RHCE - Part 1

Filesystem Device Nodes

• In Linux, most most devices accesed as a file.
• 2 types of devices: Character and Block devices
  brw-rw---- 1 root floppy 2, 2 Apr 11 10:25 /dev/fd0
  crw-rw---- 1 root uucp 4, 64 Apr 11 10:25 /dev/ttyS0
  • Block devices: random access devices (storage...)
    • hd[a-t]
    • sd[a-z]+
    • fd[0-7]
    • md[0-31]
    • loop[0-15]
    • ram[0-19]
  • Character devices: streams of data (comm ports...)
    • tty[0-31] virtual consoles
    • ttyS[0-9]+ serial ports
    • lp[0-3]
    • null 'blackhole'
    • zero 'infinite'
    • [u]random 'source of randomness'
    • fb[0-31] framebuffer devices
  • Symbolic links : /dev/cdrom --> /dev/hdd
  • ls -l reveals type (first character)
  • Devices have ownership (3D games, modem access)
  • Each node has a Major and a Minor number
    • Major number: indexes a particular DD in the Kernel
    • Minor number: device driver parameter
• They are in /dev by convention (can be anywhere)
• Create a device with /bin/mknod
  

  mknod cdrom b 22 64