3 Simple and fast configuration management (safcm) is written in Go and licensed
6 - *simple*: to use and implement, obvious concepts and less bugs
7 - *fast*: to learn and to use, quickly apply new configurations to your hosts
8 - *configuration management*: sync files, packages, services and run commands
11 The goal is that even unexperienced users (with safcm or configuration
12 management in general) should be able to apply configuration with safcm
13 quickly. This means all key concepts of safcm must be easy to grasp and for
14 each task there should be one obvious way.
16 It can also be read as "saf(e) configuration management" as it combines
17 simplicity and safety in the following principles:
19 - *fail fast*: catch (user) errors as soon as possible; host configuration
20 (including templates) evaluated locally to prevent partial configuration;
21 errors immediately abort the synchronization
22 - *remote hosts untrusted*: clear security boundary between local and remote
23 host; data used from remote hosts is marked (detected groups); all output
24 from remote hosts is escaped to prevent terminal injection attacks; each
25 host only receives its configuration and no data from other hosts
26 - *safety and security*: create files with "write to temporary file", "sync",
27 "rename", "sync directory" for atomicity and durability; guard against
28 symlink and other TOCTOU attacks; extensive test suite
33 This section describes the general concepts, behavior and terminology of
36 Safcm _synchronizes_ _files_, _packages_, _services_ and _commands_ to remote
37 _hosts_. All hosts are explicitly configured. Hosts can be put into _groups_
38 to apply the same configuration to multiple hosts. The host itself is also
39 considered a group for host-specific configuration. In addition to manual
40 group assignment _detected groups_ assign hosts to groups depending on the
41 output of custom commands on the remote host. The configuration for a group
42 contains the files, packages, services and commands which should be applied to
43 all hosts which are members of this group.
45 The configuration of all managed hosts is stored in a directory on the local
46 host. Safcm uses https://yaml.org/[YAML] for all configuration files. However,
47 tasks like copying a file require no explicit configuration (see the
48 documentation for details).
50 Files consist of a tree of files (regular files and symbolic links) and
51 directories with permissions, user/group and content. Files can use
52 _templates_ for dynamic content depending on the host or its groups. Each path
53 can have _trigger_ commands which are executed when the path itself or any
54 sub-paths are modified during synchronization. Packages are package names of
55 the remote operating system. Services are service names of the remote
56 operating system. Commands are shell commands passed to `/bin/sh`.
58 When files with the same path are present in multiple groups of a host an
59 explicit _group order_ must be configured to resolve the conflict. Conflicts
60 do not apply to packages and services which are simply merged from all groups.
61 Commands are appended so that the same command can be executed multiple times.
63 To sync the configuration to a remote host the local `safcm` binary connects
64 to it via `ssh`. It then copies a _remote helper_ binary to `/tmp` on the
65 remote host to later perform the actual sync. If the remote helper is already
66 present, has the proper checksum, permissions and user then the copy is
67 skipped. `safcm` then queries the remote host for information, including
68 operating system, architecture and detected groups. With all relevant data
69 collected it assigns the host its groups, evaluates the configuration
70 including templates and finally sends it to the remote helper which then
71 applies it to the remote host.
73 The synchronization happens in the following order which cannot be changed:
75 . Collect information from remote helper including detected groups
76 . Build configuration for the host and send it to the remote helper
77 . Apply the configuration using the remote helper
80 .. Enable/Start services
84 After the synchronization is complete (or on the first error) the applied
85 changes are displayed. Multiple hosts are synchronized in parallel.
88 == Limitations & Gotchas
90 Besides some obvious limitations due to the simplicity of safcm there are a
91 few issues the user should be aware of. Some of these might get fixed in the
92 future, others are due to the design of safcm.
94 - Commands are executed with `/bin/sh -c` on the remote host which might leak
95 sensitive information to other users via the command line (unless `/proc` is
96 mounted with `hidepid=`). Store sensitive data in a file and execute or
97 source it as a workaround.
99 - Permissions of existing files and directories will be overwritten with the
100 default (root/root, 0644 for files, 0755 for directories) unless manually
101 configured via `permissions.yaml`. This includes important paths like
102 `/root` which often have strict permissions by default, so carefully check
103 the diff output for unwanted changes.
105 - Full file content of all files is sent to the remote during synchronization.
106 This makes it impractical to synchronize large files with safcm. As most
107 configuration files are small this shouldn't be an issue for common
110 - Quoted strings in the output are quoted using Go's `%q` format string. The
111 result is similar -- but not identical -- to quoted strings in regular shell
112 scripts which can be confusing.
117 - build the `safcm` binary and remote helper:
122 * Go support for architecture and operating system, see the "$GOOS and
123 $GOARCH" section in the official
124 https://golang.org/doc/install/source#environment[Go installation guide]
127 * Go support for architecture and operating system
128 * GNU/Linux with common commands (`stat`, `sha512sum`, `cat`, `rm`, `ln`,
131 * to install packages:
132 ** `apt-get` (Debian or derivative)
136 Adding support for other operating systems (e.g. BSDs) or distributions
137 including package managers (e.g. Arch, Gentoo) is easy. Please send patches.
142 Written by Simon Ruderich <simon@ruderich.org>.
147 This program is licensed under GPL version 3 or later.
149 Copyright (C) 2021 Simon Ruderich
151 This program is free software: you can redistribute it and/or modify
152 it under the terms of the GNU General Public License as published by
153 the Free Software Foundation, either version 3 of the License, or
154 (at your option) any later version.
156 This program is distributed in the hope that it will be useful,
157 but WITHOUT ANY WARRANTY; without even the implied warranty of
158 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
159 GNU General Public License for more details.
161 You should have received a copy of the GNU General Public License
162 along with this program. If not, see <http://www.gnu.org/licenses/>.