http://mowson.org/karl/2016/2016-05-20_alpinelinux_vm_under_virtualbox/
If for example apk add is slow try to disable IPv6 (very slow download starts / installs if the network doesn't support IPv6)
To do this add net.ipv6.conf.all.disable_ipv6 = 1 and run sysctl -p to activate the option.
To temporarily set it run sysctl -w net.ipv6.conf.all.disable_ipv6=1 (no spaces).
To check if IPv6 is disabled: ifconfig shouldn't show an IPv6 anymore (no restart needed).
Unfortunately at restart an error will come up: sysctl: error: 'net.ipv6.conf.all.disable_ipv6' is an unknown key
To solve this the ipv6 modules has to be loaded at the time sysctl is called. Do this by adding ipv6 to /etc/modules
Comment the (last) line in /etc/inittab:
#ttyS0::respawn:/sbin/getty -L 115200 ttyS0 vt100
Otherwise every 10 seconds you'll get the following messages:
Jun 4 09:24:12 alpine daemon.info init: process '/sbin/getty -L 115200 ttyS0 vt100' (pid 1905) exited. Scheduling for restart.
Jun 4 09:24:12 alpine daemon.info init: starting pid 1906, tty '/dev/ttyS0': '/sbin/getty -L 115200 ttyS0 vt100'
Jun 4 09:24:12 alpine auth.err getty[1906]: tcgetattr: I/O error^M
Jun 4 09:24:12 alpine kern.warn kernel: [ 152.014434] ttyS ttyS0: tty_port_close_start: tty->count = 1 port count = 2
Install dedicated program implementations if the speed is of concern. Some reported that for example the busybox grep is a lot slower than the special implementation.