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Diffstat (limited to 'Documentation/device-mapper/boot.txt')
| -rw-r--r-- | Documentation/device-mapper/boot.txt | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/Documentation/device-mapper/boot.txt b/Documentation/device-mapper/boot.txt new file mode 100644 index 000000000000..adcaad5e5e32 --- /dev/null +++ b/Documentation/device-mapper/boot.txt @@ -0,0 +1,42 @@ +Boot time creation of mapped devices +=================================== + +It is possible to configure a device mapper device to act as the root +device for your system in two ways. + +The first is to build an initial ramdisk which boots to a minimal +userspace which configures the device, then pivot_root(8) in to it. + +For simple device mapper configurations, it is possible to boot directly +using the following kernel command line: + +dm="<name> <uuid> <ro>,table line 1,...,table line n" + +name = the name to associate with the device + after boot, udev, if used, will use that name to label + the device node. +uuid = may be 'none' or the UUID desired for the device. +ro = may be "ro" or "rw". If "ro", the device and device table will be + marked read-only. + +Each table line may be as normal when using the dmsetup tool except for +two variations: +1. Any use of commas will be interpreted as a newline +2. Quotation marks cannot be escaped and cannot be used without + terminating the dm= argument. + +Unless renamed by udev, the device node created will be dm-0 as the +first minor number for the device-mapper is used during early creation. + +Example +======= + +- Booting to a linear array made up of user-mode linux block devices: + + dm="lroot none 0, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" \ + root=/dev/dm-0 + +Will boot to a rw dm-linear target of 8192 sectors split across two +block devices identified by their major:minor numbers. After boot, udev +will rename this target to /dev/mapper/lroot (depending on the rules). +No uuid was assigned. |