= README Simple and fast configuration management (safcm) is written in Go and licensed under GPLv3+. It is: - *simple*: to use and implement, obvious concepts and less bugs - *fast*: to learn and to use, quickly apply new configurations to your hosts - *configuration management*: sync files, packages, services and run commands on remote hosts The goal is that even inexperienced users (with safcm or configuration management in general) should be able to apply configuration with safcm quickly. This means all key concepts of safcm must be easy to grasp and for each task there should be one obvious way. It can also be read as "saf(e) configuration management" as it combines simplicity and safety in the following principles: - *fail fast*: catch (user) errors as soon as possible; host configuration (including templates) is evaluated locally to prevent partial configuration; errors immediately abort the synchronization - *remote hosts are untrusted*: clear security boundary between local and remote host; data used from remote hosts is marked tainted (detected groups); all output from remote hosts is escaped to prevent terminal injection attacks; each host only receives its own configuration and no data from other hosts - *safety and security*: create files with "write to temporary file", "sync", "rename", "sync directory" for atomicity and durability; implemented in a memory safe language and using a simple synchronization protocol to prevent attacks on the local host; guard against symlink and other TOCTOU attacks; extensive test suite == Overview This section describes the general concepts, behavior and terminology of safcm. Safcm _synchronizes_ _files_, _packages_, _services_ and _commands_ to remote _hosts_. All hosts are explicitly configured. Hosts can be put into _groups_ to apply the same configuration to multiple hosts. The host itself is also considered a group for host-specific configuration. In addition to manual group assignment _detected groups_ assign hosts to groups depending on the output of custom commands on the remote host. The configuration for a group contains the files, packages, services and commands which should be applied to all hosts which are members of this group. The configuration of all managed hosts is stored in a directory on the local host. Safcm uses https://yaml.org/[YAML] for all configuration files. Strict type checks prevent potential pitfalls due to the complex YAML syntax. Tasks like copying a file require no explicit configuration. Files (regular files and symbolic links) and directories, including permissions, user/group and content are kept in a regular filesystem tree on the local host. Files can use _templates_ for dynamic content depending on the host or its groups. Each path can have _trigger_ commands which are executed when the path itself or any sub-paths are modified during synchronization. Packages are package names of the remote operating system. Services are service names of the remote operating system. Commands are shell commands passed to `/bin/sh`. When files with the same path are present in multiple groups of a host, an explicit _group priority_ must be configured to resolve the conflict. Conflicts do not apply to packages and services which are simply merged from all groups. Commands are appended so that the same command can be executed multiple times. To sync the configuration to a remote host, the local `safcm` binary connects to it via `ssh`. It then copies a _remote helper_ binary to `/tmp` on the remote host to perform the actual sync later. If the remote helper is already present, has the proper checksum, permissions and user/group then the copying step is skipped. `safcm` then queries the remote host for information, including operating system, architecture and detected groups. With all relevant data collected, it assigns the host to its groups, evaluates the configuration including templates and finally sends the new configuration to the remote helper which then applies it to the remote host. The synchronization happens in the following order which cannot be changed: . Collect information from remote helper including detected groups . Build configuration for the host and send it to the remote helper . Apply the configuration using the remote helper .. Synchronize files .. Install packages .. Enable/Start services .. Run triggers .. Run commands After the synchronization is complete (or on the first error) the applied changes are displayed. Multiple hosts are synchronized in parallel. == Limitations & Gotchas Besides some obvious limitations due to the simplicity of safcm there are a few issues the user should be aware of. Some of these might get fixed in the future, others are due to the design of safcm. - Commands are executed with `/bin/sh -c` on the remote host which might leak sensitive information to other users via the command line (unless `/proc` is mounted with `hidepid=` on GNU/Linux systems). Store sensitive data in a file and execute or source it as a workaround. - Permissions of existing files and directories will be overwritten with the default (root/root or root/wheel, 0644 for files, 0755 for directories) unless manually configured via `permissions.yaml`. This includes important paths like `/root` which often have strict permissions by default, so carefully check the output for unwanted changes. - The full file content of all files is sent to the remote during synchronization. This makes it impractical to synchronize large files with safcm. Since most configuration files are small this shouldn't be an issue for common scenarios. - Quoted strings in the output are quoted using Go's `%q` format string. The result is similar -- but not identical -- to quoted strings in regular shell scripts which can be confusing. - Permissions of symlinks are ignored on BSD systems. They are always shown to have `0777` as permissions even though the current umask controls the actual permissions when creating new symlinks. Existing symlinks with different permissions are not updated. Most BSDs ignore the permissions when following symlinks which should reduce the impact of this limitation. == Requirements - to build the `safcm` binary and remote helper: * Go >= 1.16 (for `go:embed`, `io/fs`) * GNU make - local host: * Go support for architecture and operating system, see the "$GOOS and $GOARCH" section in the official https://golang.org/doc/install/source#environment[Go installation guide] - *remote hosts*: * Go support for architecture and operating system * Supported operating system: ** GNU/Linux with common commands (`uname`, `id`, `stat`, `sha512sum`, `cat`, `mktemp`, `rm`, `ln`, `chmod`) ** FreeBSD (same commands, but uses `sha512`) ** OpenBSD (same commands, but uses `sha512`) * SSH server * to install packages: ** `apt-get` (Debian or derivative) * to sync services: ** `systemd` Adding support for other operating systems (e.g. BSDs) or distributions including package managers (e.g. Arch, Gentoo) is easy. Please send patches. At the moment the remote helper is built for the following operating systems ($GOOS) and architectures ($GOARCH). To add more architectures simply edit `cmd/safcm-remote/build.sh`. - freebsd: amd64 - linux: amd64, armv7 - openbsd: amd64 == Authors Written by Simon Ruderich . == License This program is licensed under GPL version 3 or later. Copyright (C) 2021 Simon Ruderich This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see .