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