One problem that may occur when multiple Linux systems are installed

The article is reproduced from:
Http://www.xnlinux.cn/thread-1753-1-1.html

In a Linux File System, Hard Disk Partitions start from 1, and the first SDA partition is sda1, but grub starts from 0 when identifying hard disk partitions, sda1 is identified as hd0 and 0 by grub. You only need to pay attention to this.

My computer was previously installed with win7 and ubuntu10.04, and rhel6 was recently installed. As a result, the startup items of ubuntu were lost.

Then, enter the Red Hat, sudo VI/boot/GRUB/grub. conf.

Then enter the Ubuntu file system, sudo VI/boot/GRUB/grub. conf

Then sudo fdisk-l

Add the Ubuntu information listed in the grub file in Ubuntu to the grub file in the red hat according to the format of the grub file. Restart the file. Although the startup Item is available, it still cannot be started. The prompt is: cannot mount selected partition

After a long struggle, I almost unmounted ubuntu...

Later, I googled an error message and found out the problem. All the original problems were attributed to a number...
Title Ubuntu
Root (hd0, 7)
Kernel/boot/vmlinuz-2.6.32-21-generic root = UUID = e9f9d111-8ba2-448b-95d9-92c36dc13f52 Ro quiet splash
Initrd/boot/initrd. img-2.6.32-21-generic
This is the Ubuntu information in the red hat grub file, where root (hd0, 7)
Note that
I have sudo fdisk-l again.
Device boot start end blocks ID system
/Dev/sda1 3679 10230 52628940 83 Linux
/Dev/sda2*10231 17242 56323890 7 HPFs/NTFS
/Dev/sda3 17243 38913 174072277 F w95 ext 'd (LBA)
/Dev/sda4 1 3678 29542400 83 Linux
/Dev/sda5 17243 24890 61432528 + 7 HPFs/NTFS
/Dev/sda6 24891 31265 51207156 7 HPFs/NTFS
/Dev/sda7 31266 38404 57343986 83 Linux
/Dev/sda8 38405 38913 4088511 82 Linux swap/Solaris
I suddenly found that Ubuntu corresponds to/dev/sda7. In this case, it should correspond to root (hd0, 6) in the grub file)
Change to 6, restart, OK