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Title: Configuration deployment made easy with drist
Author: Solène
Date: 29 November 2018
Tags: unix drist automation
Description:
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.
### 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):
dataswamp.org:70 /~solene/article-drist-intro:198: port field too long