mount: mounting /dev/sda on /cdrom failed: Invalid argument
stdin: Not a typewriter
Generating locales...
  en_US.UTF-8... done
Generation complete.
pwconv: failed to change the mode of /etc/passwd- to 0600
Using CD-ROM mount point /cdrom/
Identifying... [936b9526c88714b6af2fc858d5b8504b-2]
Scanning disc for index files...
Found 2 package indexes, 0 source indexes, 0 translation indexes and 1 signatures
Found label 'Ubuntu 15.04 _Vivid Vervet_ - Alpha amd64 (20141201)'
This disc is called: 
'Ubuntu 15.04 _Vivid Vervet_ - Alpha amd64 (20141201)'
Copying package lists...gpgv: Signature made Mon Dec  1 08:35:32 2014 UTC using DSA key ID FBB75451
gpgv: Good signature from "Ubuntu CD Image Automatic Signing Key <cdimage@ubuntu.com>"

Reading Package Indexes... 0%

Reading Package Indexes... Done
Writing new source list
Source list entries for this disc are:
deb cdrom:[Ubuntu 15.04 _Vivid Vervet_ - Alpha amd64 (20141201)]/ vivid main restricted
Repeat this process for the rest of the CDs in your set.