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appnote:efidriverdisconnect [2017/07/27 11:52] (current)
nikize created
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 +====== Disconnecting EFI drivers ======
 +This is notes that might help with debugging issues possibly caused by EFI drivers
 +  * Create a disk image with a FAT32 filesystem with [[https://github.com/tianocore/edk2/raw/master/EdkShellBinPkg/FullShell/X64/Shell_Full.efi|UEFI full shell]], saved as ''\EFI\Boot\BootX64.efi''
 +  * And something to test the scenario with, //(we will assume ''ipxe.efi'', but change for your scenario)// and save it as ''/ipxe.efi'' on the disk
 +  * Boot the troublesome hardware with the just created disk image
 +  * You should get to a UEFI shell prompt.  If you then type ''fs0:'' and ''ls'' you should see your FAT filesystem with ''ipxe.efi''
 +  * If not use ''map'' to find different ''fsX:'' and try them until you find your filesystem.
 +  * Reproduce the issue by running ''ipxe.efi''
 +Get in to the shell again
 +  * use ''drivers -b'' and ''devices -b'' to see a list of handles complete with some kind of textual description
 +//''-b'' is used to get one screen of text at a time//
 +  * Find something plausible, try running ''disconnect <handle>''
 +  * where ''<handle>'' is the 2- or 3-digit hex value of the handle
 +  * and then retry running ''ipxe.efi'' (from the shell, without rebooting first)
 +With Hyper-V as an example we might look for something like: "Hyper-V", "VMBus", "VmbusDxe", "NetVSC", "RNDIS", etc
 +And then looking at ''devices'' for where this is connected to, and try to disconnect it from there
 +=== Alternatives to ''-b'' on long output ===
 +  * Most efi shell commands supports ''-b'' to get paged output
 +  * Most of the time the output is also available on any connected serial port.
 +  * Or pipe output to a file such as ''drivers > drivers.txt'' and then use the editor with ''edit drivers.txt'' to show it (this requires a writable filesystem)
appnote/efidriverdisconnect.txt · Last modified: 2017/07/27 11:52 by nikize
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