If you have some problems with package updates and apt-get return the message ‘The following packages have been kept back’ means that the packages have been retained and there are newer versions of the listed packages, which for some reason cannot be installed. (unfulfilled or changed or new dependencies)

The solution:

apt-get dist-upgrade -u

Example:

root@main:~# apachectl -v

Server version: Apache/2.4.10 (Debian)

Server built:   Jul 18 2017 18:32:16

root@main:~# apt-get update

Ign:1 http://mirror.nl.leaseweb.net/debian stretch InRelease

Get:2 http://security.debian.org/debian-security stretch/updates InRelease [63.0 kB]

Get:3 http://mirror.nl.leaseweb.net/debian stretch-updates InRelease [91.0 kB]

Hit:4 http://mirror.nl.leaseweb.net/debian stretch Release

Get:5 http://repo.percona.com/apt stretch InRelease [15.8 kB]

Fetched 170 kB in 0s (506 kB/s)

Reading package lists... Done
root@main:~# apt-get upgrade

Reading package lists... Done

Building dependency tree

Reading state information... Done

Calculating upgrade... Done

The following packages have been kept back:

  apache2 apache2-bin apache2-data libgd3 linux-image-amd64

0 upgraded, 0 newly installed, 0 to remove and 5 not upgraded.
root@main:~# apt-get dist-upgrade -u

Reading package lists... Done

Building dependency tree

Reading state information... Done

Calculating upgrade... Done

The following NEW packages will be installed:

  firmware-linux-free irqbalance libglib2.0-0 libglib2.0-data liblua5.2-0 libwebp6 linux-image-4.9.0-4-amd64 shared-mime-info xdg-user-dirs

The following packages will be upgraded:

  apache2 apache2-bin apache2-data libgd3 linux-image-amd64

5 upgraded, 9 newly installed, 0 to remove and 0 not upgraded.

Need to get 46.9 MB of archives.

After this operation, 211 MB of additional disk space will be used.

Do you want to continue? [Y/n] y

......
root@main:~# apachectl -v

Server version: Apache/2.4.25 (Debian)

Server built:   2017-09-19T18:58:57