Preconfiguring packages ...
(Reading database ... 93254 files and directories currently installed.)
Preparing to unpack .../dokku_0.3.18_amd64.deb ...
Error: keyfile '/root/.ssh/id_rsa.pub' not found.
       you can enter a new keyfile path when you restart the installation.
dpkg: error processing archive /var/cache/apt/archives/dokku_0.3.18_amd64.deb (--unpack):
 subprocess new pre-installation script returned error exit status 1
Errors were encountered while processing:
 /var/cache/apt/archives/dokku_0.3.18_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@web-sites:~# 

root@web-sites:~# tail /var/log/dpkg.log 
2015-05-19 07:11:58 status unpacked sshcommand:amd64 0.0.1
2015-05-19 07:11:58 status half-configured sshcommand:amd64 0.0.1
2015-05-19 07:11:58 status installed sshcommand:amd64 0.0.1
2015-05-19 07:11:58 trigproc libc-bin:amd64 2.19-0ubuntu6.6 <none>
2015-05-19 07:11:58 status half-configured libc-bin:amd64 2.19-0ubuntu6.6
2015-05-19 07:11:58 status installed libc-bin:amd64 2.19-0ubuntu6.6
2015-05-19 07:12:00 startup archives unpack
2015-05-19 07:12:00 install dokku:amd64 <none> 0.3.18
2015-05-19 07:12:00 status half-installed dokku:amd64 0.3.18
2015-05-19 07:12:00 status not-installed dokku:amd64 <none>
root@web-sites:~#