安装完ubuntu 9.04启动到grub时出现waiting for loading…后提示找不到root device，然后跳入initramfs，这时如果运行exit可以进入系统说明rootdelay时间太短了，解决办法：
sudo vi /boot/grub/menu.lis
可以看到要启动的grub项目：
## ## End Default Options ##
title Ubuntu 9.04, kernel 2.6.28-11-server
uuid c757c22c-b798-433a-b284-8bca8e084406
kernel /vmlinuz-2.6.28-11-server root=/dev/mapper/shangri--la-root ro quiet splash
initrd /initrd.img-2.6.28-11-server
quiet
title Ubuntu 9.04, kernel 2.6.28-11-server (recovery mode)
uuid c757c22c-b798-433a-b284-8bca8e084406
kernel /vmlinuz-2.6.28-11-server root=/dev/mapper/shangri--la-root ro single
initrd /initrd.img-2.6.28-11-server
title Ubuntu 9.04, memtest86+
uuid c757c22c-b798-433a-b284-8bca8e084406
kernel /memtest86+.bin
quiet
这里在第一项里面的kernel行中加入rootdela=90如下：
## ## End Default Options ##
title Ubuntu 9.04, kernel 2.6.28-11-server
uuid c757c22c-b798-433a-b284-8bca8e084406
kernel /vmlinuz-2.6.28-11-server root=/dev/mapper/shangri--la-root ro quiet splash rootdelay=90
initrd /initrd.img-2.6.28-11-server
quiet
title Ubuntu 9.04, kernel 2.6.28-11-server (recovery mode)
uuid c757c22c-b798-433a-b284-8bca8e084406
kernel /vmlinuz-2.6.28-11-server root=/dev/mapper/shangri--la-root ro single
initrd /initrd.img-2.6.28-11-server
title Ubuntu 9.04, memtest86+
uuid c757c22c-b798-433a-b284-8bca8e084406
kernel /memtest86+.bin
quiet
重启后正常。