96 lines
3.4 KiB
Markdown
96 lines
3.4 KiB
Markdown
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---
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title: Linux guides
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x-toc-enable: true
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...
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NOTE: This guide pertains to x86 hosts, and does not cover supported CrOS/ARM
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chromebooks. For ARM targets, you should refer to u-boot documentation.
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This page is useful for those who wish to use the GRUB GRUB payload directly.
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If you're using SeaBIOS, the boot process will work similarly to traditional
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BIOS systems; refer to the SeaBIOS documentation
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on <https://seabios.org/SeaBIOS>
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Linux is generally assumed, especially for Libreboot development, but Libreboot
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also works quite nicely with [BSD systems](../bsd/).
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Useful links
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============
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Refer to the following pages:
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* [How to Prepare and Boot a USB Installer in libreboot Systems](grub_boot_installer.md)
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* [Modifying the GRUB Configuration in libreboot Systems](grub_cbfs.md)
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* [How to Harden Your GRUB Configuration, for Security](grub_hardening.md)
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Encrypted (LUKS/dm-crypt) installations
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=======================================
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A better solution for encryption would be a Linux payload in flash, handling the
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encryption, at least if you want to use Linux, because then it'll have
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perfect LUKS support.
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GRUB otherwise has good filesystem support, so if you have a valid `grub.cfg`
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in `/boot/grub` on your installed system, Libreboot's GRUB configuration has
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logic in it that will try to automatically use whatever you have installed,
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by switching to it. In this way, most installations Just Work, so long as
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the `/boot` partition is accessible.
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Full encryption for basic LUKS2 is supported in libreboot.
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See [the guide](encryption.md) for more detail.
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[The ZFSbootmenu guide](zfsbootmenu.md) builds upon the main encryption guide but describes a setup with ZFS native encryption and ZFSbootmenu.
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Rebooting system in case of freeze
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===================================
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Linux kernel has a feature to do actions to the system any time, even
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with it freezes, this is called a
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[Magic SysRq keys](https://en.wikipedia.org/wiki/Reisub). You can do these
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actions with Alt + Sysrq + Command. These are the actions:
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* Alt + SysRq + B: Reboot the system
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* Alt + SysRq + I: Send SIGKILL to every process except PID 1
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* Alt + SysRq + O: Shut off the system
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If some of them don't work, you have to enable it in the kernel
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command line paramter. So append `sysrq_always_enabled=1` to your
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`GRUB_CMDLINE_LINUX_DEFAULT` in `/etc/default/grub`
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You can also run `# sysctl kernel.sysrq=1` to enable them.
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Fedora won't boot?
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==================
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This may also apply to CentOS or Redhat. Chroot guide can be found on
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[fedora website](https://docs.fedoraproject.org/en-US/quick-docs/bootloading-with-grub2/#restoring-bootloader-using-live-disk)
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linux16 issue
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-------------
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Libreboot's default GRUB config sources fedora's grub config
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`grub.cfg` (in `/boot/grub2/grub.cfg`), fedora by default makes use of the
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`linux16` command, where it should be saying `linux`
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Do this in fedora:
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Open `/etc/grub.d/10_linux`
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Set the `sixteenbit` variable to an empty string, then run:
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grub2-mkconfig -o /boot/grub2/grub.cfg
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BLS issue
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---------
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With [newer versions of fedora](https://fedoraproject.org/wiki/Changes/BootLoaderSpecByDefault),
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scripts from grub package default to generating [BLS](https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/)
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instead of `grub.cfg`. To change that behaviour add following line
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to `/etc/default/grub` (or modify existing one if it already exists):
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GRUB_ENABLE_BLSCFG=false
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Then generate `grub.cfg` with:
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grub2-mkconfig -o /boot/grub2/grub.cfg
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