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Diffstat (limited to 'docs/gnulinux/grub_cbfs.html')
| -rw-r--r-- | docs/gnulinux/grub_cbfs.html | 58 |
1 files changed, 57 insertions, 1 deletions
diff --git a/docs/gnulinux/grub_cbfs.html b/docs/gnulinux/grub_cbfs.html index 5fb46dc..1cbc886 100644 --- a/docs/gnulinux/grub_cbfs.html +++ b/docs/gnulinux/grub_cbfs.html @@ -33,6 +33,11 @@ such that the 'grub.cfg' and 'grubtest.cfg' files exists directly inside CBFS instead of inside the GRUB payload 'memdisk' (which is itself stored in CBFS). </p> + <p> + You can either modify + the GRUB configuration stored in the flash chip, or you can modify a GRUB configuration + file on the main storage which the libreboot GRUB payload will automatically search for. + </p> <p> Here is an excellent writeup about CBFS (coreboot filesystem): @@ -45,6 +50,7 @@ <ul> <li><a href="#getting_started">Getting started</a></li> + <li><a href="#libreboot_grub_config_ondisk">Don't want to flash a new ROM image?</a></li> <li><a href="#build_cbfstool">Build 'cbfstool' from source</a></li> <li><a href="#which_rom">Which ROM image should I use?</a></li> <li><a href="#extract_grubtest">Extract grubtest from the ROM image</a> @@ -81,6 +87,56 @@ </p> <hr/> + + <h2 id="libreboot_grub_config_ondisk">Don't want to flash a new ROM image?</h2> + + <p> + There are several advantages to modifying the GRUB configuration stored in CBFS, but + this also means that you have to flash a new libreboot ROM image on your machine (some users + feel intimidated by this, to say the least). + Doing so can be risky if not handled correctly, because it can result in a bricked + machine (recovery is easy if you have the <a href="../install/bbb_setup.html">equipment</a> + for it, but most people don't). If you aren't up to that then don't worry; it is possible + to use a custom GRUB menu without flashing a new image, by loading a GRUB configuration + from a partition on the main storage instead. + </p> + + <p> + By default, GRUB in libreboot is configured to scan all partitions on the main storage + for /boot/grub/libreboot_grub.cfg or /grub/libreboot_grub.cfg(for systems where /boot + is on a dedicated partition), and then use it automatically. + </p> + <p> + Simply create your custom GRUB configuration and save it to <b>/boot/grub/libreboot_grub.cfg</b> + on the running system. The next time you boot, GRUB (in libreboot) will automatically switch to + this configuration file. <b>This means that you do not have to re-flash, recompile or otherwise + modify libreboot at all!</b> + </p> + + <p> + Ideally, your distribution should automatically generate a libreboot_grub.cfg file that is written + specifically under the assumption that it will be read and used on a libreboot system that uses + GRUB as a payload. If your distribution does not do this, then you can try to add that feature + yourself or politely ask someone involved with or otherwise knowledgeable about the distribution + to do it for you. The libreboot_grub.cfg could either contain the full configuration, or it could + chainload another GRUB ELF executable (built to be used as a coreboot payload) that is located in + a partition on the main storage. + </p> + + <p> + If you want to adapt a copy of the existing <i>libreboot</i> GRUB configuration and use that for the libreboot_grub.cfg file, then + follow <a href="#build_cbfstool">#build_cbfstool</a>, <a href="#which_rom">#which_rom</a> and + <a href="#extract_grubtest">#extract_grubtest</a> to get the <b><i>grubtest.cfg</i></b>. + Rename <b><i>grubtest.cfg</i></b> to <b><i>libreboot_grub.cfg</i></b> and save it to <b><i>/boot/grub/</i></b> + on the running system where it is intended to be used. Modify the file at that location however you see fit, + and then stop reading this guide (the rest of this page is irrelevant to you). + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> <h2 id="build_cbfstool">Build 'cbfstool' from source</h2> @@ -103,7 +159,7 @@ <p> You can work directly with one of the ROM images already included in the libreboot ROM archives. For the purpose of - this tutorial it is assumed that your ROM is named <i>libreboot.rom</i> so please make sure to adapt. + this tutorial it is assumed that your ROM image file is named <i>libreboot.rom</i>, so please make sure to adapt. </p> <p> |