If you are facing issues when booting using UEFI mode, see the [UEFI troubleshooting guide](/doc/uefi-troubleshooting/).
There are a variety of other problems that could arise when using a USB installation medium, and some of the issues can be fixed by doing one or more of the following:
* **Use a different USB drive:**
If possible, try several drives of different sizes and formats.
Some laptops cannot read from an external boot device larger than 8GB.
If you encounter a black screen when performing an installation from a USB stick, ensure you are using a USB drive less than 8GB, or a partition on that USB less than 8GB and of format FAT32.
If installation fails after using one tool, try a different one.
For example, if you are facing trouble installing Qubes after writing the ISO using Rufus, then try using other tools like balenaEtcher or the ``dd`` command.
## "Warning: dracut-initqueue timeout - starting timeout scripts" during installation
This error message is related to the faulty creation of the USB installation medium. If you receive this error message during installation, please make sure you have followed the instructions on [how to write your ISO to a USB key](/doc/installation-guide/#copying-the-iso-onto-the-installation-medium). Specifically, the ``dd`` command listed on that page has been verified to solve this issue on multiple Qubes installation versions.
If the boot screen does not appear, there are several options to troubleshoot.
First, try rebooting your computer.
If it still loads your currently installed operating system or does not detect your installation medium, make sure the boot order is set up appropriately.
The process to change the boot order varies depending on the currently installed system and the motherboard manufacturer.
If **Windows 10** is installed on your machine, you may need to follow specific instructions to change the boot order.
This may require an [advanced reboot](https://support.microsoft.com/en-us/help/4026206/windows-10-find-safe-mode-and-other-startup-settings).
For more information, look at the [Nvidia Troubleshooting guide](https://github.com/Qubes-Community/Contents/blob/master/docs/troubleshooting/nvidia-troubleshooting.md#disabling-nouveau).
If you are facing this problem on an Apple computer, check out the [Macbook Troubleshooting guide](https://github.com/Qubes-Community/Contents/blob/master/docs/troubleshooting/macbook-troubleshooting.md).
If you are installing Qubes 4.0 on an external storage device, you may have forgotten to disable `sys-usb` during the [initial setup](/doc/installation-guide/#initial-setup), which is generally required for that setup to work.
This issue occurs due to the network card, which may be missing some drivers or is incompatible with Qubes.
First, install all available drivers for the card.
You can install the drivers without internet access by first downloading them on another machine, then transferring them over to the current machine (e.g., with a USB drive).
If installing the available drivers does not help, disable the network card in the BIOS and perform the installation before re-enabling the card.
If this solves the issue, it confirms the PCI card is incompatible with Qubes.
In this case, you may want to consider replacing it with a network card of a different brand.
Broadcom cards are notoriously problematic with Qubes.
If the setting is not configured correctly, it means that your hardware won’t be able to leverage some Qubes security features, such as a strict isolation of the networking and USB hardware.
In Qubes 4.0, the default installation won't function properly without IOMMU, as default sys-net and sys-usb qubes require IOMMU. It is possible to configure them to reduce isolation and not use IOMMU by changing virtualization mode of these two VMs to "PV".
In Qubes 4.1, the default sys-net and sys-usb qubes need additional configuration to be usable without an IOMMU. Otherwise they will fail to start with this error message:
```
Start failed: internal error: libxenlight failed to create new domain 'sys-net', see /var/log/libvirt/libxl/libxl-driver.log for details
```
To confirm that a missing IOMMU is causing this problem, check for the following error message in `/var/log/libvirt/libxl/libxl-driver.log`:
```
2022-03-01 13:27:17.117+0000: libxl: libxl_create.c:1146:libxl__domain_config_setdefault: passthrough not supported on this platform
Here are the steps to fix this. Note that this allows sys-net and sys-usb to take complete control of the system, as described in the [FAQ here](/faq/#why-is-vt-damd-viamd-iommu-important):
