We’re doing a development-focused sprint in March 2018 to discuss features in progress and the work ahead.
Location
Budapest, Hungary
Status
Ended
Agenda
Cross-team discussions
Overview of unsupported image hacks that are in use
Snapcraft error handling
Snapcraft pack via snapd
Allow latest track to be an alias
Default track concept
Moving core18 build to foundations
API compatibility in smart local proxies
Update of kernel on Raspberry Pi
Work in progress
Application auto-start
Command not found integration
Testing in GCE
Timer services
Interface hooks
Refresh deferring commands
Gated xdg-open for files
Repairs progress
Configuration validation for core
The “system” nickname
Upcoming releases
Entitlements / Powers
Epochs
Layouts + per snap snap-update-ns profiles
User mounts + portals
Remaining work on core18
Ubuntu Core 18
Service survival across refreshes
Software watchdog support
Snapshots
Ubuntu Core 18 upgrade story
Documentation
Command snap connections
APT integration
Queuing of snapctl service commands
Work upcoming
Parallel snap installs
Hotplug
Auto-connect from the gadget
Holding refreshes while apps are running
Seccomp non-killing
Gadget snap updates
Configuration schemas
Health checks
Needs to be prepared for deployment, under discussion
Launchpad must be changed to include commands files in signed Release file
Snap store needs to send version information
Style to be tuned
Current proposals for style:
Exact matches, mixed formats
Command 'foo' not found, but can be installed as:
foorer (1.2, snap)
foomer (1.0, snap)
foozer (1.1, deb)
See 'snap info <snap name>' for additional versions.
Exact matches, only snaps available
Command 'foo' not found, but can be installed as:
foozer (1.1, snap)
foomer (1.0, snap)
See 'snap info <snap name>' for additional versions.
Exact matches, only debs available
Command 'foo' not found, but can be installed as:
foozer (1.1, deb)
foomer (1.0, deb)
Try: sudo apt install <deb name>
Fuzzy matches, mixed formats
Command 'foo' not found, did you mean:
command 'foor' from snap foorer (1.2)
command 'foor' from snap foorer (1.2)
command 'foom' from deb foomer (1.0)
command 'fooz' from deb foozer (1.1)
command 'fo' from deb foozer-somewhat-long (1.1)
See 'snap info <snap name>' for additional versions.
Fuzzy matches, only snaps available
Command 'foo' not found, did you mean:
command 'foor' from snap foorer (1.2)
command 'foor' from snap foorer (1.2)
See 'snap info <snap name>' for additional versions.
Fuzzy matches, only debs available
Command 'foo' not found, did you mean:
command 'foom' from deb foomer (1.0)
command 'fooz' from deb foozer (1.1)
command 'fo' from deb foozer-somewhat-long (1.1)
Try: sudo apt install <deb name>
There are images using arbitrary hacks in the write partition phase
Consider whether eth0 is correct as default for netplan configuration
Netplan configuration needs to be customizable for unattended installs
Some images chown /system-data/ recursively, which is a really bad practice
Most important thing to solve is social issue: open channel is needed for conversations, as no technical solution will work without a chance to replace hacks by supported methods
Add snap pack --check-skeleton doing validation before pack
Do pack in snapcraft via snap pack command
snapcraft-snap-tool built with snapd, ships /usr/lib/snapd/snap
snapcraft looks for /usr/bin/snap first, then /usr/lib/snapd/snap
snapcraft deb depends on (snapcraft-snap-tool || snapd)
snapcraft-snap-tool package must be preferred on apt install, so people that don’t have snapd won’t pull it and potentially break their environment (e.g. docker, etc); but /usr/bin/snap must be preferred by snapcraft, so that an updated snapd is used when possible
We should add support for a track to be an alias to a different track
Track aliases would be transparent to the client
Today publishers need to maintain the latest track and the latest major track manually, which is error prone
If a track is necessary for a previous major version (say, 1.0), there are good chances that there’s value in having the next major version (say, 2.0) in a track as well, so people can choose to stay in 2.0 even if 3.0 is released
Default track concept
Today the default track is the latest, always
That’s not very meaningful, as people can push whatever they want on latest
Some applications behave poorly when the client migrates from one major to the next
Epochs will help that situation, but epochs in general are about migrating the application itself. In some cases, the external users of the application (say, source code for a compiler) will stop working when the application itself is upgraded, even if the upgrade works correctly
The concept of a default track would sort that out: if snapd requests stable, unadorned with a track, the server might report back to snapd what the default track is, and that would be set as the current track, with everything else behaving the same from then on
Initial driver for the feature is holding refreshes right after seeding in some cases, but also a generally requested feature
snap refresh --hold=2h
Effective hold time is the maximum absolute time between current hold and requested hold
It does not schedule a refresh after the requested time, but instead prevents the refresh from happening within that window
Disabling the hold window is possible via --hold=none
Hold time is stored in refresh.hold core configuration setting (public)
Hold can change many times before the actual window without affecting it
At the refresh attempt, if inside a hold window, skip it as long as it doesn’t go beyond the maximum number of days (60 days right now)
Must warn if requested hold cannot be respected due to maximum period
In the future, per snap holds will be possible, but probably done via direct question to the snap (hook) instead of via persistent setting
First version of the --hold implementation will be optimistic and trust that nobody changed the configuration setting concurrently
On a follow up we’ll support configuration “nonces” (or version) that will allow optimistic locking of the configuration: “proceed as long as the config hasn’t changed since I looked”
The command work is pending, and recomputing next when inside the hold is also pending, but the underlying implementation is already up for review
Provides a way for snaps to open files in the snap filesystem
The snap runs xdg-open file://...
Request is transferred to the outside world via userd
A file descriptor is sent along with the request, and userd checks that the external path refers to the same file
A pop-up is opened to let the user decide to open the file or not
There’s a 5 minutes timeout to answer the question, after which the request is rejected by default
In the future there will be a way to make the choice sticky under some conditions
At the moment the popped up window no parent, so shows up in the middle of the screen. In the future we should be able to do better.
The implementation of xdg-open uses glib right now. That creates a dependency between snapd (the overall snap) and glib, which is a problem in a multi-base situation. We’ll port it to being a subcommand of snapctl this week.
xdg-open becomes a shell script running snapctl user-open file://...
Can we make the ubuntu core/base snaps be called something with an ubuntu prefix? The fact that we have only one store where everything lives means that once I get to having a Fedora-based core snap and Fedora base snap, I’d like to be able to configure snapd to use those on Fedora systems…
The core name is historical and doesn’t seem worth changing now. That said, note that base snaps work a bit differently than what’s suggested there. What decides the base snap to use is the snap itself, not the system it’s running on. That’s critical for the application to continue working correctly across distributions. So if a snap is installed in Fedora, it should continue using whatever core it was built with as a base. Same happens anywhere else: if a snap is built on Fedora with fedora28 (or something) as a base, and the snap is then installed in Ubuntu, snapd will pull fedora28 in and respect its base selection.
Work is being deferred as the primary requirement is gone.
Design is still looking reasonable.
We’ll focus on the full implementation later, instead of rushing it now.
Epochs
Works continues on the new store API that is a pre-requisite for epochs
Work on epochs specifically to be resumed in about a month.
Parallel installs
Will allow snaps to be installed as postgres_prod and postgres_stage, with prod and stage being local keys for the same underlying snap name.
There’s no need for any further commands to manipulate such suffixes, every command will work as usual while supporting the adorned name, as in snap install postgres_prod
Each installation has completely independent data: version, revision, track, configuration, etc.
Commands show the details in context for the given installation, as in snap info postgres_prod showing the exact revision and refresh details for that snap
The unadorned name still works, of course, with all existing semantics preserved
Bases, kernels, gadgets, will require an unadorned name to be present in the system, and that’s the one that snapd will look into for system-level activities.
The store API must get some sort of identifier for each snap (probably a sequence number) so that snapd and the store can communicate about the multiple instances. That identifier is specific to a single API call.
The suffix must be constrained so it encourages a small number of chars (probably just [a-z0-9]+), and it must not allow over 10 chars in the first implementation.
Upcoming releases
2.32 was to be released until next Monday
Bug in layouts will push out release by a week
2.33 will be difficult to ship in time for Ubuntu 18.04
Overview of unsupported image hacks that are in use
Update of kernel on Raspberry Pi