1 Boot time creation of mapped devices
2 ===================================
4 It is possible to configure a device mapper device to act as the root
5 device for your system in two ways.
7 The first is to build an initial ramdisk which boots to a minimal
8 userspace which configures the device, then pivot_root(8) in to it.
10 For simple device mapper configurations, it is possible to boot directly
11 using the following kernel command line:
13 dm="<name> <uuid> <ro>,table line 1,...,table line n"
15 name = the name to associate with the device
16 after boot, udev, if used, will use that name to label
18 uuid = may be 'none' or the UUID desired for the device.
19 ro = may be "ro" or "rw". If "ro", the device and device table will be
22 Each table line may be as normal when using the dmsetup tool except for
24 1. Any use of commas will be interpreted as a newline
25 2. Quotation marks cannot be escaped and cannot be used without
26 terminating the dm= argument.
28 Unless renamed by udev, the device node created will be dm-0 as the
29 first minor number for the device-mapper is used during early creation.
34 - Booting to a linear array made up of user-mode linux block devices:
36 dm="lroot none 0, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" \
39 Will boot to a rw dm-linear target of 8192 sectors split across two
40 block devices identified by their major:minor numbers. After boot, udev
41 will rename this target to /dev/mapper/lroot (depending on the rules).