"The USB flash drive installs redhat5.5 in the free partition of the hard disk, and grub is installed in the Linux partition (I don't want to install it in mbr), but when it is restarted after installation, it will directly enter Win7 without a startup menu." This means that your grub is not installed in mbr, so you can use easybcd. Enter win7, create a new entry under easybcd, and ask him to transfer the boot right to the boot partition of linux, that is, the path of your/partition (if you don't boot separately) or /boot partition, so grub can boot linux. After booting, there should be two menus created by easybcd, and then choose the one of linux to start grub booting, but at this time, you should enter grub & gt mode. There you set the root, kernel and initialization. . The path of these kernel startup files can enter linux, and then install grb-install into the linux boot partition.