GRUB: Device node not found

mattia29 · n00b Joined: 28 Nov 2015 Posts: 6

Hi everyone,
I'm trying installing Gentoo on virtualbox at the moment, and it was going all well till I tried to install grub. At the command

krinn · Watchman Joined: 02 May 2003 Posts: 7470

You must have forgotten the mount --rbind /dev /mnt/gentoo/dev part of the chroot.
If your /dev is not populated in your chroot, grub cannot see any /dev/sda because you have no /dev/sda in your chroot.

Try redo the chroot part from start and make sure you don't forget to bind /dev before chrooting.

mattia29 · n00b Joined: 28 Nov 2015 Posts: 6

I'm sure I've done it. However I reinstalled from zero with the difference that before I made a GPT partitioning of the virtual hd and now simply MBR. It's going fine now. How did you understand that one was the missing command?
Thank you for your help.

NeddySeagoon · Posted: Tue Dec 01, 2015 8:14 pm Post subject:

mattia29,

It makes little difference if you use a MSDOS or GPT partition table.
Virtualbox emulates a BIOS system so you may have an extra wrinkle or two to iron out to get it to work with GPT.

/dev (along with /proc and /sys) are not real file systems. They are kernel data structures exposed to users as file systems.
/dev is created and maintained by the kernel option DEVTMPFS. udev keeps an eye on new nodes as they are created and fixes groups, permissions and so on.

When you boot the installation media, its /dev gets created at /dev. Lots of things break if this fails.
When you mount your growing install at /mnt/gentoo, the kernel does not create /mnt/gentoo/dev and populate it for you,
That's what the bind mount does. Makes a filesystem appear in several places

When you do the chroot, from inside the chroot, everything outside becomes inacessable. Thus the install medias /dev has vanished and absolute paths like /dev are with respect to what was /mnt/gentoo.
We know that /dev/sda existed outside of the chroot because you partitioned it, made filesystems and so on.
Nothing else tries to operate on devices until you install grub. If that gives a

mattia29 · n00b Joined: 28 Nov 2015 Posts: 6

Thank you for the exhaustive explanation.
I've just begun to use gentoo, it's my first source-based distro. So yes, I have to learn a different approach. As you said, I used to reinstall other distros to fix serious problems, now I'm curious to try the "gentoo-way".
I'm reading the handbook step by step, I hope this should be sufficient to start (probably I would open other threads for help/curiosities if needed).

So, between GPT and MSDOS, which you advice?

NeddySeagoon · Posted: Fri Dec 04, 2015 5:10 pm Post subject:

mattia29,

Both work. As you are doing a Virtualbox guest install an MSDOS partition table will be simpler.
Indeed, the only reasons to use GPT in Virtualbox are
a) that the guest only supports UEFI.
b) the guest HDD will be bigger than 2TiB.

There are other ways to get round b) in Virtualbox.

It is left as a exercise for the (advanced) reader to install Gentoo as a guest on a Windows host, where windows is installed on a FAT filesystem.
The problem is that FAT only supports files up to 2G and you can't install Gentoo in 2G.
You may not tamper with the Windows install in any way, so donating a raw partition to VBox is not permitted.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Section_8 · l33t Joined: 22 May 2004 Posts: 627

NeddySeagoon · Posted: Fri Dec 04, 2015 8:50 pm Post subject:

Section_8,

Thats the second answer. I used mdadm linear raid0 to achieve the same thing.
Lots of 2G volumes stuck end to end.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.