Что означает неопределенные зависимости?

Question 1

Мне нужно установить php5-xmlrpc, но я вижу этот результат:

apt-get install php5-xmlrpc --fix-missing
.
.
.

The following packages have unmet dependencies:
php5-xmlrpc : Depends: php5-common (= 5.6.4+dfsg-4ubuntu6.4) but 5.6.11+dfsg-1ubuntu3.4 is to be installed
E: Unable to correct problems, you have held broken packages.

php5-xmlrpc

## Note, this file is written by cloud-init on first boot of an instance
## modifications made here will not survive a re-bundle.
## if you wish to make changes you can:
## a.) add 'apt_preserve_sources_list: true' to /etc/cloud/cloud.cfg
##     or do the same in user-data
## b.) add sources in /etc/apt/sources.list.d
## c.) make changes to template file /etc/cloud/templates/sources.list.tmpl

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid main
deb-src http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid main

## Major bug fix updates produced after the final release of the
## distribution.
deb http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid-updates main
deb-src http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid-updates main

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid universe
deb-src http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid universe
deb http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid-updates universe
deb-src http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
# deb http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid multiverse
# deb-src http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid multiverse
# deb http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid-updates multiverse
# deb-src http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid-updates multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid-backports main restricted universe multiverse
# deb-src http://us-central1.gce.archive.ubuntu.com/ubuntu/ vivid-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu vivid partner
# deb-src http://archive.canonical.com/ubuntu vivid partner

deb http://security.ubuntu.com/ubuntu vivid-security main
deb-src http://security.ubuntu.com/ubuntu vivid-security main
deb http://security.ubuntu.com/ubuntu vivid-security universe
deb-src http://security.ubuntu.com/ubuntu vivid-security universe
# deb http://security.ubuntu.com/ubuntu vivid-security multiverse
# deb-src http://security.ubuntu.com/ubuntu vivid-security multiverse

Question 2

Неудовлетворенные зависимости означают, что пакет, который вы пытаетесь установить, требует определенного пакета, но apt не может его найти.