Ubuntu Snapshot Service

The Ubuntu snapshot service makes it possible to see and use the Ubuntu archive as it was at any specified date and time. Snapshots of the Ubuntu archive are available for any date and time after 1 March 2023. This means that you are able to enable the service on the repositories and use apt to query or install packages as they were at any recent date and time.

Common use cases of this service include:

  • enabling reproducible deployments of a set of packages as at a particular date and time;
  • determining when a change in behaviour occurred in the archive; and
  • supporting a structured update workflow, for example where a snapshot is validated in
    one environment before being released to other environments.

Snapshots are supported in Ubuntu 23.10 onwards, plus on updated installations of Ubuntu 20.04 LTS (apt 2.0.10) and Ubuntu 22.04 LTS (apt 2.4.11). We intend to ensure snapshots are available for dates up to at least 2 years in the past, which we may extend if there is demand.

Quick-Start Example

On Ubuntu 24.04 LTS and later, installing the version of hello as it was at 3:04:00 am UTC on 1 March 2024 is as simple as using the following command (on an instance that does not already have hello installed):

apt install hello --update --snapshot 20240301T030400Z

This command first updates your package indexes (the --update argument is the equivalent of running apt update before the specified apt command) and then installs the hello package from the specified snapshot instead of the latest version in the archive. In the output, you should see that the package is being downloaded from the snapshot server:

Get:1 https://snapshot.ubuntu.com/ubuntu/20240301T030400Z noble/main
amd64 hello amd64 2.10-3 [26.2 kB]

How to Use Snapshots on Ubuntu

Enable snapshot service on configured repositories

For Ubuntu 24.04 and later

The apt included in Ubuntu 24.04 and later automatically detects when snapshots are supported for a repository (any repository with a Snapshots: directive in the Release file). This includes the official Ubuntu repositories, so snapshots for these will be enabled by default.

For Ubuntu 23.10 and earlier

On Ubuntu 23.10 and earlier, edit /etc/apt/sources.list to add [snapshot=yes] into the standard prefix, for example:

deb [snapshot=yes] http://archive.ubuntu.com/ubuntu/ jammy main restricted
deb [snapshot=yes] http://archive.ubuntu.com/ubuntu/ jammy-updates main restricted
deb [snapshot=yes] http://security.ubuntu.com/ubuntu jammy-security main restricted

Use a Snapshot ID with apt Commands

Snapshot ID format

The Snapshot ID will be the desired date and UTC time in the YYYYMMDDTHHMMSSZ format, for example 20230302T030400Z for 03:04 UTC on 2 March 2023.

Using a Snapshot ID with each apt command

Once snapshots are enabled for a repository, it is possible to pass a specific Snapshot ID to most apt or apt-get commands with --snapshot [Snapshot ID] or -S [Snapshot ID], for example:

apt update --snapshot 20231102T030400Z
apt policy hello -S 20231102T030400Z
apt install hello --snapshot 20231102T030400Z

Note that the apt update --snapshot [snapshot] command needs to be run immediately before the other apt commands. These commands will also fail if the snapshot format is incorrect or the snapshot does not exist (for example, if you try to use a date before that Ubuntu release existed).

Using a specific snapshot for a repository for all apt commands

Enabling snapshots for the repository will allow you to specify a snapshot when using apt, as shown above. Alternatively, it is possible to set apt to use a particular snapshot for all apt commands for a repository, including unattended-upgrades. To do this, the specific Snapshot ID (e.g. 20230302T030400Z) can be used in the place of “yes” in the relevant source. If a specific snapshot is configured in this way then it will be used even if a different snapshot ID is given as part of an apt command.

For example, on Ubuntu 24.04 LTS onwards:

Types: deb
URIs: http://archive.ubuntu.com/ubuntu
Suites: noble noble-updates
Components: main universe
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
Snapshot: 20240301T030400Z

## Ubuntu security updates. Aside from URIs and Suites,
## this should mirror your choices in the previous section.
Types: deb
URIs: http://security.ubuntu.com/ubuntu
Suites: noble-security
Components: main universe
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
Snapshot: 20240301T030400Z

Ubuntu 23.10 and earlier:

deb [snapshot=20230302T030400Z] http://archive.ubuntu.com/ubuntu/ jammy main restricted
deb [snapshot=20230302T030400Z] http://archive.ubuntu.com/ubuntu/ jammy-updates main restricted
deb [snapshot=20230302T030400Z] http://security.ubuntu.com/ubuntu jammy-security main restricted

Using a specific snapshot for all repositories that support snapshots

Alternatively, across all supported Ubuntu releases, a snapshot can be set for all repositories that have snapshots enabled on a system using an apt.confa variable. First, ensure the relevant repositories are enabled, and then set APT::Snapshot to the relevant snapshot ID, for example:

echo 'APT::Snapshot "20240301T030400Z";' | sudo tee /etc/apt/apt.conf.d/50snapshot

As above, this snapshot will then be used for all apt commands, including unattended-upgrades. The system can then be updated to use a different snapshot by simply running the above command again with a different snapshot ID.

Disable Snapshot Service for a repository

For Ubuntu 24.04 and later (Deb822 sources)

As mentioned above, on Ubuntu 24.04 and later, snapshots are enabled automatically for supported repositories. If you do not want archive snapshots to be enabled for a repository, edit the relevant sources file (e.g. /etc/apt/sources.list.d/ubuntu.sources) to add Snapshot: no to the relevant sources, for example:

Types: deb
URIs: http://archive.ubuntu.com/ubuntu
Suites: noble noble-updates
Components: main universe
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
Snapshot: no

For Ubuntu 23.10 and earlier

On Ubuntu 23.10 and earlier the included version of apt did not automatically detect snapshot support and so snapshots should not be enabled unless you have added [snapshot=yes] to the relevant source (as explained above).

See Also