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#mgmt
<!--
Mgmt
Copyright (C) 2013-2016+ James Shubin and the project contributors
Written by James Shubin <james@shubin.ca> and the project contributors
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
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##mgmt by [James](https://ttboj.wordpress.com/)
####Available from:
####[https://github.com/purpleidea/mgmt/](https://github.com/purpleidea/mgmt/)
####This documentation is available in: [Markdown](https://github.com/purpleidea/mgmt/blob/master/DOCUMENTATION.md) or [PDF](https://pdfdoc-purpleidea.rhcloud.com/pdf/https://github.com/purpleidea/mgmt/blob/master/DOCUMENTATION.md) format.
####Table of Contents
1. [Overview](#overview)
2. [Project description - What the project does](#project-description)
3. [Setup - Getting started with mgmt](#setup)
4. [Features - All things mgmt can do](#features)
* [Autoedges - Automatic resource relationships](#autoedges)
* [Autogrouping - Automatic resource grouping](#autogrouping)
* [Automatic clustering - Automatic cluster management](#automatic-clustering)
* [Remote mode - Remote "agent-less" execution](#remote-agent-less-mode)
5. [Usage/FAQ - Notes on usage and frequently asked questions](#usage-and-frequently-asked-questions)
6. [Reference - Detailed reference](#reference)
* [Graph definition file](#graph-definition-file)
* [Command line](#command-line)
7. [Examples - Example configurations](#examples)
8. [Development - Background on module development and reporting bugs](#development)
9. [Authors - Authors and contact information](#authors)
##Overview
The `mgmt` tool is a next generation config management prototype. It's not yet
ready for production, but we hope to get there soon. Get involved today!
##Project Description
The mgmt tool is a distributed, event driven, config management tool, that
supports parallel execution, and librarification to be used as the management
foundation in and for, new and existing software.
For more information, you may like to read some blog posts from the author:
* [Next generation config mgmt](https://ttboj.wordpress.com/2016/01/18/next-generation-configuration-mgmt/)
* [Automatic edges in mgmt](https://ttboj.wordpress.com/2016/03/14/automatic-edges-in-mgmt/)
* [Automatic grouping in mgmt](https://ttboj.wordpress.com/2016/03/30/automatic-grouping-in-mgmt/)
* [Automatic clustering in mgmt](https://ttboj.wordpress.com/2016/06/20/automatic-clustering-in-mgmt/)
There is also an [introductory video](http://meetings-archive.debian.net/pub/debian-meetings/2016/debconf16/Next_Generation_Config_Mgmt.webm) available.
Older videos and other material [is available](https://github.com/purpleidea/mgmt/#on-the-web).
##Setup
During this prototype phase, the tool can be run out of the source directory.
You'll probably want to use ```./run.sh run --file examples/graph1.yaml``` to
get started. Beware that this _can_ cause data loss. Understand what you're
doing first, or perform these actions in a virtual environment such as the one
provided by [Oh-My-Vagrant](https://github.com/purpleidea/oh-my-vagrant).
##Features
This section details the numerous features of mgmt and some caveats you might
need to be aware of.
###Autoedges
Automatic edges, or AutoEdges, is the mechanism in mgmt by which it will
automatically create dependencies for you between resources. For example,
since mgmt can discover which files are installed by a package it will
automatically ensure that any file resource you declare that matches a
file installed by your package resource will only be processed after the
package is installed.
####Controlling autoedges
Though autoedges is likely to be very helpful and avoid you having to declare
all dependencies explicitly, there are cases where this behaviour is
undesirable.
Some distributions allow package installations to automatically start the
service they ship. This can be problematic in the case of packages like MySQL
as there are configuration options that need to be set before MySQL is ever
started for the first time (or you'll need to wipe the data directory). In
order to handle this situation you can disable autoedges per resource and
explicitly declare that you want `my.cnf` to be written to disk before the
installation of the `mysql-server` package.
You can disable autoedges for a resource by setting the `autoedge` key on
the meta attributes of that resource to `false`.
####Blog post
You can read the introductory blog post about this topic here:
[https://ttboj.wordpress.com/2016/03/14/automatic-edges-in-mgmt/](https://ttboj.wordpress.com/2016/03/14/automatic-edges-in-mgmt/)
###Autogrouping
Automatic grouping or AutoGroup is the mechanism in mgmt by which it will
automatically group multiple resource vertices into a single one. This is
particularly useful for grouping multiple package resources into a single
resource, since the multiple installations can happen together in a single
transaction, which saves a lot of time because package resources typically have
a large fixed cost to running (downloading and verifying the package repo) and
if they are grouped they share this fixed cost. This grouping feature can be
used for other use cases too.
You can disable autogrouping for a resource by setting the `autogroup` key on
the meta attributes of that resource to `false`.
####Blog post
You can read the introductory blog post about this topic here:
[https://ttboj.wordpress.com/2016/03/30/automatic-grouping-in-mgmt/](https://ttboj.wordpress.com/2016/03/30/automatic-grouping-in-mgmt/)
###Automatic clustering
Automatic clustering is a feature by which mgmt automatically builds, scales,
and manages the embedded etcd cluster which is compiled into mgmt itself. It is
quite helpful for rapidly bootstrapping clusters and avoiding the extra work to
setup etcd.
If you prefer to avoid this feature. you can always opt to use an existing etcd
cluster that is managed separately from mgmt by pointing your mgmt agents at it
with the `--seeds` variable.
####Blog post
You can read the introductory blog post about this topic here:
[https://ttboj.wordpress.com/2016/06/20/automatic-clustering-in-mgmt/](https://ttboj.wordpress.com/2016/06/20/automatic-clustering-in-mgmt/)
###Remote ("agent-less") mode
Remote mode is a special mode that lets you kick off mgmt runs on one or more
remote machines which are only accessible via SSH. In this mode the initiating
host connects over SSH, copies over the `mgmt` binary, opens an SSH tunnel, and
runs the remote program while simultaneously passing the etcd traffic back
through the tunnel so that the initiators etcd cluster can be used to exchange
resource data.
The interesting benefit of this architecture is that multiple hosts which can't
connect directly use the initiator to pass the important traffic through to each
other. Once the cluster has converged all the remote programs can shutdown
leaving no residual agent.
This mode can also be useful for bootstrapping a new host where you'd like to
have the service run continuously and as part of an mgmt cluster normally.
In particular, when combined with the `--converged-timeout` parameter, the
entire set of running mgmt agents will need to all simultaneously converge for
the group to exit. This is particularly useful for bootstrapping new clusters
which need to exchange information that is only available at run time.
####Blog post
An introductory blog post about this topic will follow soon.
##Usage and frequently asked questions
(Send your questions as a patch to this FAQ! I'll review it, merge it, and
respond by commit with the answer.)
###Why did you start this project?
I wanted a next generation config management solution that didn't have all of
the design flaws or limitations that the current generation of tools do, and no
tool existed!
###Why did you use etcd? What about consul?
Etcd and consul are both written in golang, which made them the top two
contenders for my prototype. Ultimately a choice had to be made, and etcd was
chosen, but it was also somewhat arbitrary. If there is available interest,
good reasoning, *and* patches, then we would consider either switching or
supporting both, but this is not a high priority at this time.
###Can I use an existing etcd cluster instead of the automatic embedded servers?
Yes, it's possible to use an existing etcd cluster instead of the automatic,
elastic embedded etcd servers. To do so, simply point to the cluster with the
`--seeds` variable, the same way you would if you were seeding a new member to
an existing mgmt cluster.
The downside to this approach is that you won't benefit from the automatic
elastic nature of the embedded etcd servers, and that you're responsible if you
accidentally break your etcd cluster, or if you use an unsupported version.
###What does the error message about an inconsistent dataDir mean?
If you get an error message similar to:
```
Etcd: Connect: CtxError...
Etcd: CtxError: Reason: CtxDelayErr(5s): No endpoints available yet!
Etcd: Connect: Endpoints: []
Etcd: The dataDir (/var/lib/mgmt/etcd) might be inconsistent or corrupt.
```
This happens when there are a series of fatal connect errors in a row. This can
happen when you start `mgmt` using a dataDir that doesn't correspond to the
current cluster view. As a result, the embedded etcd server never finishes
starting up, and as a result, a default endpoint never gets added. The solution
is to either reconcile the mistake, and if there is no important data saved, you
can remove the etcd dataDir. This is typically `/var/lib/mgmt/etcd/member/`.
###Why do resources have both a `Compare` method and an `IFF` (on the UUID) method?
The `Compare()` methods are for determining if two resources are effectively the
same, which is used to make graph change delta's efficient. This is when we want
to change from the current running graph to a new graph, but preserve the common
vertices. Since we want to make this process efficient, we only update the parts
that are different, and leave everything else alone. This `Compare()` method can
tell us if two resources are the same.
The `IFF()` method is part of the whole UUID system, which is for discerning if
a resource meets the requirements another expects for an automatic edge. This is
because the automatic edge system assumes a unified UUID pattern to test for
equality. In the future it might be helpful or sane to merge the two similar
comparison functions although for now they are separate because they are
actually answer different questions.
###Did you know that there is a band named `MGMT`?
I didn't realize this when naming the project, and it is accidental. After much
anguishing, I chose the name because it was short and I thought it was
appropriately descriptive. If you need a less ambiguous search term or phrase,
you can try using `mgmtconfig` or `mgmt config`.
###You didn't answer my question, or I have a question!
It's best to ask on [IRC](https://webchat.freenode.net/?channels=#mgmtconfig)
to see if someone can help you. Once we get a big enough community going, we'll
add a mailing list. If you don't get any response from the above, you can
contact me through my [technical blog](https://ttboj.wordpress.com/contact/)
and I'll do my best to help. If you have a good question, please add it as a
patch to this documentation. I'll merge your question, and add a patch with the
answer!
##Reference
Please note that there are a number of undocumented options. For more
information on these options, please view the source at:
[https://github.com/purpleidea/mgmt/](https://github.com/purpleidea/mgmt/).
If you feel that a well used option needs documenting here, please patch it!
###Overview of reference
* [Graph definition file](#graph-definition-file): Main graph definition file.
* [Command line](#command-line): Command line parameters.
###Graph definition file
graph.yaml is the compiled graph definition file. The format is currently
undocumented, but by looking through the [examples/](https://github.com/purpleidea/mgmt/tree/master/examples)
you can probably figure out most of it, as it's fairly intuitive.
###Command line
The main interface to the `mgmt` tool is the command line. For the most recent
documentation, please run `mgmt --help`.
####`--file <graph.yaml>`
Point to a graph file to run.
####`--converged-timeout <seconds>`
Exit if the machine has converged for approximately this many seconds.
####`--max-runtime <seconds>`
Exit when the agent has run for approximately this many seconds. This is not
generally recommended, but may be useful for users who know what they're doing.
####`--noop`
Globally force all resources into no-op mode. This also disables the export to
etcd functionality, but does not disable resource collection, however all
resources that are collected will have their individual noop settings set.
####`--remote <graph.yaml>`
Point to a graph file to run on the remote host specified within. This parameter
can be used multiple times if you'd like to remotely run on multiple hosts in
parallel.
####`--allow-interactive`
Allow interactive prompting for SSH passwords if there is no authentication
method that works.
####`--ssh-priv-id-rsa`
Specify the path for finding SSH keys. This defaults to `~/.ssh/id_rsa`. To
never use this method of authentication, set this to the empty string.
####`--cconns`
The maximum number of concurrent remote ssh connections to run. This defaults
to `0`, which means unlimited.
####`--no-caching`
Don't allow remote caching of the remote execution binary. This will require
the binary to be copied over for every remote execution, but it limits the
likelihood that there is leftover information from the configuration process.
####`--prefix <path>`
Specify a path to a custom working directory prefix. This directory will get
created if it does not exist. This usually defaults to `/var/lib/mgmt/`. This
can't be combined with the `--tmp-prefix` option. It can be combined with the
`--allow-tmp-prefix` option.
####`--tmp-prefix`
If this option is specified, a temporary prefix will be used instead of the
default prefix. This can't be combined with the `--prefix` option.
####`--allow-tmp-prefix`
If this option is specified, we will attempt to fall back to a temporary prefix
if the primary prefix couldn't be created. This is useful for avoiding failures
in environments where the primary prefix may or may not be available, but you'd
like to try. The canonical example is when running `mgmt` with `--remote` there
might be a cached copy of the binary in the primary prefix, but in case there's
no binary available continue working in a temporary directory to avoid failure.
##Examples
For example configurations, please consult the [examples/](https://github.com/purpleidea/mgmt/tree/master/examples) directory in the git
source repository. It is available from:
[https://github.com/purpleidea/mgmt/tree/master/examples](https://github.com/purpleidea/mgmt/tree/master/examples)
### Systemd:
See [`misc/mgmt.service`](misc/mgmt.service) for a sample systemd unit file.
This unit file is part of the RPM.
To specify your custom options for `mgmt` on a systemd distro:
```bash
sudo mkdir -p /etc/systemd/system/mgmt.service.d/
cat > /etc/systemd/system/mgmt.service.d/env.conf <<EOF
# Environment variables:
MGMT_SEEDS=http://127.0.0.1:2379
MGMT_CONVERGED_TIMEOUT=-1
MGMT_MAX_RUNTIME=0
# Other CLI options if necessary.
#OPTS="--max-runtime=0"
EOF
sudo systemctl daemon-reload
```
##Development
This is a project that I started in my free time in 2013. Development is driven
by all of our collective patches! Dive right in, and start hacking!
Please contact me if you'd like to invite me to speak about this at your event.
You can follow along [on my technical blog](https://ttboj.wordpress.com/).
To report any bugs, please file a ticket at: [https://github.com/purpleidea/mgmt/issues](https://github.com/purpleidea/mgmt/issues).
##Authors
Copyright (C) 2013-2016+ James Shubin and the project contributors
Please see the
[AUTHORS](https://github.com/purpleidea/mgmt/tree/master/AUTHORS) file
for more information.
* [github](https://github.com/purpleidea/)
* [&#64;purpleidea](https://twitter.com/#!/purpleidea)
* [https://ttboj.wordpress.com/](https://ttboj.wordpress.com/)
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