Fedora 16 : kernel panic not syncing vfs unable to mount root fs on unknown-block

After upgrading to a new kernel which version is 3.1.9-1 with “yum update” , I’ve faced a kernel panic error when booting 3.1.9-1.

Error message

kernel panic not syncing vfs unable to mount root fs on unknown-block

Seen from /boot directory , there is no initramfs file for 3.1.9-1.

# ls /boot/initramfs-3.1.* /boot/initramfs-3.1.0-7.fc16.i686.PAE.img  /boot/initramfs-3.1.6-1.fc16.i686.PAE.img

initramfs is needed for booting Linux.

I don’t know why there is no initramfs for 3.1.9-1.
There are enough disk space for /boot partition.

Anyway , to resolve this , I need to make an initramfs for kernel 3.1.9-1.

Let’s make the initramfs with dracut.

At first , boot Fedora with a previous kernel  3.1.6-1 which works well.

[root@fc16 ~]# uname -ri 3.1.6-1.fc16.i686.PAE i386

install dracut via yum if you haven’t installed it.

[root@fc16 ~]# yum install dracut

make an initramfs for 3.1.9-1.

[root@fc16 ~]# dracut /boot/initramfs-3.1.9-1.fc16.i686.PAE.img 3.1.9-1.fc16.i686.PAE

nn , there is no modules.dep file for 3.1.9-1..

[root@fc16 ~]# dracut /boot/initramfs-3.1.9-1.fc16.i686.PAE.img 3.1.9-1.fc16.i686.PAE E: FATAL: Could not load /lib/modules/3.1.9-1.fc16.i686.PAE/modules.dep: No such file or directory

actually there is no modules.dep file.. nn why ??

[root@fc16 ~]# ls /lib/modules/3.1.9-1.fc16.i686.PAE/modules.d* /lib/modules/3.1.9-1.fc16.i686.PAE/modules.devname /lib/modules/3.1.9-1.fc16.i686.PAE/modules.drm

Okay , how about  issuing yum-complete-transaction and yum reinstall kernel ?

[root@fc16 ~]#  yum-complete-transaction [root@fc16 ~]# yum reinstall kernel 読み込んだプラグイン:langpacks, presto, refresh-packagekit 再インストール処理の設定をしています 実行中のカーネルを飛ばします: kernel-PAE-3.1.6-1.fc16.i686 依存性の解決をしています --> トランザクションの確認を実行しています。 ---> Package kernel-PAE.i686 0:3.1.0-7.fc16 will be インストール ---> Package kernel-PAE.i686 0:3.1.9-1.fc16 will be インストール

after issuing above commands , initramfs and modules.dep for kernel 3.1.9-1 has been installed.

[root@fc16 ~]# ls /boot/initramfs-3.1.* /boot/initramfs-3.1.0-7.fc16.i686.PAE.img  /boot/initramfs-3.1.9-1.fc16.i686.PAE.img /boot/initramfs-3.1.6-1.fc16.i686.PAE.img [root@fc16 ~]# ls /lib/modules/3.1.9-1.fc16.i686.PAE/modules.d* /lib/modules/3.1.9-1.fc16.i686.PAE/modules.dep /lib/modules/3.1.9-1.fc16.i686.PAE/modules.dep.bin /lib/modules/3.1.9-1.fc16.i686.PAE/modules.devname /lib/modules/3.1.9-1.fc16.i686.PAE/modules.drm

You can check contents of initramfs with lsinitrd

[root@fc16 ~]# lsinitrd /boot/initramfs-3.1.9-1.fc16.i686.PAE.img | head -10 /boot/initramfs-3.1.9-1.fc16.i686.PAE.img: 17M ======================================================================== ======================================================================== drwxr-xr-x   1 root     root            0 Jan 22 23:15 . drwxr-xr-x   1 root     root            0 Jan 22 23:15 run drwxr-xr-x   1 root     root            0 Jan 22 23:15 run/initramfs drwxr-xr-x   1 root     root            0 Jan 22 23:15 run/initramfs/lib -rwxr-xr-x   1 root     root       115376 Oct 27 20:34 run/initramfs/lib/libgcc_s-4.6.2-20111027.so.1 lrwxrwxrwx   1 root     root           28 Jan 22 23:15 run/initramfs/lib/libgcc_s.so.1 -> libgcc_s-4.6.2-20111027.so.1 drwxr-xr-x   1 root     root            0 Jan 22 23:15 run/initramfs/lib/i686

I can boot Fedora with kernel 3.1.9-1 :)

[root@fc16 ~]# uname -ri 3.1.9-1.fc16.i686.PAE i386

If you face “kernel panic not syncing vfs unable to mount root fs on unknown-block” when booting a new kernel , please check whether there exist modules.dep and initramfs for that kernel.
You might solve this by issuing “yum-complete-transaction” and “yum reinstall kernel”.