[FFE] 'netplan try' feature in netplan 0.35

[Mathieu Trudel-Lapierre]

netplan 0.35 would include an additional command:

 netplan try

This would be used to allow users to automatically attempt to apply any config that can be safely programmatically revert in the case of failure, and presenting the user with a prompt to acknowledge the changes. The prompt is intended as a way to ensure the user still has access to the system when the settings are applied. In the event the user can't approve the changes, they are backed out after a timeout (120 seconds by default to give the network time to converge).

Settings that can't be backed out are limited to custom bridge and bond settings that tweak behavior of these devices, since networkd does not necessarily update these settings when bond devices are changed (only when they are being created).

'netplan try' is already available as a separate tree in git:
https://github.com/CanonicalLtd/netplan/pull/15/files

This FFE is to make sure the community is aware of these changes so late in the cycle, and to ensure those are acceptable to land right now, being leaf changes, fully covered by unit tests and autopkgtests (along with manual testing). Only users consciously making the decision to use the command would run into this code path.

The changes are limited to some terminal mangling to allow for the prompt and timeout; everything else is handled directly in the existing 'netplan apply' code with minimal change to allow this code to be executed from another "command".

This FFE request seeks pre-approval before merging the "try-command" branch that incldues this new feature into netplan master to proceed with the release of netplan 0.35.

[Steve Langasek (vorlon)]

Standalone feature with no impact on the rest of the software or the OS. FFe approved.

[Launchpad Janitor (janitor)]

This bug was fixed in the package netplan.io - 0.35

---------------
netplan.io (0.35) bionic; urgency=medium

  * debian/postinst: fix version check for when to write breadcrumbs.
    (LP: #1756742)
  * bonds/bridges: Support specifying time-based values with "ms" suffix when
    the value should be in milliseconds; while keeping support for the previous
    behavior of handling values are pure seconds when no suffix is present.
    (LP: #1745597)
  * IPv6: accept-ra should default to being unset, so that the kernel default
    can be used. (LP: #1732002)
  * DHCPv4: add a "dhcp-identifier: mac" field that can be set to fix interop
    with Windows Server-based DHCP servers which don't support RFC 4361.
    (LP: #1738998)
  * docs, examples: reformat comments in examples, add standalone example files
  * debian/docs, debian/netplan.io.install: install doc and examples in the
    right locations.
  * netplan try: allow users to preview/test and approve network configuration
    changes, and automatically revert if they are not accepted. (LP: #1764824)
  * networkd: don't wipe out /run/netplan on generate: we do want to keep any
    YAML configurations in that directory, we just need to remove generated
    wpasupplicant configs. (LP: #1764869)
  * debian/control: add bash-completion to Build-Depends to make sure we do
    install completion files in the right location.

 -- Mathieu Trudel-Lapierre <email address hidden> Tue, 17 Apr 2018 21:49:21 -0400