Android Studio: /dev/kvm device permission denied

Question

When I try to run my Android app on an emulator I get this error:

/dev/kvm permission denied.

I checked the permissions and ad

Answer 1

Under Ubuntu, the permissions of /dev/kvm usually look like this:

$ ls -l /dev/kvm
crw-rw---- 1 root kvm 10, 232 May 24 09:54 /dev/kvm

The user that runs the Android emulator (i.e. your user) needs to get access to this device.

Thus, there are basically 2 ways how to get access:

• Make sure that your user is part of the kvm group (requires a re-login of your user after the change)
• Widen the permissions of that device such that your user has access (requires a change to the udev daemon configuration)

Add User to KVM Group

Check if your user is already part of the kvm group, e.g.:

$ id 
uid=1000(juser) gid=1000(juser) groups=1000(juser),10(wheel)

If it isn't then add it with e.g.:

$ sudo usermod --append --groups kvm juser

After that change you have to logout and login again to make the group change effective (check again with id).

Widen Permissions

Alternatively, you can just can widen the permissions of the /dev/kvm device.

Example:

echo 'KERNEL=="kvm", GROUP="kvm", MODE="0666", OPTIONS+="static_node=kvm"' \
    | sudo tee /etc/udev/rules.d/99-kvm4all.rules
sudo udevadm control --reload-rules
sudo udevadm trigger --name-match=kvm

FWIW, this is the default on other distributions such as Fedora and CentOS.

Check the effectiveness of the above commands with another ls. You should see output similar to:

$ ls -l /dev/kvm
crw-rw-rw-. 1 root kvm 10, 232 2020-05-16 09:19 /dev/kvm

Big advantage: You don't need to logout and login again for this change to be effective.

Non-Solutions

• calling chmod and chown directly on /dev/kvm - 1) these changes aren't persistent over reboots and 2) since /dev/kvm permissions are controlled by the udev daemon, it can 'fix' its permissions at any time, e.g. after each emulator run
• adding executable permissions to /dev/kvm - your emulator just requires read and write permissions
• changing permissions recursively on /dev/kvm - I don't know what's up with that - looks like cargo cult
• installing extra packages like qemu - you already have your emulator installed - you just need to get access to the /dev/kvm device