device which went up or down (e.g. eth0 or br-lan or pppoe-wan), when applicable

The meaning of most actions should be straightforward, the maybe-not-obvious ones are:

Value Description
ifup-failed ifdown event happened while the interface was being brought up
free the interface has been removed (inverse of create)
iflink the interface reported the presence of a carrier

When ACTION is ifupdate, the following environment variables may be set

Variable name Description
IFUPDATE_ADDRESSES 1 if address changed since previous ifupdate event
IFUPDATE_ROUTES 1 if a route changed since previous ifupdate event
IFUPDATE_PREFIXES 1 if prefix changed since previous ifupdate event
IFUPDATE_DATA 1 if ubus call network.interface.$INTERFACE set_data ... (or equivalent) happened

Variables based on busybox ntpd:

Variable name description
ACTION step, stratum, unsync or periodic
freq_drift_ppm ntp variables
offset Time adjustment done
stratum Quality (nr of servers to atomic clock)
poll_interval ntp variables

Even without NTP sync, you will receive a “periodic” hotplug event, with stratum=16, about every 11 minutes out of the box.

Variable name description
ACTION add, remove, bind, unbind as above
DEVICENAME eg “1-1”
DEVNAME eg, “bus/usb/001/002”
DEVNUM eg 002
DEVPATH eg, “/devices/platform/ehci-platform/usb1/1-1”
DEVTYPE eg “usb_device”
TYPE eg 9/0/1
PRODUCT the vendor/productcode/version, eg “424/2640/0” see lsusb
SEQNUM (action number since boot for this subsystem) eg 335
BUSNUM eg 001
MAJOR eg 189
MINOR eg 1
Variable name description
ACTION add, remove as above
DEVNAME eg, “bus/usb/001/002”
DEVPATH eg, “/devices/platform/ehci-platform/usb1/1-1”
DEVICENAME eg “1-1”
SEQNUM (action number since boot for this subsystem) eg 335
MAJOR eg 189
MINOR eg 1
cat << "EOF" > /etc/hotplug.d/iface/99-my-action
[ "${ACTION}" = "ifup" ] && {
    logger -t hotplug "Device: ${DEVICE} / Action: ${ACTION}"
} 
EOF

Every time an interface goes up then the if/fi statement will be executed.

An other script to create a symlink instead of renaming the device. I test if DEVICE_NAME is empty because when I plug usb device I retrieve two add event, and the first come before created device, so symlink fails.

cat << "EOF" > /etc/hotplug.d/usb/20-cp210x
CP210_PRODID="10c4/ea60/100"
SYMLINK="my_link"
 
if [ "${PRODUCT}" = "${CP210_PRODID}" ]; then
    if [ "${ACTION}" = "add" ]; then
          DEVICE_NAME=$(ls /sys/${DEVPATH} | grep tty)
          if [ -z ${DEVICE_NAME} ]; then
              logger -t hotplug "Warning DEVICE_NAME is empty"
              exit 0
          fi
          logger -t hotplug "Device name of cp210 is ${DEVICE_NAME}"
          ln -s /dev/${DEVICE_NAME} /dev/${SYMLINK}
          logger -t hotplug "Symlink from /dev/${DEVICE_NAME} to /dev/${SYMLINK} created"
    fi
fi
 
if [ "${PRODUCT}" = "${CP210_PRODID}" ]; then
    if [ "${ACTION}" = "remove" ]; then
        rm /dev/${SYMLINK}
        logger -t hotplug "Symlink /dev/${SYMLINK} removed"
    fi
fi
EOF
cat << "EOF" > /etc/hotplug.d/usb/20-bt_test
BT_PRODID="a12/1/"
BT_PRODID_HOT="${PRODUCT::6}"
 
#logger -t hotplug "PRODUCT ID is ${BT_PRODID_HOT}"
 
if [ "${BT_PRODID_HOT}" = "${BT_PRODID}" ]; then
    if [ "${ACTION}" = "add" ]; then
        logger -t hotplug "bluetooth device has been plugged in!"
        if [ "${BSBTID_NEW}" = "${BSBTID_OLD}" ]; then
            logger -t hotplug "bluetooth device hasn't changed"
        else
            logger -t hotplug "bluetooth device has changed"
        fi
    fi
    if [ "${ACTION}" = "remove" ]; then
        logger -t hotplug "bluetooth device has been removed!"
    fi
else
    logger -t hotplug "USB device is not bluetooth"
fi
EOF
cat << "EOF" > /etc/hotplug.d/usb/20-mjpg_start
case "${ACTION}" in
    add)
            # start process
        service mjpg-streamer start
            ;;
    remove)
            # stop process
        service mjpg-streamer stop
            ;;
esac
EOF
cat << "EOF" > /etc/hotplug.d/block/xfs_automount
# if a new block device is connected
if [ "${ACTION}" = "add" ]; then
    # getting device UUID
    detected_uuid="$(xfs_admin -u /dev/${DEVICENAME} | awk '{print $3}')"
    # deciding mountpoint for known UUID
    mountpoint=""
    case "${detected_uuid}" in
        6a5d7c5c-c9d0-41cc-8f19-78d97f839c05)
            mountpoint="/path/to/first/mountpoint"
            ;;
        02880b1f-0c67-46b6-9b05-5535680ccc89)
            mountpoint="/path/to/second/mountpoint"
            ;;
    esac
 
    # if we have a known UUID we have a mountpoint so we can mount it
    if [ "${mountpoint}" != "" ]; then 
        mount /dev/${DEVICENAME} ${mountpoint}
    fi
fi
# unmounting happens automatically at device disconnection anyway so no logic for that
EOF

You may have noticed that the udev and eudev were removed in the openwrt 18.0.* release. Don't worry, because you still can make things work. You can use hotplug scripts as coldplug. Pay attention to the ACTION environment variable, at boot 'bind' actions are executed. So, just add this option to hotplug and run accordingly.

In my case I used this:

mkdir -p /etc/hotplug.d/usb
cat << "EOF" > /etc/hotplug.d/usb/22-symlinks
# Description: Action executed on boot (bind) and with the system on the fly
if [ "${ACTION}" = "bind" ]; then
  case "${PRODUCT}" in
    1bc7*) # Telit HE910 3g modules product id prefix
      DEVICE_NAME="$(ls /sys/${DEVPATH} | grep tty)"
      DEVICE_TTY="$(ls /sys/${DEVPATH}/tty/)"
      # Module Telit HE910-* connected to minipciexpress slot MAIN
      if [ "${DEVICENAME}" = "1-1.3:1.0" ]; then
        ln -s /dev/${DEVICE_TTY} /dev/ttyMODULO1_DIAL
        logger -t hotplug "Symlink from /dev/${DEVICE_TTY} to /dev/ttyMODULO1_DIAL created"
      elif [ "${DEVICENAME}" = "1-1.3:1.6" ]; then
        ln -s /dev/${DEVICE_TTY} /dev/ttyMODULO1_DATA
        logger -t hotplug "Symlink from /dev/${DEVICE_TTY} to /dev/ttyMODULO1_DATA created"
      # Module Telit HE910-* connected to minipciexpress slot SECONDARY
      elif [ "${DEVICENAME}" = "1-1.2:1.0" ]; then
        ln -s /dev/${DEVICE_TTY} /dev/ttyMODULO2_DIAL
        logger -t hotplug "Symlink from /dev/${DEVICE_TTY} to /dev/ttyMODULO2_DIAL created"
      elif [ "${DEVICENAME}" = "1-1.2:1.6" ]; then
        ln -s /dev/${DEVICE_TTY} /dev/ttyMODULO2_DATA
        logger -t hotplug "Symlink from /dev/${DEVICE_TTY} to /dev/ttyMODULO2_DATA created"
      fi
    ;;
  esac
fi
# Action to remove the symlinks
if [ "${ACTION}" = "remove" ]; then
  case "${PRODUCT}" in
    1bc7*)  # Telit HE910 3g modules product id prefix
     # Module Telit HE910-* connected to minipciexpress slot MAIN
      if [ "${DEVICENAME}" = "1-1.3:1.0" ]; then
        rm /dev/ttyMODULO1_DIAL
        logger -t hotplug "Symlink /dev/ttyMODULO1_DIAL removed"
      elif [ "${DEVICENAME}" = "1-1.3:1.6" ]; then
        rm /dev/ttyMODULO1_DATA
        logger -t hotplug "Symlink /dev/ttyMODULO1_DATA removed"
      # Module Telit HE910-* connected to minipciexpress slot SECONDARY
      elif [ "${DEVICENAME}" = "1-1.2:1.0" ]; then
        rm /dev/ttyMODULO2_DIAL
        logger -t hotplug "Symlink /dev/ttyMODULO2_DIAL removed"
      elif [ "${DEVICENAME}" = "1-1.2:1.6" ]; then
        rm /dev/ttyMODULO2_DATA
        logger -t hotplug "Symlink /dev/ttyMODULO2_DATA removed"
      fi
    ;;
  esac
fi
EOF

If you have a DSL modem you can add logging of DSL status changes and connection data rates.

This can be helpful if your DSL connection is affected by Seamless Rate Adaptation (SRA) or Dynamic Line Management (DLM) events; for SRA events data rate changes will be logged, while for DLM events connection status changes will be logged as the modem is forced to retrain and then the new data rates will be logged.

cat << "EOF" > /etc/hotplug.d/dsl/20-dsl_status
case "${DSL_NOTIFICATION_TYPE}" in
(DSL_INTERFACE_STATUS)
logger -p daemon.notice -t dsl-notify "${DSL_XTU_STATUS} link status: ${DSL_INTERFACE_STATUS}" ;;
(DSL_DATARATE_STATUS_US)
logger -p daemon.notice -t dsl-notify "DSL upstream actual data rate: ${DSL_DATARATE_US_BC0}" ;;
(DSL_DATARATE_STATUS_DS)
logger -p daemon.notice -t dsl-notify "DSL downstream actual data rate: ${DSL_DATARATE_DS_BC0}" ;;
esac
EOF

This script assumes that channel bonding is not compiled in to the DSL support.

Restart Wi-Fi when plugging in a wireless USB adapter.

mkdir -p /etc/hotplug.d/usb
cat << "EOF" > /etc/hotplug.d/usb/20-rtl8188su
if [ "${PRODUCT}" = "bda/8171/200" ] \
&& [ "${ACTION}" = "add" ]
then wifi
fi
EOF

The above code matches the following device.

# lsusb -v
	idVendor	0x0bda Realtek Semiconductor Corp.
	idProduct	0x8171 RTL8188SU 802.11n WLAN Adapter
	bcdDevice	2.00

Assuming your ISP provides a dynamic IP address. Reconnect until you get the one matching a specific regexp. Delay for 10 seconds between reconnects. Set up Hotplug extras to trigger the script upon connecting WAN interface.

mkdir -p /etc/hotplug.d/online
cat << "EOF" > /etc/hotplug.d/online/10-wan-ipaddr
. /lib/functions/network.sh
network_flush_cache
network_find_wan WAN_IF
network_get_ipaddr WAN_ADDR "${WAN_IF}"
if [ "${WAN_IF}" != "${INTERFACE}" ]
then exit 0
fi
case ${WAN_ADDR} in
(??.???.*) exit 0 ;;
esac
sleep 10
ifup ${INTERFACE}
EOF

Assuming pre-configured upstream interfaces wana and wanb. Set up persistent interface names by MAC address.

cat << "EOF" > /etc/hotplug.d/iface/00-dev-rename
dev_rename() {
local DEV_CONF="${1}"
local DEV_MAC DEV_NAME DEV_ONAME
config_get DEV_MAC "${DEV_CONF}" mac
config_get DEV_NAME "${DEV_CONF}" name
DEV_ONAME="$(grep -l -e "${DEV_MAC}" \
$(find /sys/class/net/*/device/uevent \
| sed -e "s|/device/uevent$|/address|") \
| awk -F '/' '{print $5}')"
if [ -n "${DEV_MAC}" ] \
&& [ "${DEV_ONAME}" != "${DEV_NAME}" ]
then ip link set "${DEV_ONAME}" name "${DEV_NAME}"
fi
}
. /lib/functions.sh
config_load network
config_foreach dev_rename device
EOF
 
while read -r DEV_NAME DEV_MAC
do
uci set network.${DEV_NAME}.device="${DEV_NAME}"
uci set network.${DEV_NAME}6.device="${DEV_NAME}"
uci -q delete network.${DEV_NAME}_dev
uci set network.${DEV_NAME}_dev="device"
uci set network.${DEV_NAME}_dev.mac="${DEV_MAC}"
uci set network.${DEV_NAME}_dev.name="${DEV_NAME}"
done << EOI
wana 11:22:33:44:55:66
wanb aa:bb:cc:dd:ee:ff
EOI
uci commit network
service network restart
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  • Last modified: 2024/01/15 17:01
  • by systemcrash