The document discusses the deployment and configuration management tool 'Rex', which allows for remote execution of batched commands similarly to Ansible. It outlines its features, installation methods, and practical examples of using 'Rex' for tasks like package management and server configuration. The author emphasizes the community-driven aspect of 'Rex' and highlights its flexibility and active development.

1. (R)?ex
Deployment & Configuration
Management
Andy Beverley
andy@andybev.com

2. Contents
● Introduction
– Why this talk
– What is Rex
● General features
● Why I use Rex
● Installation
● General examples
● How I use Rex

3. Why this talk?
● Rex not as well known as other orchestration
tools
● I'm a recent convert - spread the word!

4. What is Rex?
● "Remote Execution"
● Easily run batched commands remotely
● Similar in concept to Ansible (push not pull)
● Start with Rexfile (Makefile)
● A Rexfile contains tasks

5. General features
● Group by server type
● Very flexible scripting (Perl)
– Minimal Perl knowledge required
– Strength and a weakness?
● Many modules, or add your own (to core?)
● Augeas interface
● Transactions and rollback
● Store config in database

6. Why I use Rex
● Community not commercial
● Very helpful maintainers and mailing list
● Fast merges for PRs
● Very active project
● Flexible

7. Installation
● Packages available for most distributions
● Or:
– cpan Rex

8. Example Rexfile
set connection => "OpenSSH";
user "root";
private_key "~/.ssh/id_rsa";
public_key "~/.ssh/id_rsa.pub";
key_auth;
task "say_uptime", sub {
say run "uptime"
};

9. Running a Rexfile
$ rex say_uptime
$ rex -H myhost say_uptime

10. Updating packages
use Rex::Commands::Pkg;
task "upgrade", sub {
update_package_db;
update_system;
};
● Tasks can be contained in your own common modules

11. Installing and configuring
task "setup_ntp", sub {
install "ntp";
};

12. Installing and configuring
task "setup_ntp", sub {
pkg "ntp", ensure => "latest";
service ntp => ensure => "started";
};

13. Installing and configuring
task "setup_ntp", sub {
pkg "ntp", ensure => "latest";
file "/etc/ntp.conf",
source => "files/etc/ntp.conf";
service ntp => ensure => "started";
};

14. Installing and configuring
task "setup_ntp", sub {
pkg "ntp", ensure => "latest";
file "/etc/ntp.conf",
source => "files/etc/ntp.conf",
owner => "root",
group => "root",
mode => 644;
service ntp => ensure => "started";
};

15. Installing and configuring
task "setup_ntp", sub {
pkg "ntp", ensure => "latest";
file "/etc/ntp.conf",
source => "files/etc/ntp.conf",
owner => "root",
group => "root",
mode => 644,
on_change => sub {
service ntp => "restart"
};
service ntp => ensure => "started";
};

16. File command
file "/etc/hosts",
content => template("templates/etc/hosts.tpl"),
owner => "user",
group => "group",
mode => 700,
on_change => sub { say "Something was changed." };

17. File command
file "/etc/named.conf",
content => template("templates/etc/named.conf.tpl"),
no_overwrite => TRUE;

18. File command
file "/etc/motd",
ensure => "absent";
delete_lines_matching
"/var/log/auth.log" => "root";
append_if_no_such_line
"/etc/groups", "mygroup:*:100:myuser1,myuser2";
append_or_amend_line "/etc/groups",
line => "mygroup:*:100:myuser3,myuser4",
regexp => qr{^mygroup};

19. Server groups
group web_servers =>
"web1", "web2", "web3";
group web_servers => "web[1..3]";
group servers =>
"web[1..3]", "db[01..02]", "mail";

20. Server groups
task "uptime", group => "web_servers",
sub { say uptime; };

21. Augeas interface
augeas modify =>
"/files/etc/postfix/main.cf/myhostname"
=> "myhost",
"/files/etc/postfix/main.cf/relayhost"
=> "smtp.isp.com";

22. Augeas interface
augeas modify =>
"/files/etc/postfix/main.cf/myhostname"
=> "myhost",
"/files/etc/postfix/main.cf/relayhost"
=> "smtp.isp.com",
on_change => sub {
service postfix => "restart";
};

23. Transactions
task "do-something", "server01", sub {
on_rollback {
rmdir "/tmp/mydata";
};
transaction {
mkdir "/tmp/mydata";
upload "files/myapp.tar.gz", "/tmp/mydata";
run "cd /tmp/mydata; tar xzf myapp.tar.gz";
if ($? != 0) {
die("Error extracting myapp.tar.gz");
}
};
};

24. How I use Rex
● Central configuration database
● Extract server groups from database
● Set of "base" tasks
● Other tasks depending on server type
$ rex -H newserver web_server

25. How I use Rex
include qw/
Common::SSH
Common::Web
/;
task "base", group => "base", sub {
Common::SSH::clampdown();
};
task "install_gads", group => "gads_servers", sub {
base();
Common::Web::install_app(
base_domain => 'ctrlo.com',
cert_domain => 'gads.ctrlo.com',
);
};

26. Config from database
use JSON;
my $groups = json_decode(
`configdb.pl --type server --action summary`
);
foreach my $group (@$groups) {
my $type = $group->{type};
my @servers = @{$group->{servers}};
group $type => @servers;
}
task "setup_apache", group => "web", sub {
...
};

27. Certs from database
use Rex::Commands::File;
use IPC::Run3;
use JSON;

28. Certs from database
my $certs = decode_json(
`configdb.pl --type cert --server $hostname`
);
foreach my $cert (@$certs) {
if ($cert->{type} eq 'key') {
my $key = $cert->{content};
my $out;
run3 "openssl rsa -passin pass:'$pass'", $key, $out;
file $cert->{filename},
content => $out,
owner => "root",
group => "ssl-cert",
mode => 640,
on_change => sub { ... }; # e.g. restart web server
}
}

29. www.rexify.org
Andy Beverley
andy@andybev.com