Re: debian installation issue
On Fri, Jun 11, 2021 at 09:38:37PM +0300, Semih Ozlem wrote:
> I reinstalled the system, including an efi partition (500MiB) and the
> problem was fixed.
This suggests that you booted the installer in UEFI mode, rather than in
Legacy mode. If you boot the installer in UEFI mode, you are expected
to install a system that will boot in UEFI mode, which means it needs an
EFI partition (and GPT disk label).
If you wanted to create an install that would boot in Legacy mode, you
need to boot the installer in Legacy mode first.
(Or maybe there's something you can do in Expert mode to work around it;
I don't know. At a bare minimum, you'd need to switch which of the
GRUB packages gets installed -- grub-pc vs. grub-efi.)
> How to check where grub is installed? And what is a friendly guide to
> learning about grub?
GRUB should be installed on the *disk* (not on a partition) that you
intend to boot.
There are two different GRUB packages: grub-efi for UEFI booting, and
grub-pc for Legacy (BIOS) booting. The mode in which you booted the
installer determines which of these gets installed at the end of the
installation.
Legacy (BIOS) booting is the old quasi-standard. It's been around since
the 1980s. In this paradigm, the boot loader code is installed to
something called the "master boot record" (MBR) which is really just the
first few hundred bytes of the disk. Some space is left unpartitioned at
the start of the disk to make room for this. Much hand-waving is involved.
UEFI booting is the new standard. It's been around for several years
now, so it's fairly widespread, but not quite ubiquitous. UEFI booting
requires a GPT disk label (partition table type), and one of the partitions
on the disk must be an EFI partition. This is a FAT-type file system which
contains programs used by the boot loader.
A lot of machine (probably most machines made today) can boot in either of
these two modes, because not everyone has moved over to the new standard
yet. Older machines will only support Legacy booting. A few newer machines
may only support UEFI booting.
Secure Boot (Microsoft's attempt to stop you from using Linux) relies on
UEFI booting, and therefore this was one of the driving forces behind it,
but not the *only* driving force. If your machine doesn't use Secure Boot,
don't worry about it. It won't affect you.
Of course, this is not everything there is to know about UEFI and Legacy
booting, but it might be enough for most purposes, especially if you just
want to install and run Debian, and don't particularly care about the
inner workings.
Next, the care and feeding of GRUB on an installed Debian system:
In the /boot/grub directory there's a file named grub.cfg. This is the
menu that GRUB reads from disk when you boot. It's generated
automatically every time you do certain things (like installing a new
kernel package). If at any time you'd like to regenerate this menu
(because you changed something yourself), you run this command:
update-grub
You should not edit grub.cfg directly, because your changes will be
overwritten eventually.
If you'd like to change how the menu operates, there are a few pieces
you need to know about.
The first is /etc/default/grub which is a file containing lines of shell
code. It's only supposed to contain variable definitions, and these
variables affect the overall menu, or they affect every menu entry.
You can change these variables (e.g. if you'd like the menu timeout to
be a bit longer because your monitor takes several seconds to switch
modes, or if you'd like to remove the "quiet" flag so that you can see
more details of what's happening).
Individual menu entries are generated by shell code fragments in the
/etc/grub.d/ directory. If you'd like to add a menu entry of your own,
you can create a new file in this directory. You'll need some expertise
for this. If you'd like to customize the generated segments of the GRUB
menu, you might consider editing one of the existing files in this
directory, but make sure you have a backup, and a means of booting in
rescue mode, first. This is not something you want to break, especially
if it's a remote system.
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