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25 April 2020

Could not open /dev/vmmon in VMWare under Ubuntu 20.04

by Jean-Michel Frouin


If you cannot launch a virtual machine under VMWare in Ubuntu, it’s probably because you use Secure Boot (Encrypted partition) and need to sign all kernel modules.

In order to do that (And to did it again when kernel is upgrade), I wrote a script (In fact a copy/paste from



echo "Problems with vmmon and vmnet modules, it's normal"
sudo vmware-modconfig --console --install-all

if [ -f "$PRIV_FILE" ]; then
		echo "$PRIV_FILE present, no need to regenerated"
		echo "$PRIV_FILE missing, generating a new one"
		openssl req -new -x509 -newkey rsa:2048 -keyout $PRIV_FILE -outform DER -out $DER_FILE -nodes -days 36500 -subj "/CN=VMWARE/"

echo "Now sign the two kernel modules (monitor and net)"
echo "This step is need when kernel is updated"
sudo /usr/src/linux-headers-$(uname -r)/scripts/sign-file sha256 $PRIV_FILE $DER_FILE $(modinfo -n vmmon)
sudo /usr/src/linux-headers-$(uname -r)/scripts/sign-file sha256 $PRIV_FILE $DER_FILE $(modinfo -n vmnet)

echo "Check modules signed"
tail $(modinfo -n vmmon) | grep "Module signature appended"

echo "Test if certs is already enrolled if not we need to import it in mok"
sudo mokutil --test-key VMWARE15.der

#echo "Importing the trusted key in our MOK"
#echo "Enter a bit long password like 1515vmware"
#sudo mokutil --import VMWARE15.der