Title : Configuration deployment made easy with drist
Author: Solène
Date  : 29 November 2018
Tags  : unix drist automation

Hello, in this article I will present you my deployement tool **drist** (if you
speak Russian, I am already aware of what you think). It reached a feature
complete status today and now I can write about it.

As a system administrator, I started using *salt* a few years ago. And
honestly, I can not cope with it anymore. It is slow, it can get very
complicated for some tasks like correctly ordering commands and a
configuration file can become a nightmare when you start using condition in it.

You may already have read and heard a bit about **drist** as I wrote an article
about my presentation of it at bitreichcon 2018.


### History

I also tried alternatives like *ansible*, *puppet*, *Rex* etc... One day, when
lurking in the ports tree, I found **sysutils/radmind** which got a lot
interest from me even if it is really poorly documented. It is a project from
1995 if I remember correctly, but I liked the base idea. *Radmind* works with
files, you create a known working set of files for your system, and you can
propagate that whole set to other machines, or see differences between the
reference and the current system. Sets could be negative, meaning that the
listed files should not be present on the system, but it was also possible to
add extra sets for specific hosts. The whole thing is really really cumbersome,
this requires a lot of work, I found little documentation etc... so I did not
used it but, that lead me to write my own deployment tool using ideas from
*radmind* (working with files) and from *Rex* (using a script for doing
changes).


### Concept

**drist** aims at being simple to understand and pluggable with standard tools.
There is no special syntax to learn, no daemon to run, no agent, and it relies
on base tools like awk, sed, ssh and rsync.

**drist** is cross platform as it has a few requirements but it is not well
suited for deploying on too much differents operating systems.

When executed, **drist** will execute six steps in a specific order, you can
use only steps you need.

Shamelessly copied from the man page, explanations after:

1. If folder **files** exists, its content is copied to server rsync(1).
2. If folder **files-HOSTNAME** exists, its content is copied to server using rsync(1).
3. If folder **absent** exists, filenames in it are deleted on server.
4. If folder **absent-HOSTNAME** exists, filenames in it are deleted on server.
5. If file **script** exists, it is copied to server and executed there.
6. If file **script-HOSTNAME** exists, it is copied to server and executed there.

In the previous list, all the existences checks are done from the current
working directory where drist is started. The text **HOSTNAME** is replaced by
the output of `uname -n` of the remote server, and files are copied starting from
the root directory.

drist does not do anything more. In a more litteral manner, it copies files to
the remote server, using a local filesystem tree (folder **files**). It will
delete on the remote server all files present in the local filesystem tree
(folder **absent**), and it will run on the remote server a script named
**script**.

Each of theses can be customized per-host by adding a "-HOSTNAME" suffix to the
folder or file name, because experience taught me that some hosts does require
specific configuration.

If a folder or a file does not exist, **drist** will skip it. So it is possible
to only copy files, or only execute a script, or delete files and execute a
script after.


### Drist usage

The usage is pretty simple. **drist** has 3 flags which are optionals.

- -n flag will show what happens (simuation mode)
- -s flag tells drist to use sudo on the remote host
- -e flag with a parameter will tell drist to use a specific path for the sudo
  program

The remote server address (ssh format like user@host) is mandatory.

    $ drist my_user@my_remote_host

drist will look at files and folders in the current directory when executed,
this allow to organize as you want using your filesystem and a revision control
system.


### Simple examples

Here are two examples to illustrate its usage. The examples are easy, for
learning purpose.


#### Deploying ssh keys

I want to easily copy my users ssh keys to a remote server.

    $ mkdir drist_deploy_ssh_keys
    $ cd drist_deploy_ssh_keys
    $ mkdir -p files/home/my_user1/.ssh
    $ mkdir -p files/home/my_user2/.ssh
    $ cp -fr /path/to/key1/id_rsa files/home/my_user1/.ssh/
    $ cp -fr /path/to/key2/id_rsa files/home/my_user2/.ssh/
    $ drist user@remote-host
    Copying files from folder "files":
    	/home/my_user1/.ssh/id_rsa
    	/home/my_user2/.ssh/id_rsa


#### Deploying authorized_keys file

We can easily create the authorized_key file by using cat.

    $ mkdir drist_deploy_ssh_authorized
    $ cd drist_deploy_ssh_authorized
    $ mkdir -p files/home/user/.ssh/
    $ cat /path/to/user/keys/*.pub > files/home/user/.ssh/authorized_keys
    $ drist user@remote-host
    Copying files from folder "files":
    	/home/user/.ssh/authorized_keys

This can be automated using a makefile running the cat command and then running
drist.

    all:
    	cat /path/to/keys/*.pub > files/home/user.ssh/authorized_keys
	drist user@remote-host


#### Installing nginx on FreeBSD

This module (aka a folder which contain material for drist) will install nginx
on FreeBSD and start it.

    $ mkdir deploy_nginx
    $ cd deploy_nginx
    $ cat >script <<EOF
    #!/bin/sh
    test -f /usr/local/bin/nginx
    if [ $? -ne 0 ]; then
    	pkg install -y nginx
    fi
    sysrc nginx_enable=yes
    service nginx restart
    EOF
    $ drist user@remote-host
    Executing file "script":
    	Updating FreeBSD repository catalogue...
    	FreeBSD repository is up to date.
    	All repositories are up to date.
    	The following 1 package(s) will be affected (of 0 checked):
    	
    	New packages to be INSTALLED:
    	        nginx: 1.14.1,2
    	
    	Number of packages to be installed: 1
    	
    	The process will require 1 MiB more space.
    	421 KiB to be downloaded.
    	[1/1] Fetching nginx-1.14.1,2.txz: 100%  421 KiB 430.7kB/s    00:01
    	Checking integrity... done (0 conflicting)
    	[1/1] Installing nginx-1.14.1,2...
    	===> Creating groups.
    	Using existing group 'www'.
    	===> Creating users
    	Using existing user 'www'.
    	[1/1] Extracting nginx-1.14.1,2: 100%
    	Message from nginx-1.14.1,2:
    	
    	===================================================================
    	Recent version of the NGINX introduces dynamic modules support.  In
    	FreeBSD ports tree this feature was enabled by default with the DSO
    	knob.  Several vendor's and third-party modules have been converted
    	to dynamic modules.  Unset the DSO knob builds an NGINX without
    	dynamic modules support.
    	
    	To load a module at runtime, include the new `load_module'
    	directive in the main context, specifying the path to the shared
    	object file for the module, enclosed in quotation marks.  When you
    	reload the configuration or restart NGINX, the module is loaded in.
    	It is possible to specify a path relative to the source directory,
    	or a full path, please see
    	https://www.nginx.com/blog/dynamic-modules-nginx-1-9-11/ and
    	http://nginx.org/en/docs/ngx_core_module.html#load_module for
    	details.
    	
    	Default path for the NGINX dynamic modules is
    	
    	/usr/local/libexec/nginx.
    	===================================================================
    	nginx_enable:  -> yes
    	Performing sanity check on nginx configuration:
    	nginx: the configuration file /usr/local/etc/nginx/nginx.conf syntax is ok
    	nginx: configuration file /usr/local/etc/nginx/nginx.conf test is successful
    	nginx not running? (check /var/run/nginx.pid).
    	Performing sanity check on nginx configuration:
    	nginx: the configuration file /usr/local/etc/nginx/nginx.conf syntax is ok
    	nginx: configuration file /usr/local/etc/nginx/nginx.conf test is successful
    	Starting nginx.


### More complex example

Now I will show more complexes examples, with host specific steps. I will not
display the output because the previous output were sufficient enough to give a
rough idea of what drist does.


#### Removing someone ssh access

We will reuse an existing module here, an user should not be able to login
anymore on its account on the servers using the ssh key.

    $ cd ssh
    $ mkdir -p absent/home/user/.ssh/
    $ touch absent/home/user/.ssh/authorized_keys
    $ drist user@server


#### Installing php on FreeBSD

The following module will install php and remove the opcache.ini file, and will
install php72-pdo_pgsql if it is run on server *production.domain.private*.

    $ mkdir deploy_php && cd deploy_php
    $ mkdir -p files/usr/local/etc
    $ cp /some/correct/config.ini files/usr/local/etc/php.ini
    $ cat > script <<EOF
    #!/bin/sh
    test -f /usr/local/etc/php-fpm.conf || pkg install -f php-extensions
    sysrc php_fpm_enable=yes
    service php-fpm restart
    test -f /usr/local/etc/php/opcache.ini || rm /usr/local/etc/php/opcache.ini
    EOF
    $ cat > script-production.domain.private <<EOF
    #!/bin/sh
    test -f /usr/local/etc/php/pdo_pgsql.ini || pkg install -f php72-pdo_pgsql
    service php-fpm restart
    EOF


#### The monitoring machine

This one is unique and I would like to avoid applying its configuration against
another server (that happened to me once with salt and it was really really
bad). So I will just do all the job using the hostname specific cases.

    $ mkdir my_unique_machine && cd my_unique_machine
    $ mkdir -p files-unique-machine.private/usr/local/etc/{smokeping,munin}
    $ cp /good/config files-unique-machine.private/usr/local/etc/smokeping/config
    $ cp /correct/conf files-unique-machine.private/usr/local/etc/munin/munin.conf
    $ cat > script-unique-machine.private <<EOF
    #!/bin/sh
    pkg install -y smokeping munin-master munin-node
    munin-configure --shell --suggest | sh
    sysrc munin_node_enable=yes
    sysrc smokeping_enable=yes
    service munin-node restart
    service smokeping restart
    EOF
    $ drist user@incorrect-host
    $ drist user@unique-machine.private
    Copying files from folder "files-unique-machine.private":
    	/usr/local/etc/smokeping/config
    	/usr/local/etc/munin/munin.conf
    Executing file "script-unique-machine.private":
        [...]

Nothing happened on the wrong system.


#### Be creative

Everything can be automated easily. I have some makefile in a lot of my drist
modules, because I just need to type "make" to run it correctly. Sometimes it
requires concatenating files before being run, sometimes I do not want to make
mistake or having to remember on which module apply on which server (if it's
specific), so the makefile does the job for me.

One of my drist module will look at all my SSL certificates from another
module, and make a reed-alert configuration file using awk and deploying it on
the monitoring server. All I do is typing "make" and enjoy my free time.


### How to get it and install it

- Drist can be downloaded [at this address](ftp://ftp.bitreich.org/releases/drist/drist-v1.02.tgz).
- Sources can be cloned using `git clone git://bitreich.org/drist`

In the sources folder, type "make install" as root, that will copy drist binary
to /usr/bin/drist and its man page to /usr/share/man/man1/drist.1

For copying files, drist requires rsync on both local and remote hosts.

For running the script file, a sh compatible shell is required (csh is not working).