Udev rules and group / permission errors [solved] [outdated]

Question

Latest udev is a miracle to me. It ignores every group ore permission settings. Anyone else having same experiences?
Last edited by Moo-Crumpus (2008-09-29 05:17:40)

Answer 1

Let's assume that you have two files with udev rules. The basic udev.rules and 00.udev.rules (with custom rules).
Udev first reads all rules from 00 file and then rules from the basic file.
This means that if you have a custom rule for a given device you should copy all rules that apply to it from the basic file to the 00 file (not only lines with GROUP). This is because with OPTIONS="last_rule" udev will stop processing rules for this device.
All rules are read and then applied in the order from the top to bottom except SUBSYTEM which is applied as the last rule (kind of held in a buffer). This is the reason why my cd burner /dev/hdc had permissions for disk group and not optical.
This is my 00.udev.rules (it still needs some cosmetic changes but it works and of course I don't have all the devices):
SUBSYSTEM="video4linux", GROUP="users"
SUBSYSTEM="sound", GROUP="users"
SUBSYSTEM="printer", GROUP="users"
SUBSYSTEM="block", GROUP="disk"
BUS="ide", KERNEL="hd[a-z]", PROGRAM="/etc/udev/cdsymlinks.sh %k", SYMLINK="%c{1} %c{2} %c{3} %c{4} %c{5} %c{6}"
BUS="ide", KERNEL="hd*", PROGRAM="/etc/udev/ide-devfs.sh %k %b %n", SYMLINK="%c{1} %c{2}"
BUS="ide", KERNEL="hdc", SYSFS{removable}="1", PROGRAM="/bin/cat /proc/ide/%k/media", RESULT="cdrom*", NAME="%k", GROUP="users", SYMLINK="nagrywarka dvd cdrw", OPTIONS="last_rule"
BUS="ide", KERNEL="hd[a-z]", SYSFS{removable}="1", PROGRAM="/bin/cat /proc/ide/%k/media", RESULT="cdrom*", NAME="%k", GROUP="users", OPTIONS="last_rule"
BUS="ide", KERNEL="hd*", PROGRAM="/etc/udev/ide-floppy.sh %k", RESULT="floppy", NAME{all_partitions}="%k", GROUP="users", OPTIONS="last_rule"
BUS="scsi", KERNEL="sr[0-9]*", PROGRAM="/etc/udev/cdsymlinks.sh %k", SYMLINK="%c{1} %c{2} %c{3} %c{4} %c{5} %c{6}"
BUS="scsi", KERNEL="scd[0-9]*", PROGRAM="/etc/udev/cdsymlinks.sh %k", SYMLINK="%c{1} %c{2} %c{3} %c{4} %c{5} %c{6}"
BUS="scsi", KERNEL="sr[0-9]*", SYSFS{type}="5", NAME="scd%n", GROUP="users", OPTIONS="last_rule"
BUS="scsi", KERNEL="sg[0-9]*", SYSFS{type}="5", NAME="%k", GROUP="users", OPTIONS="last_rule"
KERNEL="fd[0-9]*", NAME="fd%n", GROUP="users", SYMLINK="floppy/%n fd%nu1440 fd%nu720 fd%nh1200 fd%nu360", OPTIONS="last_rule"
BUS="usb", SYSFS{serial}="CN16J1Q3HWSX", KERNEL="lp[0-9]*", NAME="usb/%k", GROUP="users", SYMLINK="drukarka_hp_845c drukarka", OPTIONS="last_rule"
BUS="usb", KERNEL="sd*", PROGRAM="/etc/udev/usb-storage.sh %k", RESULT="1", NAME="%k", GROUP="users", OPTIONS="last_rule"
KERNEL="rtc", NAME="misc/%k", SYMLINK="%k", GROUP="users", MODE="0664", OPTIONS="last_rule"
KERNEL="agpgart", NAME="misc/%k", SYMLINK="%k" GROUP="users", OPTIONS="last_rule"
KERNEL="nvidia*", GROUP="users", OPTIONS="last_rule"
KERNEL="fb[0-9]*", NAME="fb/%n", GROUP="users", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="card[0-9]*", NAME="dri/%k", GROUP="users", OPTIONS="last_rule"
KERNEL="3dfx*", NAME="%k", GROUP="users", OPTIONS="last_rule"
KERNEL="dvb*", PROGRAM="/etc/udev/dvb.sh %k", NAME="%c", GROUP="users", OPTIONS="last_rule"
KERNEL="video[0-9]*", NAME="v4l/video%n", GROUP="users", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="radio[0-9]*", NAME="v4l/radio%n", GROUP="users", SYMLINK="radio%e", OPTIONS="last_rule"
KERNEL="vbi[0-9]*", NAME="v4l/vbi%n", GROUP="users", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="vtx[0-9]*", NAME="v4l/vtx%n", GROUP="users", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="controlC[0-9]*", NAME="snd/%k", OPTIONS="last_rule"
KERNEL="hw[CD0-9]*", NAME="snd/%k", OPTIONS="last_rule"
KERNEL="pcm[CD0-9cp]*", NAME="snd/%k", OPTIONS="last_rule"
KERNEL="midi[CD0-9]*", NAME="snd/%k", OPTIONS="last_rule"
KERNEL="timer", NAME="snd/%k", OPTIONS="last_rule"
KERNEL="seq", NAME="snd/%k", OPTIONS="last_rule"
KERNEL="audio*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="dmmidi*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="admmidi*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="dsp*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="adsp*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="midi*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="amidi*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="mixer*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="sequencer*", NAME="sound/%k", SYMLINK="%k", OPTIONS="last_rule"
KERNEL="pktcdvd", NAME="pktcdvd/control", GROUP="users", MODE="0660", OPTIONS="last_rule"
KERNEL="pktcdvd[0-9]*", NAME="pktcdvd/pktcdvd%n", GROUP="users", MODE="0660", OPTIONS="last_rule"
The problem with /dev/hdc was that first udev (version 057) was reading a rule from my 00 file (BUS="ide", KERNEL="hdc"...) with GROUP=users. Then it was reading SUBSYSTEM="block", GROUP="disk" rule from the basic file (but it wasn't executed at that time). And then it was reading BUS="ide", KERNEL="hd[a-z]", SYSFS{removable}="1"... with GROUP=optical. Then it was executing SUBSYTEM rule (hdc is a block device). That's why only disk group had an access to /dev/hdc (with OPTIONS="last_rule" in the basic file in the GROUP="optical" line it would ignore SUBSYSTEM rule).
There are also other rules that you should add (IMO) to your custom rules if  you are changing something. In my case it's for example BUS="ide", KERNEL="hd[a-z]", PROGRAM="/etc/udev/cdsymlinks.sh %k"... which creates symlinks for cd drives. This rule must be above other rules (the number of the symlinks is now unlimited - previously it was 5 IIRC).
So now the rules are mixed together in the lexical order (except SUBSYTEM rules which are executed at the end) unless OPTIONS="last_rule" is used or second (and other) rule has a NAME filed (only one rule for a given device can have NAME filed. Every other rule for the same device with NAME field is ignored IIRC). It also means you can now split rules for a device into several rules - only one of them can have NAME filed and the last should have OPTIONS="last_rule".
Since in your case you have custom rules only for a well defined usb devices (not /dev/sd*) IMO it should work as you think (only add OPTIONS="last_rule").
I hope it's now perfectly clear  8)