next up previous contents
Next: 2.2.4.0.3 Other paramers Up: 2.2.4 Specifying boot time Previous: 2.2.4.0.1 How the kernel   Contents

2.2.4.0.2 The `root=' Argument

This argument tells the kernel what device is to be used as the root filesystem while booting. The default of this setting is the value of the root device of the system that the kernel was built on or the parameters set during the installation in lilo.conf or grub.conf. For example, if the lilo.conf has `root=/dev/hda1' in the stanza for that image, then the default root device would be `/dev/hda1'. To override this default value, and select the first partition on the second hard drive as the root device, one would use `root=/dev/hdb1'.

Valid root devices are any of the following devices:

  1. /dev/hdaN to /dev/hddN, which is partition N on ST-506 compatible disk `a to d'.
  2. /dev/sdaN to /dev/sdeN, which is partition N on SCSI compatible disk `a to e'.
  3. /dev/xdaN to /dev/xdbN, which is partition N on XT compatible disk `a to b'.
  4. /dev/fdN, which is floppy disk drive number N. Having N=0 would be the DOS `A:' drive, and N=1 would be `B:'.
  5. /dev/nfs, which is not really a device, but rather a flag to tell the kernel to get the root fs via the network.
  6. /dev/ram, which is the RAM disk.
The more awkward and less portable numeric specification of possible disk devices in major/minor format is also accepted. So, for example /dev/sda1 is major 8, minor 1, so you could use root=0x801 as an alternative.

next up previous contents
Next: 2.2.4.0.3 Other paramers Up: 2.2.4 Specifying boot time Previous: 2.2.4.0.1 How the kernel   Contents