apply
Lightweight provisioning tool to apply shell scripts on a local or remote machine.
Usage
push
pushes bash scripts called unit
s through ssh to execute:
./push -v units/update units/sshd units/ssh_authorized_keys root@1.2.3.4
Units are processed on the target machine by the run
script. Each unit
executes within its own subshell so no variable leak occurs. Each subshell is
run with set -euo pipefail
. Each subshell also sources the contents of lib
which defines a few convenience functions.
By writing those unit scripts to be idempotent you can just run them again and
again. Units can be aggregated in group
s, which can themselves reference
other groups:
./push -v groups/base groups/ruby units/dockerd root@foo.example.com
You can also define host
s, which are like groups, only they save you some
typing to apply units to multiple targets:
./apply -v hosts/foo.example.com hosts/bar.example.com
The above can be made to process hosts in parallel:
./apply -v -p hosts/foo.example.com hosts/bar.example.com
Since units/
, groups/
, and hosts/
, are just directories and files,
autocompletion works immediately and you could get creative with shell
expansion for arguments.
./apply hosts/{foo,bar}.example.com hosts/test.*
Facts
Sometimes, you may want to provide some configuration for units - e.g. a
hostname, or something similar. If a facts file exists under facts/TARGETNAME
- e.g. facts/foo.example.com
- then it will be uploaded and sourced in every
unit's subshell after lib
. This allows everything from basic variable
exporting to dynamically gathering information about the system's attached
hardware.
Rationale
At some point in a previous company we had a lot of individual VPSes set up basically the same way. I was sick of internal documentation that listed step-by-step commands intertwined with descriptions and manual actions, and any attempt at puppet or ansible just blew up because it was something else to learn by the team (believe me, I tried, it just wouldn't stick with anyone).
So I created apply
.
It turned out to be a deceptively simple, down-to-earth experience, immediately accessible, trivially enabled literate coding, and overall extremely useful both to pragmatically set up and maintain those VPSes as well as creating dev environments, or local VMs to test a e.g one-shot unit performing a change or migration.