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https://github.com/t184256/fingertip

Control VMs, containers and other machines with Python, leverage live snapshots
https://github.com/t184256/fingertip

Last synced: 21 days ago
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Control VMs, containers and other machines with Python, leverage live snapshots

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README 

        
`fingertip`

-----------



This program/library aims to be a way to:



* fire up VMs and containers in mere seconds using live VM snapshots

* uniformly control machines from Python by writing small and neat functions

  transforming them

* compose and transparently cache the results of these functions

* build cool apps that exploit live VM snapshots and checkpoints

* control other types of machines that are not local VMs



All while striving to be intentionally underengineered

and imposing as few limits as possible.

If you look at it and think that it does nothing in the laziest way possible,

that's it.



It's currently in alpha stage.



# Teaser



Some examples of executing it from your shell:



``` bash

$ fingertip os.fedora + ssh  # install Fedora and SSH into it

$ fingertip os.alpine + console  # install Alpine, access serial console

$ fingertip os.alpine + ansible package --state=present --name=patch + ssh

$ fingertip backend.podman-criu + os.alpine + console  # containers!

$ fingertip os.fedora + script.debug myscript.sh  # checkpoint-powered debugger

```



An example of Python usage and writing your own steps:



``` python

import fingertip



def main(m=None, alias='itself'):

    m = m or fingertip.build('os.fedora')

    m = m.apply('ansible', 'lineinfile', path='/etc/hosts',

                line=f'127.0.0.1 {alias}')

    with m:

        assert '1 received' in m(f'ping -c1 {alias}').out

    return m

```



Put in `fingertip/plugins/demo.py`,

this can be now be used in pipelines:

```

$ fingertip demo

$ fingertip os.fedora + demo me

$ fingertip os.alpine + demo --alias=myself + ssh

```



## Installation



Refer to [INSTALL.md](INSTALL.md).



### Shell usage



If you have installed fingertip, invoke it as `fingertip`.



If you're running from a checkout, use `python3 ` instead

or make an alias.



If you're using a containerized version, invoke `fingertip-containerized`

(and hope for the best).



So,



``` bash

$ fingertip os.fedora + ssh

```



You should observe Fedora installation starting up,

then shutting down, booting up again and, finally,

giving you interactive control over the machine over SSH.



Invoke the same command again, and it should do nearly nothing, as

the downloads and the installation are already cached

in `~/.cache/fingertip`.

Enjoy fresh clean VMs brought up in mere seconds.

Feel like they're already at your fingertips.

Control them from console or from Python.



## Python usage



Let's see how manipulating machines can look like

(`fingertip/plugins/self_test/greeting.py`):



``` python

def make_greeting(m, greeting='Hello!'):                      # take a machine

    with m:                                                   # start if needed

        m.console.sendline(f"echo '{greeting}' > .greeting")  # type a command

        m.console.expect_exact(m.prompt)                      # wait for prompt

    return m                                                  # cache result



@fingertip.transient                                          # don't lock/save

def main(m, greeting='Hello!'):                               # take a machine

    m = m.apply(make_greeting, greeting=greeting)             # use cached step

    with m:                                                   # start if needed

        assert m('cat .greeting').out.strip() == greeting     # execute command

                                                              # do not save

```



Plugins are regular Python functions, nothing fancy.

You can just pass them `fingertip.build('fedora')` and that'll work.

Even this `@fingertip.transient` thing

is just an optimization hint to `.apply()`.



Here's what can happen inside such a function:



* It accepts a machine as the first argument

  (which may be already spun up or not, you don't know).

* It inspects it and applies more functions if it wants to,

  (extra steps applied through `.apply` are cached / reused if it's possible).

* Should any custom steps or changes be applied,

  the machine must be first spun up using a `with` block (`with m as m`).

  All modifications to the machine must happen inside that block,

  or risk being silently undone!

* Return the machine if the result should be cached and used for the next steps.

  Not returning one can and usually will undo all the changes you've made.

  If you don't intend to save the result, don't return m;

  additionally, decorate the function with `@fingertip.transient`

  so that fingertip can apply performance optimizations and avoid locking.

  There's much more to it, see `docs/on_transiency.md` for details.



The first function in the chain (or the one used in `fingertip.build`)

will not get a machine as the first argument.

To write a universal function, just use:

``` python

def func(m=None):

    m = m or fingertip.build('fedora')

    ...

```



## Disclaimer



Due to what exactly I cache and the early stage of development,

empty your `~/.cache/fingertip/machines` often, at least after each update.



``` bash

$ fingertip cleanup machines all

```



Some days the whole `~/.cache/fingertip` has to go.



``` bash

$ fingertip cleanup everything

```