Linux: devices (block, character), udev

Немного теории.

udev - это демон, который отвечает за виртуальную файловую систему /dev.
/etc/udev/ - каталог настроек демона.
/etc/udev/rules.d/ - каталог с правилами, по которым udev создаёт файлы устройств в /dev.
70-persistent-net.rules - правило для создания сетевых интерфейсов.

Device Files

Each piece of hardware in the system has an associated file used by the kernel to communicate with it. This type of file is called a device file. There are two types of device files: a character (or raw) device file and a block device file.
The first character in each line entry tells if the file type is block or character. Ab denotes a block device file and a c represents a character device file.

[root@host1 ~]# ll /dev/sd*
brw-rw----. 1 root disk 8, 0 Aug 4 14:13 /dev/sda
brw-rw----. 1 root disk 8, 1 Aug 4 14:13 /dev/sda1
brw-rw----. 1 root disk 8, 2 Aug 4 14:13 /dev/sda2

[root@host1 ~]# ll /dev/usb*
crw-------. 1 root root 250, 0 Aug 4 14:13 /dev/usbmon0
crw-------. 1 root root 250, 1 Aug 4 14:13 /dev/usbmon1
crw-------. 1 root root 250, 2 Aug 4 14:13 /dev/usbmon2

[root@host1 ~]# file /dev/sda
/dev/sda: block special

[root@host1 ~]# file /dev/usbmon0
/dev/usbmon0: character special