debian wheezy(virtualbox)에 postgresql 9.2 설치

Debian Wheezy가 포함된 virtualbox가 있습니다. Postgresql 9.2를 설치하려고 합니다. 내가 이것을 하려고 할 때이것다음 지시 사항이 있습니다.

Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 postgresql-9.2 : Depends: postgresql-common (>= 135~) but it is not going to be installed
                  Depends: ssl-cert but it is not installable
E: Unable to correct problems, you have held broken packages.

postgresql-common을 설치하려고 하면:

apt-get install postgresql-common

나는 다음 것을 얻었다:

Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 postgresql-common : Depends: ssl-cert (>= 1.0.11) but it is not installable
E: Unable to correct problems, you have held broken packages

SSL-cert를 설치하려고 하면:

apt-get install ssl-cert

나는 다음 것을 얻었다:

Reading package lists... Done
Building dependency tree
Reading state information... Done
Package ssl-cert is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'ssl-cert' has no installation candidate

저는 Linux를 처음 사용합니다. Postgresql 9.2 설치를 도와주세요.

내 것이 있어요sources.list

#

# deb cdrom:[Debian GNU/Linux 7.0.0 _Wheezy_ - Official i386 CD Binary-1 201305$

deb cdrom:[Debian GNU/Linux 7.0.0 _Wheezy_ - Official i386 CD Binary-1 20130504$

deb http://security.debian.org/ wheezy/updates main
deb-src http://security.debian.org/ wheezy/updates main

# wheezy-updates, previously known as 'volatile'
# A network mirror was not selected during install.  The following entries
# are provided as examples, but you should amend them as appropriate
# for your mirror of choice.
#
# deb http://ftp.debian.org/debian/ wheezy-updates main
# deb-src http://ftp.debian.org/debian/ wheezy-updates main