UEFI
UEFI seems like a conceptually good thing since BIOS behavior is based on conventions from the early 80s. But it is a bit of a radical change for some of us. This is an excellent introduction to the topic of UEFI.
Here is an article that talks about removable media installations and how to trick normal OS install processes into doing what you want, including getting Windows back to "the way it was" once you’re USB drive is gone. This article is similarly helpful.
GRUB2
The program grub-mkconfig generates grub.cfg files suitable for
most cases. It is suitable for use when upgrading a distribution, and
will discover available kernels and attempt to generate menu entries
for them.
grub-mkconfig does have some limitations. While adding extra custom
menu entries to the end of the list can be done by editing
/etc/grub.d/40_custom or creating /boot/grub/custom.cfg, changing
the order of menu entries or changing their titles may require making
complex changes to shell scripts stored in /etc/grub.d/. This may be
improved in the future. In the meantime, those who feel that it would
be easier to write grub.cfg directly are encouraged to do so, and to
disable any system provided by their distribution to automatically run
grub-mkconfig.
-
/etc/default/grub- Controlsgrub2-mkconfig. -
grub2-mkconfig -o /boot/grub/grub.cfg- Makes/boot/grub/grub.cfg -
grub2-install- Uses/boot/grub/grub.cfg
|
Note
|
Grub2 uses /boot/grub/grub.*cfg* and not grub.conf like
legacy Grub did. If this is not done correctly, you’ll get a Grub
prompt on boot but no menu. |
timeout=5
default=0
fallback=1
menuentry 'Xed Gentoo' {
linux (hd0,msdos1)/boot/vmlinuz root=/dev/sda1
}
menuentry 'Xed Gentoo (revert to previous kernel)' {
linux (hd0,msdos1)/boot/vmlinuz.old root=/dev/sda1
}# Foreground/background
color_normal=green/black
color_highlight=red/black
menu_color_normal=black/green
menu_color_highlight=black/red
# Forever=-1, Now=0
timeout=10
# Numbering starts at 1 (IS THIS TRUE?)
default=1
# If Grub can not boot the default, this boots.
fallback=2
menuentry "Normal Linux" {
search --set=root --label OS1 --hint hd0,msdos8
linux /boot/vmlinuz root=/dev/sda2
}
# THIS NEEDS TO BE FIXED UNTIL IT IS KNOWN TO WORK.
menuentry "Linux with RAID1" {
search --set=root --label OS1 --hint hd0,msdos8
linux /boot/vmlinuz root=/dev/sda2
initrd /boot/initramfs
}
menuentry "Xen" {
root=hd0,2
multiboot /boot/xen.gz dom0_mem=2048M
module /boot/vmlinuz root=/dev/sda2
}Not in chroot (This didn’t work and needs to be refined.):
grub2-install --boot-directory=/mnt/gentoo/boot --grub-setup=/mnt/gentoo/boot/grub/grub.cfg /dev/sdaHmm… Then I tried just this and it did install ok..
grub2-install /dev/sda
grub2-install /dev/sdbHere’s my Grub2 entry. Note that for Xen, the initramfs is also
module and not initrd as you might expect.
timeout=5
default=0
menuentry 'Xen Hypervisor' {
set root=(md/ssdset)
multiboot /boot/xen.gz dom0_mem=2048M
module /boot/vmlinuz udbg-immortal root=/dev/md0
# NOT initrd !
module /boot/initramfs
}
menuentry 'Xen Hypervisor - netconsole' {
set root=(md/ssdset)
multiboot /boot/xen.gz dom0_mem=2048M
module /boot/vmlinuz udbg-immortal root=/dev/md0 netconsole=4444@192.168.30.208/eth0,6666@192.168.30.8/50:46:5d:a5:18:87
module /boot/initramfs
}
menuentry 'Normal Kernel: vmlinux' {
set root=(md/ssdset)
linux /boot/vmlinuz-3.14.5 root=/dev/md0
initrd /boot/initramfs
}
menuentry 'Normal Kernel: vmlinux netconsole' {
set root=(md/ssdset)
linux /boot/vmlinuz-3.14.5 root=/dev/md0 netconsole=4444@192.168.30.208/eth0,6666@192.168.30.8/50:46:5d:a5:18:87
initrd /boot/initramfs
}
menuentry 'Normal Kernel: vmlinux.old' {
set root=(md/ssdset)
linux /boot/vmlinuz-3.11.6.old root=/dev/md0 netconsole=4444@192.168.30.208/eth0,6666@192.168.30.8/50:46:5d:a5:18:87
initrd /boot/initramfs
}Modules are searched for in /boot/grub/i386-pc/*.mod but it seems
that RAID1 is already included in core GRUB2 (unlike RAID[56]).
Windows
Can GRUB boot Windows? In theory. Here are some things to try.
set root=(hd0,msdos1)
insmod part_msdos
insmod ntfs
ntldr (hd0,msdos1)/bootmgrNote that all or none of this may be important. Also this might be relevant syntax.
chainloader +1Legacy GRUB
Probably best to move on to GRUB2. Here’s a small simple example of an
ordinary old-fashioned configuration file. Note that it is .conf and
not .cfg.
default 0
timeout 8
title=Gentoo Linux
root (hd0,0)
kernel (hd0,0)/vmlinuz
title=Gentoo Linux (previous)
root (hd0,0)
kernel (hd0,0)/vmlinuz.old
title=EXPERIMENTAL Gentoo Linux
root (hd0,1)
# genkernel users:
kernel (hd0,1)/kernel-experimental boot_delay=200 udbg-immortalInstalling can be a real PITA. Sysresc can use grub-install.
Figuring out how to deploy it is not obvious. But this has worked.
grub-install --root-directory=/mnt/ /dev/sdaAt the least it installed some stage1 stuff in the MBR. This can be explicitly checked with something like this.
% dd if=/dev/sda count=1 bs=512 | xxd | grep -B1 RUB
1+0 records in
1+0 records out
512 bytes (512 B) copied, 5.0763e-05 s, 10.1 MB/s
0000170: 06be 947d e830 00be 997d e82a 00eb fe47 ...}.0...}.*...G
0000180: 5255 4220 0047 656f 6d00 4861 7264 2044 RUB .Geom.Hard DYou can blank that out and if grub installation puts it back, you can be pretty sure it’s ok. (Obviously save a copy of the MBR in case you overwrite something important.)
It may be necessary to run just grub or grub --no-floppy for
old-school cases. Then you need this kind of thing.
grub> root (hd0,0)
Filesystem type is ext2fs, partition type 0x83
grub> find /boot/grub/stage1
(hd0,0)
grub> setup (hd0)
Checking if "/boot/grub/stage1" exists... yes
Checking if "/boot/grub/stage2" exists... yes
Checking if "/boot/grub/e2fs_stage1_5" exists... yes
Running "embed /boot/grub/e2fs_stage1_5 (hd0)"... 18 sectors are embedded.
succeeded
Running "install /boot/grub/stage1 (hd0) (hd0)1+18 p (hd0,0)/boot/grub/stage2 /boot/grub/menu.lst"
... succeeded
Done.
grub> quit