thibaut noah wrote:
Why would i do that? grub needs to have /boot in first position on the
disk?
That is not correct. The grub.cfg file specifies the /boot directory.
For example 'set root (hd1,3)' would set the /boot directory as sdb3
assuming that /boot is a stand-alone partition.
Not at all, i don't have ANY Physical disk, i have two virtual disks (said
it earlier) and what i do is creating another virtual machine with just the
virtual drive of lfs
and i want to boot like this.
How is your second drive, sdb, partitioned? Does it use a GPT or MSDOS
partition table. If GPT, it needs a separate bios_grub partition that is
not formatted at all. Grub uses that as a raw partition when grub_install
runs. /boot is separate. For an MSDOS partition table, the first
partition should start at a 1MB boundary (not sector 63). Grub then
installs its needed data in the unformatted region between the first
sector and the first partition.
* said grub will need to know what are the _real_ partitions on sda that
'/' and '/boot' are on.
Not really. The only thing grub needs to know is where to find the
kernel. Since it does not know where to find fstab, it has to be told
with the set root command or the location of the kerenl has to be
specified explicitly like:
linux (hd1,3)/vmlinuz-version root=/dev/sda4
The root= on the command line is the *kernel's* view of the disk layout.
Grub's view is often different.
Please note that my fstab and my grub file have been made with the
assumption that by having one disk only sdb would become sda on the new
virtual machine.
fstab :
1. /dev/sda1 / ext4 defaults 1 1
2. /dev/sda2 swap swap pri=1 0 0
3. /dev/sda3 /boot ext2 defaults 1 1
4. proc /proc proc nosuid,noexec,nodev 0 0
5. sysfs /sys sysfs nosuid,noexec,nodev 0 0
6. devpts /dev/pts devpts gid=5,mode=620 0 0
7. tmpfs /run tmpfs defaults 0 0
8. devtmpfs /dev devtmpfs mode=0755,nosuid 0 0
Fine for an MSDOS partition table.
grub.cfg :
1. # Begin /boot/grub/grub.cfg
2. set default=0
3. set timeout=5
4.
5. insmod ext2
6. set root=(hd0,3)
7.
8. menuentry "GNU/Linux, Linux 4.4.2-noah" {
9. linux /vmlinuz-4.4.2-tnoah root=/dev/sda1 ro
10. }
- Disk /dev/sdb: 15 GiB, 16106127360 bytes, 31457280 sectors
- Units: sectors of 1 * 512 = 512 bytes
- Sector size (logical/physical): 512 bytes / 512 bytes
- I/O size (minimum/optimal): 512 bytes / 512 bytes
- Disklabel type: gpt
- Disk identifier: F700B567-368F-4096-BB5B-6B2A5C670F10
-
- Device Start End Sectors Size Type
- /dev/sdb1 2048 20973567 20971520 10G Linux filesystem
- /dev/sdb2 20973568 29362175 8388608 4G Linux filesystem
- /dev/sdb3 29362176 31457246 2095071 1023M BIOS boot
This is your problem. It is inconsistent with the above. First, sdb3 is
way bigger than it needs to be. 1M is recommended, not 1023. If you
formatted it as ext2 then that is wrong. What I suggest is deleting
/dev/sdb3 and creating a new 1M /dev/sdb3 and a new 100M /dev/sdb4 to be
mounted as /boot. sdb3 needs to be of type BIOS Boot and sdb4 should be
Linux filesystem. This is what I have:
Device Start End Sectors Size Type
/dev/sda1 2048 4095 2048 1M BIOS boot
/dev/sda2 4096 395263 391168 191M Linux filesystem
/dev/sda3 395264 39456767 39061504 18.6G Linux filesystem
Where sda2 is /boot and sda3 is /
If you make the changes to your system that I suggest, then grub.cfg needs
to be changed to set root=(hd0,4) and change fstab device for /boot to
sda4. Of course you will need to repopulate /boot with the kernel and
rerun grub-install.
-- Bruce
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