Could not find the root block device (in Gentoo)
Solution 1
Finally, I figured it out after several days have gone.It is caused by driver problem. My Gentoo is installed in my external hard-disk connected with my laptop by a USB cable.However, the USB Mass Storage Support option wasn't masked build-in when I built my kernel.Hence, it always blocked in that way.If some are in the same boat with me, and you make sure you have compiled all the referenced file system as built-in, please check if the options as follows are built-in in your kernel.
Device Driver-->USB Support -->USB Mass Storage SupportDevice Driver-->USB Support -->xHCI HCD (USB 3.0) supportDevice Driver-->USB Support --> EHCI HCD (USB 2.0) supportDevice Driver-->USB Support --> UHCI HCD (most Intel and VIA) supportDevice Driver-->USB Support --> Support for Host-side USB
If they don't, check it on.
Solution 2
Maybe it's the wrong hard drive in your grub.cfg
bios=hd1,msdos2 --hint-efi=hd1,msdos2 --hint-baremetal=ahci1,msdos2
hd1,msdos2, ahci1,msdos2 etc. would refer to the second disk. Usually it's the first hd0,msdos1 having the grub installed on /dev/sda
check this with grub-install --recheck /dev/sda
Your partitions would look like this. (boot on primary)
sudo parted -l
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sda: 107GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1049kB 103GB 103GB primary ext4 boot
2 103GB 107GB 4394MB extended
5 103GB 107GB 4394MB logical linux-swap(v1)
Solution 3
To be honest I think the easiest way to do this is to just make a generic kernel.
I simply grab Ubuntu's kernel config, issue a make oldconfig and let genkernel --no-clean --menuconfig all do the rest.
- Emerge the kernel as Quick Install Guide tells you to.
- Grab the generic kernel config:
1) Find the file you want. The most recent kernel version basically: http://kernel.ubuntu.com/~kernel-ppa/configs/
2)wget -O /usr/src/linux/.config kernelconfigurl - Run
make oldconfig. Just hold "Enter" if you don't know how to answer these. No, nothing bad will happen, it will default to the default answer, which is what you should pick in a generic kernel anyway. - Run genkernel with
genkernel --no-clean --menuconfig all. In the menu you can modify things if you wish, or you can just exit. And the install will commence. - Generate your GRUB config with
grub-mkconfig -o /boot/grub/grub.cfg
This kernel will contain almost all modules and whatnot. So everything you plug in will work. Some Unix veterans frown upon generic kernels. If you ran Ubuntu, Fedora, or basically any distribution whatsoever - you used generic kernels.
Do you want to make a minimal kernel without messing up?
No problem. After you boot this kernel, simply plug in all devices you will ever need. Once done, go into /usr/src/linux and issue make localmodconfig. Great, now you have a kernel with only the stuff you will need. Use genkernel to compile the new minimalistic version and install it the same way.
Good luck.
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ResRelentelss
Updated on September 18, 2022Comments
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ResRelentelss over 1 year
There are some trivial troubles that always obsess me.My Gentoo always complains '
Could not find the root block device in UUID=5f7c7e13-2a46-4ae4-a8c0-f77f84e80900' and stuck,once I try to boot. However, if I type the same device name/dev/sda2in, the system goes on.I don´t know why. My Gentoo was installed in one partition/dev/sda2and I mounted/into/dev/sda2.I also have found some posts on the internet. Most posts say it is caused by kernel config,and compiling the corresponding
fsas built-in into the kernel ,not as module can solve it.some saysrootfsshould be specified in grub after thekernelcommand, device name afterrootcommand in grub should be substituted by theUUID. I did it all, but those didn't work.Here is my configuration in grub.
533 menuentry 'Gentoo (on /dev/sda2)' --class gentoo --class linux-gnu --class os $menuentry_id_option 'osprober-chain-225E1F815E1F4D43' { 534 insmod part_msdos 535 insmod ext4 536 set root='hd0,msdos2' 537 if [ x$feature_platform_search_hint = xy ]; then 538 ¦ ¦ search --no-floppy --fs-uuid --set=root --hint- bios=hd1,msdos2 --hint-efi=hd1,msdos2 --hint-baremetal=ahci1,msdos2 5f7c7e13-2a46-4ae4-a8c0-f77f84e80900 539 ¦ else 540 ¦ ¦ search --no-floppy --fs-uuid --set=root 5f7c7e13-2a46-4ae4-a8c0-f77f84e80900 541 ¦ fi 542 ¦ ¦ echo 'Loading Linux x86_64-4.4.39-gentoo ...' 543 ¦ ¦ linux /boot/kernel-genkernel-x86_64-4.4.39-gentoo root=UUID=5f7c7e13-2a46-4ae4-a8c0-f77f84e80900 ro 544 ¦ echo 'Loading initial ramdisk ...' 545 ¦ ¦ initrd /boot/initramfs-genkernel-x86_64-4.4.39-gentoo 546 ¦ boot 547 548 }The Gentoo coexists with Ubuntu.
My
/etc/fstab.1 # /etc/fstab: static file system information. 2 # 3 # noatime turns off atimes for increased performance (atimes normally aren't 4 # needed); notail increases performance of ReiserFS (at the expense of storage 5 # efficiency). It's safe to drop the noatime options if you want and to 6 # switch between notail / tail freely. 7 # 8 # The root filesystem should have a pass number of either 0 or 1. 9 # All other filesystems should have a pass number of 0 or greater than 1. 10 # 11 # See the manpage fstab(5) for more information. 12 # 13 14 # <fs> <mountpoint> <type> <opts> <dump/pass> 15 16 # NOTE: If your BOOT partition is ReiserFS, add the notail option to opts. 17 UUID=5f7c7e13-2a46-4ae4-a8c0-f77f84e80900 / ext4 noatime 0 1 18 UUID=B66EAE686EAE215B /mnt/D/ ntfs errors=remount-ro 19UUID of the corresponding name
/dev/sda2: UUID="5f7c7e13-2a46-4ae4-a8c0-f77f84e80900" TYPE="ext4" PARTUUID="000e21f3-02" /dev/sda4: UUID="B66EAE686EAE215B" TYPE="ntfs" PARTUUID="000e21f3-04"Is there anyone has some ideas? thanks.
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ResRelentelss over 7 years   First of all, thanks @Michael D . I don't know what exactly the difference between
ahciandhd, can you explain it more? And I have triedgrub-install --recheck /dev/sda, not any charm present. Do you mean I should replace/dev/sda2orspecified UUIDtohd1,msdos2? -
Michael D. over 7 yearsI think the first line (from my answer) covers all cases - whether you boot via ´bios´, ´efi´,
ideorahci. AHCI stands for advanced host controller interface and is for sata hard drives which you need to set in the bios. -
Michael D. over 7 yearsAs far as I know, you don't edit the
grub.cfgmanually. You install grub straight to/dev/sda(or/dev/sdb?) - no numbers.update-gruborgrub-mkconfig -o /boot/grub/grub.cfg "$@"generates the file for you -
Michael D. over 7 yearsfinally - here is a tutorial how to re/install/update grub. It's for ubuntu but that might work for gentoo, too. Actually you just need to boot (if you can fix it to boot), login as root and start with the
grub-installline. howtoubuntu.org/… -
ResRelentelss about 7 yearsFirst of all, thank you for your long answer. However, I used the generic kernel option to compile my kernel, but it seems that gen kernel doesn't switch on the
USB Mass Storage Supportkernel option by default, even though I plugged my external USB hard disk in my computer. I think this is the crux which causes this problem. -
Apache about 7 yearsThere is no generic kernel config on Gentoo, that's why I used Ubuntu's configuration. Usingmake localmodconfigonly works once you are on the booted machine (not chroot/livecd). ** Even though the Gentoo wiki says it should work through the LiveCD it failed for me to do so.
