Ubuntu – How to detect insertion of DVD disc

automountdvdudev

In particular, how to catch it for the purposes of automounting the DVD filesystem?

Update in response to Oli's answer:

udev seems to be able to detect the insertion of DVD, as demonstrated by changes in udevadm's output before and after the event:

% udevadm info -q env -n /dev/cdrom

which results in additional environment variables as follows:

ID_CDROM_MEDIA=1
ID_CDROM_MEDIA_DVD=1
ID_CDROM_MEDIA_SESSION_COUNT=1
ID_CDROM_MEDIA_STATE=complete
ID_CDROM_MEDIA_TRACK_COUNT=1
ID_CDROM_MEDIA_TRACK_COUNT_DATA=1
ID_FS_LABEL=20130926_Backup
ID_FS_LABEL_ENC=20130926_Backup
ID_FS_TYPE=udf
ID_FS_USAGE=filesystem

However, when I tried the following udev rule (which tries to detect ID_FS_TYPE=="udf"),

SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{ID_FS_TYPE}=="udf", ENV{ID_PATH}=="pci-0000:00:1f.2-scsi-0:0:0:0", ACTION=="add", RUN+="/bin/mount -t udf -o ro /dev/cdrom /var/run/usbmount/dvdrom"

it doesn't work. What could be the problem?

Solution

Was finally able to solve this thanks to Oli's suggestions:

/etc/udev/rules.d/autodvd.rules:

SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{ID_PATH}=="pci-0000:00:1f.2-scsi-0:0:0:0", ACTION=="change", RUN+="/usr/local/bin/autodvd"

/usr/local/bin/autodvd:

#!/bin/bash
{
  if [ $ID_CDROM_MEDIA -eq 1 ]; then
    mkdir -p /var/run/usbmount/dvdrom
    mount -t $ID_FS_TYPE -o ro /dev/cdrom /var/run/usbmount/dvdrom
  else
    umount -l /var/run/usbmount/dvdrom
    rm -rf /var/run/usbmount/dvdrom
  fi
} &>> "/var/log/autodvd.log" &

Apparently ACTION=="add" isn't triggered when DVD disc is inserted. So instead, we use ACTION=="change" and then detect the insert or eject event via scripting.

Best Answer

UDEV sends out events for CD/DVD drives (I've just tested it with udevadm) so you should be able to either write a UDEV script or write an upstart script like so:

start on block-device-added

task

script
   if [ `$DEV` -eq "/dev/sr0" ]; then
      # do something
   fi
end script

You might have to be careful about checking its mount status. I'm pillaging this from a similar answer of mine which is a bit more explanatory.

When running udevadm monitor --property --udev, here is the output I got when putting in a DVD (--property makes this quite verbose but it lets you know exactly what you're dealing with):

UDEV  [2251414.166711] change   /devices/pci0000:00/0000:00:1c.1/0000:07:00.0/ata17/host16/target16:0:0/16:0:0:0/block/sr0 (block)
ACTION=change
DEVLINKS=/dev/cdrom /dev/cdrw /dev/disk/by-id/ata-Optiarc_DVD_RW_AD-7240S /dev/disk/by-label/UT2004_DVD /dev/disk/by-path/pci-0000:07:00.0-scsi-0:0:0:0 /dev/dvd /dev/dvdrw
DEVNAME=/dev/sr0
DEVPATH=/devices/pci0000:00/0000:00:1c.1/0000:07:00.0/ata17/host16/target16:0:0/16:0:0:0/block/sr0
DEVTYPE=disk
DISK_MEDIA_CHANGE=1
GENERATED=1
ID_ATA=1
ID_ATA_SATA=1
ID_ATA_SATA_SIGNAL_RATE_GEN1=1
ID_BUS=ata
ID_CDROM=1
ID_CDROM_CD=1
ID_CDROM_CD_R=1
ID_CDROM_CD_RW=1
ID_CDROM_DVD=1
ID_CDROM_DVD_PLUS_R=1
ID_CDROM_DVD_PLUS_RW=1
ID_CDROM_DVD_PLUS_R_DL=1
ID_CDROM_DVD_R=1
ID_CDROM_DVD_RAM=1
ID_CDROM_DVD_RW=1
ID_CDROM_MEDIA=1
ID_CDROM_MEDIA_DVD=1
ID_CDROM_MEDIA_SESSION_COUNT=1
ID_CDROM_MEDIA_STATE=complete
ID_CDROM_MEDIA_TRACK_COUNT=1
ID_CDROM_MEDIA_TRACK_COUNT_DATA=1
ID_CDROM_MRW=1
ID_CDROM_MRW_W=1
ID_FS_LABEL=UT2004_DVD
ID_FS_LABEL_ENC=UT2004_DVD
ID_FS_TYPE=iso9660
ID_FS_USAGE=filesystem
ID_FS_VERSION=Joliet\x20Extension
ID_MODEL=Optiarc_DVD_RW_AD-7240S
ID_MODEL_ENC=Optiarc\x20DVD\x20RW\x20AD-7240S\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
ID_PATH=pci-0000:07:00.0-scsi-0:0:0:0
ID_PATH_TAG=pci-0000_07_00_0-scsi-0_0_0_0
ID_REVISION=1.00
ID_SERIAL=Optiarc_DVD_RW_AD-7240S
ID_TYPE=cd
MAJOR=11
MINOR=0
SEQNUM=4400
SUBSYSTEM=block
TAGS=:udev-acl:
UDEV_LOG=3
UDISKS_PRESENTATION_NOPOLICY=0
USEC_INITIALIZED=10393360
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