RFC: Snappy shell

Mon Jun 15 16:42:24 UTC 2015

I'm personally two-hearted about this idea.

On one hand, I can see the appeal, and have used something similar to that
myself for Smart Package Manager, where people could use a shell to type in
the all of the subcommands that they could use under the "smart" command
line tool. It was a neat way to type several subcommands in a row without
the cost of initializing the in-memory graph cache necessary for computing
operations, and was expensive to do.

On the other hand, there's no relevant init cost for the snappy cli, and
custom shell can become an annoyance rather than an advantage. For example,
I use traditional unix tools such as grep, sed, awk, sort, all the time
when interacting with textual output from dpkg, apt, etc, and also use text
files as temporary storage, shell variables, etc. Being in a custom shell
means people will be constrained in an unusual way within an atypical shell
to the tasks which they tend to understand otherwise.

The thing that fired my worries while reading your message was the part
where you say the goal is to deliver a slick console user experience as
found when telneting into network equipment. While I don't have much
experience there, the few times I did that I found myself within an alien
and apparently clumsy environment where I'd have to re-learn everything. It
wasn't a smooth feeling at all.

So, here is an idea: rather than redoing the whole shell, can we identify
what are the winning aspects of that integrated shell (good help? pleasant
command names? etc) and try to replicate that within a traditional shell?

On Mon, Jun 15, 2015 at 12:50 PM, Loïc Minier <loic.minier at ubuntu.com>
wrote:

> User experience
>
> When you SSH into a Snappy system, you currently end up on a shell prompt.
> Wouldn’t it be great to actually land in Snappy itself?
>
> Welcome to Snappy Ubuntu Core 15.04
>
> snappy#
>
> How do I get started?
>
> snappy# help
>
> Usage:
>
>  <command> [<arg>...]
>
> Available commands
>
>  booted              Flag that rootfs booted successfully
>
>  build               Builds a snap package (aliases: bu)
>
>  config              Set configuration for an installed package.
>
> [... edited for brievety...]
>
>  shell               Start a shell
>
>  update              Update all installed parts
>
>  versions            (deprecated) please use "list"
>
> Simple commands like install, update etc. work as expected:
>
> snappy# info
>
> release: ubuntu-core/15.04/stable
>
> architecture: amd64
>
> frameworks: webdm
>
> apps:
>
> snappy# list -v
>
> Name          Date       Version Developer
>
> ubuntu-core   2015-06-11 3       ubuntu*
>
> webdm         2015-06-11 0.9     *
>
> generic-amd64 2015-06-11 1.1.1   *
>
> We should revisit some commands or aliases to have a friendlier, more
> rewarding user experience, e.g. update could provide some output when no
> update is available and entering a shell command like ls would hint at
> using help:
>
> snappy# update
>
> System is up-to-date!
>
> snappy# ls
>
> No such command; “help” for a list of commands
>
> Configuration is only possible for snaps that have the required hook and
> may be set manually by key or globally from an URL, and of course immutable
> configs can’t be changed.
>
> snappy# config
>
> (config)# list
>
> Name           Date       Version Developer
>
> ubuntu-core    2015-06-11 3       ubuntu
>
> config-example 2015-06-15 1.0.6   canonical
>
> webdm          2015-06-11 0.9
>
> (config)# config xkcd-webserver
>
> No config found for this snap
>
> (config)# config ubuntu-core
>
> (ubuntu-core)# show
>
> autopilot: true
>
> timezone: Etc/UTC
>
> hostname: localhost.localdomain
>
> (ubuntu-core)# set autopilot false
>
> Config set
>
> (ubuntu-core)# exit
>
> snappy# config config-example set -u
> https://conf.example.com/config-example.yaml
>
> Config set
>
> A new shell command is provided to start the default user’s interactive
> shell or to run commands ( under “sh -c”).
>
> Goals of snappy shell
>
>
>    -
>
>    Deliver a slick console user experience as found when SSH-ing (or
>    telnet-ing) into network equipments such as switches, routers, firewalls
>    etc.
>    -
>
>    Allows restricting access to the shell while allowing for useful
>    features such as update, install etc. (could be controlled by a new
>    allowed-cli-commands ubuntu-core config or similar)
>    -
>
>    Smoothes transition into a Comfy world where the regular rootfs
>    becomes smaller and smaller.
>
>
> Implementation
>
> This user experience would be delivered by the main “snappy” binary when
> it’s launched as “snappy-cli” as the basename of argv[0]. If this feature
> is not enabled by default, or from a shell, you would run “snappy cli” to
> start an interactive snappy shell session. NB: cli is to avoid confusion
> with the shell command to run a command or an interactive shell.
>
> SSH integration could be done in multiple ways:
>
>    1.
>
>    integrate a SSH server in snappy itself; I don’t know how hard this is
>    in go today; this might be a worthwhile exercise long-term to get a smaller
>    rootfs
>    2.
>
>    configure SSH server and login to always start /bin/snappy-cli instead
>    of the user’s shell, then lookup the user’s shell in the passwd
>    database to run the preferred shell with “snappy shell”
>    3.
>
>    (preferred) configure the user’s shell to /bin/snappy-cli and create a
>    new snappy-only ubuntu-core config for the preferred interactive shell
>    (defaults to /bin/bash); drawback: this would be system-wide as we
>    don’t have per-user configs
>
>
> Questions? Comments? Pile on at:
> https://docs.google.com/document/d/1DeR2JoCBDX2C1r6a2wV60uqvi7a89OwHh5gJ19tBZvM/edit
>
> Cheers,
> --
> Loïc Minier
>
> --
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>

-- 
gustavo @ http://niemeyer.net
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