[8.04] /dev/null permissions change

**martinix** · July 3rd, 2008

Hi there,

I'm having this problem a few days now and I'm having a hard time looking in the right places:
Opening a terminal I get a lot of lines saying
bash /dev/null permission denied

Code:

ls- l /dev/null

gives

Code:

crw------- 1 root root 1, 3 2008-05-09 11:05 /dev/null

I've been looking on the web and over here and found many solutions like

Code:

sudo chown 666 /dev/null

and

Code:

chmod a+rw /dev/null

and

Code:

sudo rm /dev/null
sudo mknod -m 666 /dev/null c 1 3
sudo chown root:root /dev/null

resulting in:

Code:

crw-rw-rw- 1 root root 1, 3 2008-07-03 09:59 /dev/null

which works until the next reboot.

Following the line of this thread: http://ubuntuforums.org/showthread.p...mission+denied

I get:

Code:

grep root /etc/udev/rules.d/*

Code:

/etc/udev/rules.d/40-permissions.rules:# device on the bus and those devices may do anything as root on your system.
/etc/udev/rules.d/80-programs.rules:    RUN+="create_floppy_devices -c -t $attr{cmos} -m %M -M 0640 -G disk $root/%k"

and:

Code:

grep null /etc/udev/rules.d/*

Code:

/etc/udev/rules.d/40-basic-permissions.rules:KERNEL=="null",                            MODE="0666"

How do I find out what's causing this?
Does it have anything to to with the floppy device?
Which log tells me more?

Help is very much appreciated.

**justleen** · July 3rd, 2008

weird.. in the link you give, they grep for "terminator" not "root". so the first output you can ignore.
the grep on "null" apears correct.

this bit:
sudo rm /dev/null
sudo mknod -m 666 /dev/null c 1 3
sudo chown root:root /dev/null

should fix things...

can you find anything in your /var/log/udev? empty it, then reboot, see what you find on /dev/null in there?

**cafemartin** · July 3rd, 2008

It seems he renamed his root account to terminator or so.
I apllied the grep resulting in

Code:

/etc/udev/rules.d/40-permissions.rules:# device on the bus and those devices may do anything as root on your system.
/etc/udev/rules.d/80-programs.rules:    RUN+="create_floppy_devices -c -t $attr{cmos} -m %M -M 0640 -G disk $root/%k"

with root.

The grep null looks similar to what I've seen in other threads.
The grep root does not.

Code:

sudo rm /dev/null
sudo mknod -m 666 /dev/null c 1 3
sudo chown root:root /dev/null

Only helps until the reboot, thereafter it all starts over again.

Weird thing is, I don't seem to have a /var/log/udev
where else might it reside?

**martinix** · July 3rd, 2008

Ok, that was silly: I found /var/log/udev.

I emptied it, but this did not help.

when /var/log/udev fills again, the only mentioning of /dev/null i find to be:

UDEV [1215091088.577371] add /devices/virtual/mem/null (mem)
UDEV_LOG=3
ACTION=add
DEVPATH=/devices/virtual/mem/null
SUBSYSTEM=mem
MAJOR=1
MINOR=3
SEQNUM=1957
UDEVD_EVENT=1
DEVNAME=/dev/null

In this link there's also a similar, although perhaps different problem. https://bugs.launchpad.net/ubuntu/+s...ev/+bug/149346

If I do the mentioned ls commands,

Code:

ls /etc/rcS.d | grep udev

I get:

Code:

S10udev
S37udev-finish

and on

Code:

ls /etc/rc2.d | grep udev

I get:

Code:

S50udev
S50udev-finish

no idea if it's good or bad.

**martinix** · July 3rd, 2008

grasping in the dark, latest update:

reading some files in /etc/udev/rules.d

In /etc/udev/rules.d/40-permissions.rules (which is the file that to me beginner seems most relevant),

I find:

Code:

# Block devices
SUBSYSTEM!="block", GOTO="block_end"
ATTRS{removable}!="1",                  GROUP="disk"
ATTRS{removable}=="1",                  GROUP="floppy"
SUBSYSTEMS=="usb",                      GROUP="plugdev"
SUBSYSTEMS=="ieee1394",                 GROUP="plugdev"
SUBSYSTEMS=="mmc",                      GROUP="plugdev"
SUBSYSTEMS=="pcmcia",                   GROUP="plugdev"
LABEL="block_end"

# IDE devices
ENV{ID_CDROM}=="?*",                    GROUP="cdrom"
KERNEL=="ht[0-9]*",                     GROUP="tape"
KERNEL=="nht[0-9]*",                    GROUP="tape"

# IEEE1394 (firewire) devices
# Please note that raw1394 gives unrestricted, raw access to every single
# device on the bus and those devices may do anything as root on your system.
# Yes, I know it also happens to be the only way to rewind your video camera,
# but it's not going to be group "video", okay?
KERNEL=="raw1394",                      GROUP="disk"
KERNEL=="dv1394*",                      GROUP="video"
KERNEL=="video1394*",                   GROUP="video"

# Packet CD devices, group under /dev/pktcdvd
KERNEL=="pktcdvd",                      MODE="0644"
KERNEL=="pktcdvd[0-9]*",                GROUP="cdrom"

# Printers and Parallel devices
SUBSYSTEM=="printer",                   GROUP="lp"
SUBSYSTEM=="ppdev",                     GROUP="lp"
SUBSYSTEM=="usb", KERNEL=="lp[0-9]*",   GROUP="lp"
KERNEL=="pt[0-9]*",                     GROUP="tape"
KERNEL=="pht[0-9]*",                    GROUP="tape"

# SCSI devices
SUBSYSTEMS=="scsi", GOTO="scsi_start"
GOTO="scsi_end"
LABEL="scsi_start"
ATTRS{type}=="0",                       GROUP="disk"
ATTRS{type}=="1",                       GROUP="tape"
ATTRS{type}=="4",                       GROUP="cdrom"
ATTRS{type}=="5",                       GROUP="cdrom"
ATTRS{type}=="6",                       GROUP="scanner"
ATTRS{type}=="8",                       GROUP="tape"
ATTRS{type}=="3", ATTRS{vendor}=="HP",  GROUP="scanner"
ATTRS{type}=="3", ATTRS{vendor}=="Epson", GROUP="scanner"
ATTRS{type}=="3", ATTRS{vendor}=="EPSON", GROUP="scanner"
LABEL="scsi_end"

# Serial devices
SUBSYSTEM=="tty",                       GROUP="dialout"
SUBSYSTEM=="capi",                      GROUP="dialout"
SUBSYSTEM=="slamr",                     GROUP="dialout"
SUBSYSTEM=="zaptel",                    GROUP="dialout"
KERNEL=="ttyLTM[0-9]*",                 GROUP="dialout", MODE="0660"

# USB serial converters
SUBSYSTEM=="usb_device", GOTO="usb_serial_start"
SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", GOTO="usb_serial_start"
GOTO="usb_serial_end"
LABEL="usb_serial_start"
ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", \
                                        MODE="0660", GROUP="dialout"
LABEL="usb_serial_end"

# Sound devices
SUBSYSTEM=="sound",                     GROUP="audio"

# pty devices
SUBSYSTEM=="tty", KERNEL=="pty*",       GROUP="tty", MODE="0666"

# Video devices
SUBSYSTEM=="drm",                       GROUP="video"
SUBSYSTEM=="dvb",                       GROUP="video"
SUBSYSTEM=="graphics",                  GROUP="video"
SUBSYSTEM=="video4linux",               GROUP="video"
KERNEL=="agpgart",                      GROUP="video"
KERNEL=="nvidia*",                      GROUP="video"
SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", GOTO="usb_serial_start"
GOTO="usb_serial_end"
LABEL="usb_serial_start"
ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", \
                                        MODE="0660", GROUP="dialout"
LABEL="usb_serial_end"

# Sound devices
SUBSYSTEM=="sound",                     GROUP="audio"

# pty devices
SUBSYSTEM=="tty", KERNEL=="pty*",       GROUP="tty", MODE="0666"

# Video devices
SUBSYSTEM=="drm",                       GROUP="video"
SUBSYSTEM=="dvb",                       GROUP="video"
SUBSYSTEM=="graphics",                  GROUP="video"
SUBSYSTEM=="video4linux",               GROUP="video"
KERNEL=="agpgart",                      GROUP="video"
KERNEL=="nvidia*",                      GROUP="video"

# Other devices, by name
KERNEL=="mem",                          GROUP="kmem", MODE="0640"
KERNEL=="kmem",                         GROUP="kmem", MODE="0640"
KERNEL=="port",                         GROUP="kmem", MODE="0640"
KERNEL=="nvram",                        GROUP="nvram"
KERNEL=="rtc",                          GROUP="audio"
KERNEL=="js[0-9]*",                     GROUP="plugdev"

Since "mem" was the only mentioning I found in /var/log/udev, perhaps something is wrong with

Code:

KERNEL=="mem",                          GROUP="kmem", MODE="0640"

?

I find in /etc/udev/rules.d/80-programs.rules

Code:

# Load firmware on demand
SUBSYSTEM=="firmware", ACTION=="add", RUN+="firmware_helper"

# Create special nodes for floppy devices
KERNEL=="fd[0-9]*", ACTION=="add", ATTRS{cmos}=="?*", \
        RUN+="create_floppy_devices -c -t $attr{cmos} -m %M -M 0640 -G disk $root/%k"

which was the second remark outputted by

Code: