System files

AIStore stores, maintains, and utilizes a number of system files that serve a variety of different purposes.

For the most recently updated system filenames and configuration directories, please see fname/fname.go source.

This section tries to enumerate the system files and briefly describe their respective usages.

First, there’s a node configuration usually derived from a single configuration template and populated at deployment time.

Local Playground: a single configuration template and the script we use to populate it when we run the cluster locally on our development machines;
Production K8s deployment: a set of ansible playbooks to automate creation of a node’s configuration files via a custom K8s operator and to deploy multiple nodes across a K8s cluster.

The second category of system files and directories includes:

Name	Type	Node	Brief Description	Description
`.ais.bmd`	file	gateway	Buckets Metadata	Names and properties of all buckets, including replicated remote buckets and remote AIStore buckets
`.ais.smap`	file	gateway and target	Cluster Map	Description of whole cluster which includes IDs and IPs of all the nodes.
`.ais.rmd`	file	storage target	Rebalancing State	Used internally to make sure that cluster-wide rebalancing runs to completion in presence of all possible events including cluster membership changes and cluster restarts.
`.ais.markers/`	dir	storage target	Persistent state markers	Used for many purposes like determining node restart or rebalance/resilver abort. The role of the markers is to survive potential node’s process crash (eg. due to power outage or mistake).
`.ais.proxy_id`	file	gateway	Gateway node id	Used during node startup to detect a node ID if not specified with `-daemon_id`. Note: storage targets also try to detect a node ID, but by looking for the extended attribute `user.ais.daemon_id` on its filesystem.

Thirdly, there are also AIS components and tools, such as AIS authentication server and AIS CLI. Authentication server, if enabled, creates a sub-directory .authn that contains:

Name	Description
`authn.json`	AuthN server configuration
`authn.db`	Registered clusters, a token blacklist, user roles, user credentials and permissions

And on the machine where you run AIS CLI expect to see the following two files (by default, under ~/.config/ais/cli/):

Name	Description
`cli.json`	Configuration file (if doesn’t exist, the config gets created and populated with default values upon the first CLI run)
`auth.token`	The token file is created iff `AuthN` (see above) is running and CLI user logged-in (via `ais auth login` command). The `auth.token` is then used to make the requests to the cluster and manage users and their permissions. When a logged-in user signs out, the token file gets removed.

Finally, there’s also ais.db that each AIS node may store locally to maintain component-specific runtime information in the form of key-value records. The components in-question include dSort and Downloader and the example of the stored information would be running downloading jobs and their errors (if any).