diff options
author | Masami Hiramatsu <mhiramat@kernel.org> | 2022-03-13 17:08:25 +0900 |
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committer | Masami Hiramatsu <mhiramat@kernel.org> | 2022-04-06 10:07:32 +0900 |
commit | 37e22d3013b3e23353bfaf16159388f7066704a8 (patch) | |
tree | bd7b1cc8be6c619d4bcf38c4acd1a707469e7bf5 | |
parent | 801126678c74c59f578d52f12f9c1aa17d4e7a8e (diff) | |
download | linux-bootconfig/core.tar.gz |
docs: bootconfig: Add how to embed the bootconfig into kernelbootconfig/core
Add a description how to embed the bootconfig file into kernel.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v7:
- Rename CONFIG_EMBED_BOOT_CONFIG* to CONFIG_BOOT_CONFIG_EMBED*.
Changes in v5:
- Update CONFIG_EMBED_BOOT_CONFIG_FILE which can accept relative path.
Changes in v3:
- Fix typos.
Changes in v2:
- Corrected the text accoding to Randy's suggestion.
- Do not reccomend to use relative path for CONFIG_EMBED_BOOT_CONFIG_FILE.
-rw-r--r-- | Documentation/admin-guide/bootconfig.rst | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index a1860fc0ca88a..d99994345d41d 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -158,9 +158,15 @@ Each key-value pair is shown in each line with following style:: Boot Kernel With a Boot Config ============================== -Since the boot configuration file is loaded with initrd, it will be added -to the end of the initrd (initramfs) image file with padding, size, -checksum and 12-byte magic word as below. +There are two options to boot the kernel with bootconfig: attaching the +bootconfig to the initrd image or embedding it in the kernel itself. + +Attaching a Boot Config to Initrd +--------------------------------- + +Since the boot configuration file is loaded with initrd by default, +it will be added to the end of the initrd (initramfs) image file with +padding, size, checksum and 12-byte magic word as below. [initrd][bootconfig][padding][size(le32)][checksum(le32)][#BOOTCONFIG\n] @@ -196,6 +202,25 @@ To remove the config from the image, you can use -d option as below:: Then add "bootconfig" on the normal kernel command line to tell the kernel to look for the bootconfig at the end of the initrd file. +Embedding a Boot Config into Kernel +----------------------------------- + +If you can not use initrd, you can also embed the bootconfig file in the +kernel by Kconfig options. In this case, you need to recompile the kernel +with the following configs:: + + CONFIG_BOOT_CONFIG_EMBED=y + CONFIG_BOOT_CONFIG_EMBED_FILE="/PATH/TO/BOOTCONFIG/FILE" + +``CONFIG_BOOT_CONFIG_EMBED_FILE`` requires an absolute path or a relative +path to the bootconfig file from source tree or object tree. +The kernel will embed it as the default bootconfig. + +Just as when attaching the bootconfig to the initrd, you need ``bootconfig`` +option on the kernel command line to enable the embedded bootconfig. + +Note that even if you set this option, you can override the embedded +bootconfig by another bootconfig which attached to the initrd. Kernel parameters via Boot Config ================================= |