Install VirtualBox guest additions onto Ubuntu server guests

Have tested these instructions successfully under an Ubuntu 16.04LTS guest with a VirtualBox 5.1 and 5.2 host.

Install steps
Mount with guest/host permissions matched
Reference

Install steps

Create Ubuntu server instance under VirtualBox (obviously).
Start VM, goto Devices - Insert Guest Additions CD image to mount the ISO image.

From the terminal, run the following commands:

 $ sudo su
 $ apt install gcc make
 $ mkdir --parents /media/cdrom
 $ mount /dev/cdrom /media/cdrom
 $ /media/cdrom/VBoxLinuxAdditions.run
 $ reboot

After reboot:

 $ sudo usermod --append --groups vboxsf USERNAME

Host shares should now be mounted in Ubuntu guest under /media via the installed VBoxService service, set to start on system boot-up.
All done.

Mount with guest/host permissions matched

By default with auto mounted shares, VirtualBox will set an interesting set of ownership and file/directory permissions for the guest which (for me) is sub-optimal. To correct this behavior and mirror permissions between host and guest we can do the following:

Shut down the guest (if not already) and ensure "Auto-mount" is disabled.
Restart the guest.

From the shell, determine the umask and uid/gid of your host user.

 $ umask
 0022
 $ id
 uid=1000(USERNAME) gid=1000(USERNAME) groups=1000(USERNAME),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),110(lxd),115(lpadmin),116(sambashare)

Now mount the share as follows:

 $ mkdir --parents /path/to/share
 $ sudo mount.vboxsf -o umask=UMASK,uid=UID,gid=GID SHARE_NAME /path/to/share

If all is good, we can now add an entry to our /etc/fstab:

 SHARE_NAME /path/to/share vboxsf umask=UMASK,uid=UID,gid=GID 0 0

And remount all file systems
```
 $ sudo mount -a
```
All done.

jucke/README.md

Install VirtualBox guest additions onto Ubuntu server guests

Install steps

Mount with guest/host permissions matched

Reference