2 - Raspberry PI Community Projects

• $major or %M: the kernel major number of the device;
• $minor or %m: the kernel minor number of the device;
• $result or %c: the string output by the last program invoked by PROGRAM;
• and, finally, %% and $$ for the percent and dollar sign, respectively.
The above lists are not complete (they include only the most important parameters), but the
udev(7) manual page should be.
9.11.4. A concrete example
Let us consider the case of a simple USB key and try to assign it a fixed name. First, you must
find the elements that will identify it in a unique manner. For this, plug it in and run udevadm
info -a -n /dev/sdc (replacing /dev/sdc with the actual name assigned to the key).
# udevadm info -a -n /dev/sdc
[...]
looking at device '/devices/pci0000:00/0000:00:10.3/usb1
➥ /1-2/1-2.2/1-2.2:1.0/host9/target9:0:0/9:0:0:0/block/sdc':
[...]
KERNEL=="sdc"
SUBSYSTEM=="block"
DRIVER==""
ATTR{range}=="16"
ATTR{ext_range}=="256"
ATTR{removable}=="1"
ATTR{ro}=="0"
ATTR{size}=="126976"
ATTR{alignment_offset}=="0"
ATTR{capability}=="53"
ATTR{stat}==" 51 100 1208 256 0 0
➥ 0 0 0 192 25 6"
ATTR{inflight}==" 0 0"
looking at parent device '/devices/pci0000:00/0000:00:10.3/usb1
➥ /1-2/1-2.2/1-2.2:1.0/host9/target9:0:0/9:0:0:0':
KERNELS=="9:0:0:0"
SUBSYSTEMS=="scsi"
DRIVERS=="sd"
ATTRS{device_blocked}=="0"
ATTRS{type}=="0"
ATTRS{scsi_level}=="3"
ATTRS{vendor}=="I0MEGA "
ATTRS{model}=="UMni64MB*IOM2C4 "
216 The Debian Administrator's Handbook