Run Tails on VirtualBox like external usb drive

gistfile1.txt

Step 1: Prepare disk image
Download the USB image of Tails from the project's website

Convert the downloaded image to VDI format:

$ VBoxManage convertfromraw Tails-amd64-5.1.img Tails.vdi --format vdi

(NOTE: the .img file is no longer required after this and may be deleted)

Resize the VDI to make room for the persistent volume:

$ VBoxManage modifyhd Tails.vdi --resize 16384

(NOTE: use 8000 MB + <desired-size-of-persistent-volume-in-MB> as resize value)

Step 2: Set up virtual machine
Follow the instructions provided on the project's website to set up a new VM for Tails

Change the following settings of the newly created VM:

System -> Motherboard -> Extended Features -> ☑ Enable EFI (special OSes only)

(NOTE: required to be able to boot from USB storage)

Storage -> Add new storage controller (leftmost icon at the bottom) -> USB

Storage -> Controller: USB -> Add new storage attachment (third icon from the left at the bottom) -> Hard Disk -> Select VDI image created in Step 1

Set VM resolution (optional):

$ VBoxManage setextradata <vm-name> VBoxInternal2/EfiGraphicsResolution <resolution>

(NOTE: supply <resolution> in format 'WIDTHxHEIGHT', e.g. '1600x900')

Step 3: Boot virtual machine, set up persistent volume
Start the virtual machine

From the boot menu, select Tails (External Hard Disk)

(NOTE: refer to this answer on how to permanently modify the boot menu if desired)

Once Tails has booted up, select Applications -> Tails -> Configure persistent volume to set up the persistent volume