run skype in a virtual $HOME

$ cd ~/bin
$ cat isolate
#!/bin/bash

export USER=user ## << set username here
sudo unshare -m -- /home/$USER/bin/.run_unshared.sh "$@"

$ cat .run_unshared.sh
#!/bin/bash

USER=user ## << set username here

nsname="${1////_}"
root="$HOME/.unshared/$nsname"
[[ -d "$root" ]] || {
    mkdir -p "$root" || {
        echo Cannot create the isolated directory "$root"
        exit 1
    }
    chown "$USER:" "$root"
}

mount -o bind "$root" $HOME
cd $HOME
sudo -u "$USER" -- "$@"

# usage:
# ~/bin/isolate skype
# the skype will see ~/.unshared/skype as its $HOME