apt-get and apt-cache

These commands can be substituted by the newer, apt, command which uses these commands.

Package Info

In order to obtain information about a package which is available on your system you have to know the name of the package eg mysql-server not mysql. If we try with the wrong name or the correct name of a package but one which is not on our system:

package does not exist

steve@steve-Inspiron-3268:~$ apt-cache policy mysql
N: Unable to locate package mysql

Now for a package that does exist:

package does exist

steve@steve-Inspiron-3268:~$ apt-cache policy mysql-server
mysql-server:
  Installed: (none)
  Candidate: 8.0.31-0ubuntu0.22.04.1
  Version table:
     8.0.31-0ubuntu0.22.04.1 500
        500 http://gb.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        500 http://gb.archive.ubuntu.com/ubuntu jammy-updates/main i386 Packages
        500 http://security.ubuntu.com/ubuntu jammy-security/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu jammy-security/main i386 Packages
     8.0.28-0ubuntu4 500
        500 http://gb.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
        500 http://gb.archive.ubuntu.com/ubuntu jammy/main i386 Packages