Windows 10 on Chromebook (Linux 'Crostini' container)

Sharing files between Windows (in Crostini) and Linux (in Crostini)

This was a bit tricky, and nowhere near as easy as using Virtualbox.

In theory, qemu/libvirt (which is started by the Virtual Machine Manager) can start its own samba server instance.

Unfortunately, libvirt does not directly allow access to -net parameters, but it is possible to add those -net parameters using virsh edit.

The resulting XML file should look something like:

<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
    ...
    <qemu:commandline>
        <qemu:arg value='-net'/>
        <qemu:arg value='nic'/>
        <qemu:arg value='-net'/>
        <qemu:arg value='user,smb=/path/to/shared/directory'/>
    </qemu:commandline>
</domain>

…where the reference to xmlns:qemu is added to the domain specification near the top of the file, and the qemu:commandline is a section added to the bottom. The ‘answer’ on stackexchange didn’t have the value='nic' definition, but I found without that section nothing happened. Unfortunately with the value='nic' definition there is a complaint about PCI/argument conflict between the ethernet device and the graphics driver. Changing some PCI values removed the complaint, but it still didn’t work!

Using a command something like:

qemu-system-x86_64 /path/to/windows10.img -enable-kvm -net nic -net user,smb=/path/to/shared/directory -m 1024

did work, but meant I wasn’t using all those wonderful options that libvirt made available. It is possible to see those options in the libvirt log, but I decided to set up a SAMBA share from Crostini/Linux instead.

The guides I used to set up Samba shares on Linux are found on ‘yodiw: install samba Ubuntu 20.04 and Windows 10 sharing’ and reddit ‘Use your chromebook as a samba server!’.

sudo apt-get install samba -y
sudo smbpasswd -a 'username' # the user name. a password will be asked for

Then I edited the smb.conf file in /etc/samba. To use a graphical editor using sudo I used the command xhost +si:localuser:root.

To the [global] part of smb.conf I added

  passdb backend = tdbsam
  security = user

I also added a section to [global] to allow use of symbolic links

  allow insecure wide links = yes

Check interfaces using sudo ifconfig. I used eth0 Edit the interfaces section in smb.conf.

  interfaces = x.x.x.x eth0 # replace x.x.x.x with the IP of the Crostinin container
  bind interfaces only = yes

In the user part, disable bad_user map and force user.

  #map to guest = bad user
  force user = 'username' # replace 'username' with the user

I edited the [homes] section in smb.conf, rather than set up a separate [users] section

[homes]
  comment = Home directories
  browseable = yes
  read only = no
  follow symblinks = yes # only if required to follow symlinks
  wide links = yes # only if required to follow symlinks
  create mask = 0660
  directory mask = 2770
  valid users = %S

Then testparm to test the SAMBA configuration, and restart the samba server.

sudo service smbd restart
sudo service nmbd restart
sudo service smbd status

The share will be at the eth0 IP address found earlier with sudo ifconfig, e.g. 100.115.7.8\username.

The credentials to connect a network drive from Windows will be WORKGROUP\username.