Spawn Linux VMs as Erlang processes in the Erlang VM.

evum makes a Linux virtual machine into an Erlang actor. While the Linux VM has its own state like any other process (memory, system processes, disk), all I/O with the outside world is sent as messages through the Erlang VM (currently working: network, system console).

REQUIREMENTS

sudo apt-get install user-mode-linux

TODO

• persistent state mounted as filesystem

EXAMPLE

Quick Start

• Download and create a buildroot instance

    1> {ok, Ref} = evm:create([
            {label, test1},     % Label identifying this vm
            {dist, buildroot}   % Linux distribution image, defined in priv/evm.cfg
            ]).
    {ok,<0.60.0>}
  
    2> flush(). % See the boot messages
  
    3> evum:send(test1, "hostname").
    4> flush().
    Shell got <<"evm">>
    ok
  

• Download and create an OpenWRT instance with network access

Set the network configuration for your VM in priv/evm.cfg:

{network, [
    {home, [
        {base_ip, "192.168.213."},
            {first_ip, 92},
            {netmask, "255.255.255.0"},
            {gw, "192.168.213.1"}
    ]}
    ]}.

Create the OpenWRT VM:

1> {ok, Ref} = evm:create([
        {label, test2},     % Label for this vm
        {dist, openwrt},    % Defined in priv/evm.cfg
        {net, coffeeshop}   % Set up networking: see priv/evm.cfg
        ]).
{ok,<0.60.0>}

From another host (NOTE: will not work from the system running evum), telnet to the IP address of the OpenWRT VM:

telnet 192.168.213.92 # or: nc -t 192.168.213.92 22

Run some commands in the VM. All the network data is proxied through Erlang:

opkg update # may need to adjust /etc/resolv.conf first
opkg install erlang
erl

Using the Host OS

% Start the network
1> {ok,Switch} = evum_switch:start().
{ok,<0.43.0>}

% Start the system console server
2> evum_ctl:start(Switch).
{ok,<0.58.0>}

% Start a Linux VM
3> {ok,R1} = evum:start().
{ok,<0.61.0>}

% And another VM ...
3> {ok,R2} = evum:start().
4ok,<0.64.0>}

% One more VM ...
5> {ok,R3} = evum:start().
{ok,<0.67.0>}

% See the Linux boot messages
6> flush().

% Set up the network interfaces
7> evum:ifconfig(R1, {"192.168.213.92","255.255.255.0","192.168.213.1"}).

8> evum:ifconfig(R2, {"192.168.213.93","255.255.255.0","192.168.213.1"}).

9> evum:ifconfig(R3, {"192.168.213.94","255.255.255.0","192.168.213.1"}).

10> evum:send(R1, "ifconfig -a").
<<"root@(none):/# ifconfig -a">>

11> flush().
Shell got <<"eth0      Link encap:Ethernet  HWaddr 00:21:5d:7c:11:11  ">>
Shell got <<"          inet addr:192.168.213.92  Bcast:192.168.213.255  Mask:255.255.255.0">>
Shell got <<"          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1">>
Shell got <<"          RX packets:0 errors:0 dropped:0 overruns:0 frame:0">>
Shell got <<"          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0">>
Shell got <<"          collisions:0 txqueuelen:1000 ">>
Shell got <<"          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)">>
Shell got <<"          Interrupt:5 ">>
Shell got <<>>
Shell got <<"lo        Link encap:Local Loopback  ">>
Shell got <<"          LOOPBACK  MTU:16436  Metric:1">>
Shell got <<"          RX packets:0 errors:0 dropped:0 overruns:0 frame:0">>
Shell got <<"          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0">>
Shell got <<"          collisions:0 txqueuelen:0 ">>
Shell got <<"          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)">>
Shell got <<>>

% Ping something, so our fake switch can learn of the VM's prescence
12> evum:ping(R1, {192,168,213,7}).
13> evum:ping(R2, {192,168,213,7}).
14> evum:ping(R3, {192,168,213,7}).

8> flush().
Shell got <<"PING 192.168.213.7 (192.168.213.7) 56(84) bytes of data.">>
Shell got <<"64 bytes from 192.168.213.7: icmp_seq=1 ttl=64 time=53.9 ms">>
Shell got <<>>
Shell got <<"--- 192.168.213.7 ping statistics ---">>
Shell got <<"1 packets transmitted, 1 received, 0% packet loss, time 0ms">>
Shell got <<"rtt min/avg/max/mdev = 53.918/53.918/53.918/0.000 ms">>

% start up a shell (of sorts) on a port
10> evum:send(R, "socat tcp-l:7777,reuseaddr,fork system:'/bin/bash',stderr &").
<<"root@(none):/# socat tcp-l:7777,reuseaddr,fork system:'/bin/bash',stderr &">>

From another host:

$ nc 192.168.213.92 7777
cat /proc/cpuinfo
processor       : 0
vendor_id       : User Mode Linux
model name      : UML
mode            : skas
host            : Linux rst 2.6.32-26-generic #48-Ubuntu SMP Wed Nov 24 09:00:03 UTC 2010 i686
bogomips        : 1468.00

SCREENSHOT: Erlang in Erlang!

root@OpenWrt:/tmp# opkg install erlang
Installing erlang (R13A-1) to root...
Downloading http://downloads.openwrt.org/backfire/10.03/x86/packages/erlang_R13A-1_x86.ipk.
Installing libncurses (5.7-2) to root...
Downloading http://downloads.openwrt.org/backfire/10.03/x86/packages/libncurses_5.7-2_x86.ipk.
Installing librt (0.9.30.1-42) to root...
Downloading http://downloads.openwrt.org/backfire/10.03/x86/packages/librt_0.9.30.1-42_x86.ipk.
Configuring libncurses.
Configuring librt.
Configuring erlang.
root@OpenWrt:/tmp# erl
Erlang R13A (erts-5.7) [source] [rq:1] [kernel-poll:false]

Eshell V5.7  (abort with ^G)
1> spawn(io, format, ["Erlang process spawned in an Erlang VM in a Linux VM in an Erlang process in an Erlang VM~n"]).
Erlang process spawned in an Erlang VM in a Linux VM in an Erlang process in an Erlang VM
<0.35.0>
2>