root@Anubis:~# apt-get install arachni
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
arachni
0 upgraded, 1 newly installed, 0 to remove and 59 not upgraded.
Need to get 0 B/1,766 kB of archives.
After this operation, 7,903 kB of additional disk space will be used.
Selecting previously unselected package arachni.
(Reading database ... 318464 files and directories currently installed.)
Preparing to unpack .../arachni_1.4-0kali1_all.deb ...
Unpacking arachni (1.4-0kali1) ...
Setting up arachni (1.4-0kali1) ...
root@Anubis:~# arachni
/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in require': cannot load such file -- msgpack/msgpack (LoadError) from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:inrequire'
from /usr/lib/ruby/vendor_ruby/msgpack.rb:11:in rescue in <top (required)>' from /usr/lib/ruby/vendor_ruby/msgpack.rb:8:in<top (required)>'
from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in require' from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:inrequire'
from /usr/share/arachni/lib/arachni/rpc/serializer.rb:9:in <top (required)>' from /usr/share/arachni/lib/arachni/report.rb:9:inrequire_relative'
from /usr/share/arachni/lib/arachni/report.rb:9:in <top (required)>' from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:inrequire'
from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in require' from /usr/share/arachni/lib/arachni/framework.rb:35:in<module:Arachni>'
from /usr/share/arachni/lib/arachni/framework.rb:17:in <top (required)>' from /usr/share/arachni/lib/arachni.rb:103:inrequire_relative'
from /usr/share/arachni/lib/arachni.rb:103:in <top (required)>' from /usr/share/arachni/ui/cli/framework.rb:9:inrequire_relative'
from /usr/share/arachni/ui/cli/framework.rb:9:in <top (required)>' from ./arachni:10:inrequire_relative'
from ./arachni:10:in `<main>'