Red Hat Bugzilla – Bug 1275101
grub.cfg: bug and poor choices by 30_os-prober for menuentry, command, root, parameters
Last modified: 2016-12-20 10:09:21 EST
Description of problem: Installing a new Fedora 23 alongside previous Fedora systems (in other harddrive partitions) results in a /boot/efi/EFI/fedora/grub.cfg that fails to boot the previous systems. Also, the structure and organization of the boot menus is not friendly to common use.
Version-Release number of selected component (if applicable):
How reproducible: always
Steps to Reproduce:
1. UEFI boot Fedora-Live-Workstation-x86_64-23_Beta-3.iso from USB in "Try Fedora" mode on a system that already has previous Fedora systems (such as Fedora 22) installed on other partitions.
2. Install Fedora 23 to harddrive on a new partition, and install new bootloader.
3. Try to boot the old Fedora 22.
Actual results: Fails to boot, with complaints: 'linux': command not found; 'initrd': command not found
Expected results: successful boot of old Fedora 22
The Live USB was booted in UEFI mode on a bare hardware box [no virtualization] with UEFI firmware, and the menuentries for Fedora 23, which were composed by /etc/grub.d/10_linux, have 'linuxefi' and 'initrdefi' for commands, and they work. However, the menuentries for the previous Fedora sytems, composed by /etc/grub.d/30_os-prober, use 'linux' and 'initrd' instead; and those commands are not in the newly-installed grub2. That's a bug, perhaps two bugs. Any command name that is chosen must have an actual implementation installed, and if Fedora 23 boots with linuxefi then 'linuxefi' is the best choice for any other Linux, too.
The Fedora 23 grub command looks like
linuxefi /boot/vmlinuz-4.2.3-300.fc23.x86_64 root=UUID=<the-correct-UUID> ro rhgb quiet LANG=en_US.UTF-8
while the Fedora 22 command looks like
linux /boot/vmlinuz-4.1.10-200.fc22.x86_64 root=/dev/sdb6
Here 30_os-prober has made poor choices:
1) Using /dev/sdb6 instead of UUID=<the-correct-UUID>. There is no guarantee that a device name such as "/dev/sdb6" is stable from boot to boot, even with no hardware changes. Using UUID= protects against this, and also still works if a new drive is installed or if drives are re-arranged.
2) Not supplying the same parameters "ro rhgb quiet LANG=en_US.UTF-8" for other systems. "ro" has been valid and useful for around 20 years. LANG= is newer and perhaps not always recognized [but is for Fedora 22], but causes no harm. Similarly, other unknown parameters are most likely ignored.
The layout of menuentries is poor. They should be sorted in reverse chronological order: newest first. Instead, the 'rescue' entry appears at the top level despite almost never being used. The current sort is by strcmp, so that "4.1.10" comes before "4.1.8", which is a bug in sorting version numbers. Also, the chosen names for sibling submenu entries are all the same, despite being different kernel versions. Thus the user must type 'e' at boot to edit the entry in order to find out which kernel is which. Put the kernel version into the title.
I think this is a duplicate of bug #1274288 (regarding the broken use of "linux"/"initrd" commands instead of "linuxefi"/"initrdefi" in config generated by 30_os-prober).
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