If you've installed successfully in legacy mode but had to change some kernel parameters for it to work, you should try installing in UEFI mode with the same parameters.
**Change xen configuration directly in an iso image**
01. Get EFI partition boundaries `parted Qubes-R4.0-rc4-x86_64.iso unit B print`
02. Using the start address and the size of the EFI partition, setup a loop device for it `sudo losetup -o 524288 --sizelimit 30562304 /dev/loop0 Qubes-R4.0-rc4-x86_64.iso`
03. Mount the loop device `sudo mount /dev/loop0 /mnt`
04. Edit `EFI/BOOT/BOOTX64.cfg` to add your params to the `kernel` configuration key
05. Save your changes, unmount and dd to usb device
Cannot start installation, installation completes successfully but then BIOS loops at boot device selection, hangs at four penguins after choosing "Test media and install Qubes OS" in GRUB menu
There is some [common bug in UEFI implementation](http://xen.markmail.org/message/f6lx2ab4o2fch35r), affecting mostly Lenovo systems, but probably some others too. You can try existing workaround:
06. Execute `mount | grep boot/efi` and note device name (first column). It should be something like `/dev/sda1`.
07. Execute `efibootmgr -v`, search for `Qubes` entry and note its number (it should be something like `Boot0001` - `0001` is an entry number).
08. Replace existing `Qubes` entry with modified one. Replace `XXXX` with entry number from previous step, `/dev/sda` with your disk name and `-p 1` with `/boot/efi` partition number):
09. Compare new entry with the old one (printed in step 6) - it should only differ in additional options at the end, and look probably something like this:
Some Dell systems and probably others have [another bug in UEFI firmware](http://markmail.org/message/amw5336otwhdxi76). And there is another workaround for it:
<bname="f1">1</b> If you use rEFInd, you can see 3 options regarding the USB installer. Choose "Fallback Boot Loader" to enter the GRUB menu. [↩](#a1-1) [↩](#a1-2)
Some systems can freeze with the default UEFI install options.
You can try the following to remove `noexitboot` and `mapbs`.
If you have an Nvidia card, see also [Nvidia Troubleshooting](/doc/nvidia-troubleshooting/#disabling-nouveau).
1. Follow the [steps above](/doc/uefi-troubleshooting/#change-installer-kernel-parameters-in-uefi) to edit the `[qubes-verbose]` section of your installer's `xen.cfg`.
You want to comment out the `mapbs` and `noexitboot` lines.
2. Boot the installer and continue to install as normal, but don't reboot the system at the end when prompted.
3. Go to `tty2` (Ctrl-Alt-F2).
4. Use your preferred text editor (`nano` works) to edit `/mnt/sysimage/boot/efi/EFI/qubes/xen.cfg`, verifying the `noexitboot` and `mapbs` lines are not present.
This is also a good time to make permanent any other changes needed to get the installer to work, such as `nouveau.modeset=0`.
On some early, buggy UEFI implementations, you may need to disable EFI under Qubes completely.
This can sometimes be done by switching to legacy mode in your BIOS/UEFI configuration.
If that's not an option there, or legacy mode does not work either, you can try the following to add `efi=no-rs`.
1. Follow the [steps above](/doc/uefi-troubleshooting/#change-installer-kernel-parameters-in-uefi) to edit the `[qubes-verbose]` section of your installer's `xen.cfg`.
You want to modify the `efi=attr=uc` setting and comment out the `mapbs` and `noexitboot` lines.
2. Boot the installer and continue to install as normal, until towards the end when you will receive a warning about being unable to create the EFI boot entry.
Click continue, but don't reboot the system at the end when prompted.
3. Go to `tty2` (Ctrl-Alt-F2).
4. Use your preferred text editor (`nano` works) to edit `/mnt/sysimage/boot/efi/EFI/qubes/xen.cfg`, adding the `efi=no-rs` option to the end of the `options=` line.
6. Go back to `tty6` (Ctrl-Alt-F6) and click `Reboot`.
7. Continue with setting up default templates and logging in to Qubes.
Whenever there is a kernel or Xen update for Qubes, you will need to follow these [other steps above](/doc/uefi-troubleshooting/#boot-device-not-recognized-after-installing) because your system is using the fallback UEFI bootloader in `[...]/EFI/BOOT` instead of directly booting to the Qubes entry under `[...]/EFI/qubes`.
