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Diffstat (limited to 'doc/usage')
| -rw-r--r-- | doc/usage/index.rst | 1 | ||||
| -rw-r--r-- | doc/usage/mbr.rst | 94 |
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diff --git a/doc/usage/index.rst b/doc/usage/index.rst index ada0df08c0..6def250766 100644 --- a/doc/usage/index.rst +++ b/doc/usage/index.rst @@ -17,4 +17,5 @@ Shell commands bootefi bootmenu button + mbr pstore diff --git a/doc/usage/mbr.rst b/doc/usage/mbr.rst new file mode 100644 index 0000000000..bddf2f612a --- /dev/null +++ b/doc/usage/mbr.rst @@ -0,0 +1,94 @@ +.. SPDX-License-Identifier: GPL-2.0+ + +mbr command +=========== + +Synopsis +-------- + +:: + + mbr verify [interface] [device no] [partition list] + mbr write [interface] [device no] [partition list] + +Description +----------- + +The mbr command lets users create or verify the MBR (Master Boot Record) +partition layout based on the provided text description. The partition +layout is alternatively read from the 'mbr_parts' environment variable. +This can be used in scripts to help system image flashing tools to ensure +proper partition layout. + +The syntax of the text description of the partition list is similar to +the one used by the 'gpt' command. + +Supported partition parameters are: + +* name (currently ignored) +* start (partition start offset in bytes) +* size (in bytes or '-' to expand it to the whole free area) +* bootable (boolean flag) +* id (MBR partition type) + +If one wants to create more than 4 partitions, an 'Extended' primary +partition (with 0x05 ID) has to be explicitly provided as a one of the +first 4 entries. + +Here is an example how to create a 6 partitions (3 on the 'extended +volume'), some of the predefined sizes: + +:: + + => setenv mbr_parts 'name=boot,start=4M,size=128M,bootable,id=0x0e; + name=rootfs,size=3072M,id=0x83; + name=system-data,size=512M,id=0x83; + name=[ext],size=-,id=0x05; + name=user,size=-,id=0x83; + name=modules,size=100M,id=0x83; + name=ramdisk,size=8M,id=0x83' + => mbr write mmc 0 + +To check if the layout on the MMC #0 storage device matches the provided +text description one has to issue following command (assuming that +mbr_parts environment variable is set): + +:: + + => mbr verify mmc 0 + +The verify sub-command is especially useful in the system update scripts: + +:: + + => if mbr verify mmc 0; then + echo MBR layout needs to be updated + ... + fi + +The 'mbr write' command returns 0 on success write or 1 on failure. + +The 'mbr verify' returns 0 if the layout matches the one on the storage +device or 1 if not. + +Configuration +------------- + +To use the mbr command you must specify CONFIG_CMD_MBR=y. + +Return value +------------ + +The variable *$?* takes the following values + ++---+------------------------------+ +| 0 | mbr write was succesful | ++---+------------------------------+ +| 1 | mbr write failed | ++---+------------------------------+ +| 0 | mbr verify was succesful | ++---+------------------------------+ +| 1 | mbr verify was not succesful | ++---+------------------------------+ +|-1 | invalid arguments | ++---+------------------------------+ |