Environment Variables

The environment acts as an override layer on top of mc.kdl. Secrets are deliberately kept out of the manifest so it can be committed and shared safely: mc reads them from the environment, or from files it generates readable only by the owning user (see Instance Layout).

MC_RCON_PASSWORD

The password for RCON, the remote console protocol used to coordinate backups with a running instance. The environment is the only place it is read from: a "rcon.password" entry in the properties block of the server section is rejected, so the secret never lands in the manifest.

RCON is enabled exactly when a password is configured. When backups are enabled and no password is set anywhere, mc generates one at each start so backups work out of the box; set this variable when other tooling needs to reach the remote console with a known password.

MC_BACKUPS_S3_BUCKET

The S3 bucket that receives backup archives when the backups section names an s3 target. It takes precedence over the bucket written in the manifest.

S3 credentials are not read through mc-specific variables; they come from the standard AWS credential chain — AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY, the ~/.aws configuration files, or an attached IAM role.

MC_DISCORD_WEBHOOK

The Discord webhook URL that notifications are posted to. Setting it is what turns notifications on; without it none are sent. The notifications section of the manifest selects which events are reported — instance lifecycle, crashes, forced shutdowns, and backup results are all on by default.