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diff --git a/docs/gnulinux/grub_cbfs.html b/docs/gnulinux/grub_cbfs.html new file mode 100644 index 0000000..c9a0f45 --- /dev/null +++ b/docs/gnulinux/grub_cbfs.html @@ -0,0 +1,400 @@ +<!DOCTYPE html> +<html> +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1"> + + <style type="text/css"> + @import url('../css/main.css'); + </style> + + <title>Libreboot documentation: GRUB menu</title> +</head> + +<body> + <header> + <h1 id="pagetop">How to change your default GRUB menu</h1> + <aside>Or <a href="index.html">back to main index</a></aside> + </header> + + <p> + Libreboot uses the GRUB <a href="http://www.coreboot.org/Payloads#GRUB_2">payload</a> + by default, which means that the GRUB configuration file + (where your GRUB menu comes from) is stored directly alongside libreboot + and it's GRUB payload executable, inside + the flash chip. In context, this means that installing distributions and managing them + is handled slightly differently compared to traditional BIOS systems. + </p> + + <p> + A libreboot (or coreboot) ROM image is not simply "flat"; there is an actual + filesystem inside called CBFS (coreboot filesystem). A utility called 'cbfstool' + allows you to change the contents of the ROM image. In this case, libreboot is configured + such that the 'grub.cfg' and 'grubtest.cfg' files exists directly inside CBFS instead of + inside the GRUB payload's 'memdisk' (which is itself stored in CBFS). + </p> + + <p> + Here is an excellent writeup about CBFS (coreboot filesystem): + <a href="http://lennartb.home.xs4all.nl/coreboot/col5.html">http://lennartb.home.xs4all.nl/coreboot/col5.html</a>. + </p> + +<hr/> + + <h2>Table of Contents</h2> + + <ul> + <li><a href="#getting_started">Getting started</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> + <li> + <a href="#example_modifications">Example modifications for <i>grubtest.cfg</i></a> + <ul> + <li><a href="#example_modifications_trisquel">Trisquel GNU/Linux-libre</a></li> + <li><a href="#example_modifications_parabola">Parabola GNU/Linux-libre</a></li> + </ul> + </li> + <li><a href="#reinsert_modified_grubtest">Re-insert the modified grubtest.cfg into the ROM image</a></li> + <li><a href="#test_it">Test it!</a> + <li><a href="#final_steps">Final steps</a></li> + <li><a href="#troubleshooting">Troubleshooting</a></li> + </ul> + +<hr/> + + <h2 id="getting_started">Getting started</h2> + + <p> + Download the latest release from + <a href="http://libreboot.org/">http://libreboot.org/</a> + <br/><b>If you downloaded from git, refer to + <a href="../git/index.html#build_meta">../git/index.html#build_meta</a> before continuing.</b> + </p> + + <p> + <a href="../git/index.html#build_dependencies">Install the build dependencies</a>. + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <h2 id="build_cbfstool">Build 'cbfstool' from source</h2> + + <p> + If you are working with libreboot_src, then you can run <b><i>make</i></b> command in + libreboot_src/coreboot/util/cbfstool to build the <b><i>cbfstool</i></b> and <b><i>rmodtool</i></b> + executable. + </p> + <p> + Alternatively if you are working with libreboot_bin, then you can run <b><i>./builddeps-cbfstool</i></b> + command inside libreboot_bin/; a <b><i>cbfstool</i></b> and <b><i>rmodtool</i></b> + executable will appear under libreboot_bin/ + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <h2 id="which_rom">Which ROM image should I use?</h2> + + <p> + You can work directly with one of the ROM's 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. + </p> + + <p> + If you want to re-use the ROM that you currently have flashed (and running) then see + <a href="../git/index.html#build_flashrom">../git/index.html#build_flashrom</a> + and then run:<br/> + <b>$ sudo ./flashrom -p internal -r libreboot.rom</b><br/> + Notice that this is using <b>"-r"</b> (read) instead of <b>"-w"</b> (write). + This will create a dump (copy) of your current firmware and name it <b>libreboot.rom</b>. + You need to take ownership of the file. For example:<br/> + <b>$ sudo chown yourusername:yourusername libreboot.rom</b><br/> + <b># chown yourusername:yourusername libreboot.rom</b> + </p> + + <p> + If you currently have flashed a ROM image from an older version, it is recommended to update first: + basically, modify one of the latest ROM's and then flash it. + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <h2 id="extract_grubtest">Extract grubtest.cfg from the ROM image</h2> + + <p> + Display contents of ROM:<br/> + <b>$ ./cbfstool libreboot.rom print</b> + </p> + + <p> + The libreboot.rom file contains your <i>grub.cfg</i> and <i>grubtest.cfg</i> files. + You should extract, modify and re-insert the copy first. grub.cfg will load first, + but it has a menu entry for switching to the copy (grubtest.cfg). + This reduces your chance of making a mistake that could make your machine unbootable (or very hard to boot). + </p> + + <p> + Extract grubtest.cfg from the ROM image:<br/> + <b>$ ./cbfstool libreboot.rom extract -n grubtest.cfg -f grubtest.cfg</b> + </p> + + <p> + Now you have a grubtest.cfg in cbfstool directory. Edit it however you wish. + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <div class="important"> + + <h2 id="example_modifications">Example modifications for <i>grubtest.cfg</i></h2> + + <p> + These are some common examples of ways in which the grubtest.cfg file can be modified. + </p> + + <h3 id="example_modifications_trisquel">Trisquel GNU/Linux-libre</h3> + + <p> + As an example, on my test system in /boot/grub/grub.cfg (on the HDD/SSD) I see for the main menu entry: + </p> + <ul> + <li><b>linux /boot/vmlinuz-3.15.1-gnu.nonpae root=UUID=3a008e14-4871-497b-95e5-fb180f277951 ro crashkernel=384M-2G:64M,2G-:128M quiet splash $vt_handoff</b></li> + <li><b>initrd /boot/initrd.img-3.15.1-gnu.nonpae</b></li> + </ul> + + <p> + <b>ro</b>, <b>quiet</b>, <b>splash</b>, <b>crashkernel=384M-2G:64M,2G-:128M</b> and + <b>$vt_handoff</b> can be safely ignored. + </p> + + <p> + I use this to get my partition layout:<br/> + $ <b>lsblk</b> + </p> + + <p> + In my case, I have no /boot partition, instead /boot is on the same partition as / on sda1. + Yours might be different. In GRUB terms, sda means ahci0. 1 means msdos1, or gpt1, depending + on whether I am using MBR or GPT partitioning. Thus, /dev/sda1 is GRUB is (ahci0,msdos1) or + (ahci0,gpt1). In my case, I use MBR partitioning so it's (ahci0,msdos1). + 'msdos' is GRUB's name simply because this partitioning type is traditionally used by MS-DOS. + It doesn't mean you have a proprietary OS. + </p> + + <p> + Trisquel doesn't keep the filenames of kernels consistent, instead it keeps old kernels and + new kernel updates are provided with the version in the filename. This can make GRUB payload + a bit tricky. Fortunately, there are symlinks /vmlinuz and /initrd.img + so if your /boot and / are on the same partition, you can set GRUB to boot from that. + These are also updated automatically when installing kernel updates from your distributions + apt-get repositories. + <b> + Note: when using <a href="http://jxself.org/linux-libre">jxself kernel releases</a>, + these are not updated at all and you have to update them manually. + </b> + </p> + + <p> + For the GRUB payload's grubtest.cfg (in the 'Load Operating System' menu entry), we therefore have (in this example):<br/> + <b>set root='ahci0,msdos1'</b><br/> + <b>linux /vmlinuz root=UUID=3a008e14-4871-497b-95e5-fb180f277951</b><br/> + <b>initrd /initrd.img</b> + </p> + + <p> + Optionally, you can convert the UUID to it's real device name, for example /dev/sda1 in this case. + sdX naming isn't very reliable, though, which is why UUID is used for most distributions. + </p> + + <p> + Alternatively, if your /boot is on a separate partition then you cannot rely on the /vmlinuz and /initrd.img symlinks. + Instead, go into /boot and create your own symlinks (update them manually when you install a new kernel update).<br/> + $ <b>sudo -s</b><br/> + # <b>cd /boot/</b><br/> + # <b>rm -rf vmlinuz initrd.img</b><br/> + # <b>ln -s <u>kernel</u> ksym</b><br/> + # <b>ln -s <u>initrd</u> isym</b><br/> + # <b>exit</b> + </p> + + <p> + Replace the underlined <b>kernel</b> and <b>initrd</b> filenames above with the actual filenames, of course. + </p> + + <p> + Then your grubtest.cfg menu entry (for payload) becomes like that, for example if / was on sda2 and /boot was on sda1:<br/> + <b>set root='ahci0,msdos1'</b><br/> + <b>linux /ksym root=/dev/sda2</b><br/> + <b>initrd /isym</b> + </p> + + <p> + There are lots of possible variations so please try to adapt. + </p> + + <h3 id="example_modifications_parabola">Parabola GNU/Linux-libre</h3> + + <p> + You can basically adapt the above. Note however that Parabola does not keep old kernels still installed, and the file names + are always consistent, so you don't need to boot from symlinks, you can just use the real thing directly. + </p> + + </div> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <h2 id="reinsert_modified_grubtest">Re-insert the modified grubtest.cfg into the ROM image</h2> + + <p> + Delete the grubtest.cfg that remained inside the ROM:<br/> + <b>$ ./cbfstool libreboot.rom remove -n grubtest.cfg</b> + </p> + + <p> + Display ROM contents and now you see grubtest.cfg no longer exists there:<br/> + <b>$ ./cbfstool libreboot.rom print</b> + </p> + + <p> + Add the modified version that you just made:<br/> + <b>$ ./cbfstool libreboot.rom add -n grubtest.cfg -f grubtest.cfg -t raw</b> + </p> + + <p> + Now display ROM contents again and see that it exists again:<br/> + <b>$ ./cbfstool libreboot.rom print</b> + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <h2 id="test_it">Test it!</h2> + + <p> + <b> + Now you have a modified ROM. Refer back to <a href="../install/index.html#flashrom">../install/index.html#flashrom</a> for information + on how to flash it. Once you have done that, shut down and then boot up with your new test configuration. + </b> + </p> + + <p> + Choose (in GRUB) the menu entry that switches to grubtest.cfg. If it works, then your config is safe and you can continue below. + </p> + + <p> + <b> + If it does not work like you want it to, if you are unsure or sceptical in any way, + then re-do the steps above until you get it right! Do *not* proceed past this point + unless you are 100% sure that your new configuration is safe (or desirable) to use. + </b> + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <h2 id="final_steps">Final steps</h2> + + <p> + Create a copy of grubtest.cfg, called grub.cfg, which is the same except for one difference: + change the menuentry 'Switch to grub.cfg' to 'Switch to grubtest.cfg' and inside it, + change all instances of grub.cfg to grubtest.cfg. This is so that the main config still + links (in the menu) to grubtest.cfg, so that you don't have to manually switch to it, in + case you ever want to follow this guide again in the future (modifying the already modified config)<br/> + $ <b>sed -e 's:(cbfsdisk)/grub.cfg:(cbfsdisk)/grubtest.cfg:g' -e 's:Switch to grub.cfg:Switch to grubtest.cfg:g' < grubtest.cfg > grub.cfg</b><br/> + </p> + + <p> + Delete the grub.cfg that remained inside the ROM:<br/> + <b>$ ./cbfstool libreboot.rom remove -n grub.cfg</b> + </p> + + <p> + Display ROM contents and now you see grub.cfg no longer exists there:<br/> + <b>$ ./cbfstool libreboot.rom print</b> + </p> + + <p> + Add the modified version that you just made:<br/> + <b>$ ./cbfstool libreboot.rom add -n grub.cfg -f grub.cfg -t raw</b> + </p> + + <p> + Now display ROM contents again and see that it exists again:<br/> + <b>$ ./cbfstool libreboot.rom print</b> + </p> + + <p> + <b> + Now you have a modified ROM. Refer back to <a href="../install/index.html#flashrom">../install/index.html#flashrom</a> for information + on how to flash it. Once you have done that, shut down and then boot up with your new configuration. + </b> + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <h2 id="troubleshooting">Troubleshooting</h2> + + <p> + A user reported that segmentation faults occur with cbfstool + when using this procedure depending on the size of the grub.cfg being re-insterted. + In his case, a minimum size of 857 bytes was required. This could (at the time of + this release) be a bug in cbfstool that should be investigated with the coreboot + community. If cbfstool segfaults, then keep this in mind. 'strace' (or gdb? clang?) + could be used for debugging. This was in libreboot 5th release (based on coreboot + from late 2013), and I'm not sure if the issue perists in the current releases. + I have not been able to reproduce it. strace (from that user) is here: + <a href="cbfstool_libreboot5_strace">cbfstool_libreboot5_strace</a>. + The issue has been reported by a few users, so it does not happen all the time: + this bug (if it still exists) could (should) be reproduced. + </p> + + <p> + <a href="#pagetop">Back to top of page.</a> + </p> + +<hr/> + + <p> + Copyright © 2014 Francis Rowe <info@gluglug.org.uk><br/> + This document is released under the Creative Commons Attribution-ShareAlike 4.0 International Public License and all future versions. + A copy of the license can be found at <a href="../license.txt">../license.txt</a>. + </p> + + <p> + This document is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See <a href="../license.txt">../license.txt</a> for more information. + </p> + +</body> +</html> |