After upgrading to Linux Mint 21, I am puzzled by some held back packages, one of which is apt:

# apt-cache policy apt

  Installed: 2.4.6
  Candidate: 2.4.7
  Version table:
     2.4.7 500 (phased 20%)
        500 http://archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
 *** 2.4.6 100
        100 /var/lib/dpkg/status
     2.4.5 500
        500 http://archive.ubuntu.com/ubuntu jammy/main amd64 Packages

Could anyone elaborate, thank you?

apt-get upgrade trial below:

# apt-get upgrade

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
  apt apt-transport-https apt-utils cryptsetup cryptsetup-bin cryptsetup-initramfs
  cryptsetup-run libapt-pkg6.0 libcryptsetup12
0 upgraded, 0 newly installed, 0 to remove and 9 not upgraded.

1 Answer 1


Phased updates are updates which should only be applied by a subset of all systems running a given release of a distribution; this allows updates to be rolled out progressively.

This feature was introduced by this commit and is documented as follows:

Phased Updates

APT understands a field called Phased-Update-Percentage which can be used to control the rollout of a new version. It is an integer between 0 and 100.

A system's eligibility to a phased update is determined by seeding random number generator with the package source name, the version number, and /etc/machine-id, and then calculating an integer in the range [0, 100]. If this integer is larger than the Phased-Update-Percentage, the version is pinned to 1, and thus held back. Otherwise, normal policy rules apply.

In case you have multiple systems that you want to receive the same set of updates, you can set APT::Machine-ID to a UUID such that they all phase the same, or set APT::Get::Never-Include-Phased-Updates or APT::Get::Always-Include-Phased-Updates to true such that APT will never/always consider phased updates.

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