I am getting error message while installing Ubuntu 14.04 server in HP Proliant DL580 G7 server.

the error is:-

warning: The following packages cannot be authenticated 
linux-header-3.13.0-24 linux-headers-3.13.0-24-generic
linux-header-generic linux-header-server
E: there are problems and -y was used without --force-yes
base-installer:error: exiting on error base-installer/kernal/failed-install

error I am unable to install Ubuntu 14.04, i am stuck with this error

  • Are you connected to a network that has a proxy or requires authentication?
    – bain
    Jun 2, 2014 at 12:09
  • did you check the md5sum of the server install iso and the cd/flash drive ?
    – Panther
    Jun 2, 2014 at 16:26

2 Answers 2


I ran into the same problem, and found the cause was that I did not enter the "http://" prefix in the proxy setting when selecting the Ubuntu mirror. I only entered the hostname and port, e.g. "proxy.example.com:3128". Entering the full proxy URL "http://proxy.example.com:3128" worked, and the problem went away.

  • I also found that the command line apt-get is similarly finicky about the ${http_proxy} environment variable. If your http_proxy doesn't have the http:// prefix, then apt-get install will also complain about "the following packages cannot be authenticated."
    – furstex
    May 7, 2015 at 22:10

Had the same error when installing from behind a proxy server (squid3 without authentication). Connecting the machine temporarily directly to the router fixed it for me.

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