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Configuration
Scheduling

Scheduling

Schedule

Defines when and how often Watchtower checks for new images using a 6-field Cron expression.

Example: --schedule "0 0 4 * * *" runs daily at 4 AM.

            Argument: --schedule, -s
Environment Variable: WATCHTOWER_SCHEDULE
                Type: String
             Default: None
  • Cannot be used with the interval configuration option.
  • Requires a time zone set via TZ or a mounted /etc/localtime file. See Time Zone.

Interval

Sets the interval (in seconds) for polling new images.

            Argument: --interval, -i
Environment Variable: WATCHTOWER_POLL_INTERVAL
                Type: Integer
             Default: 86400 (24 hours)
Cannot be used with --schedule. Overrides cron-based scheduling.

Run Once

Triggers a single update attempt for specified containers and exits immediately.

            Argument: --run-once, -R
Environment Variable: WATCHTOWER_RUN_ONCE
                Type: Boolean
             Default: false
Watchtower automatically sets its own restart policy to “no” in run-once mode to prevent unwanted restarts.

Time Zone

Sets the time zone for Watchtower’s logs and the --schedule flag’s cron expressions.

            Argument: None
Environment Variable: TZ
                Type: String
             Default: UTC
  • To specify a time zone, use a value from the TZ Database (e.g., Europe/Rome).
  • Alternatively, mount the host’s /etc/localtime file using -v /etc/localtime:/etc/localtime:ro.

Update on Start

Performs an update check on startup. If a schedule is configured (via –schedule or –interval), then Watchtower continues with periodic updates.

            Argument: --update-on-start
Environment Variable: WATCHTOWER_UPDATE_ON_START
                Type: Boolean
             Default: false
If used with run-once, a warning is logged and run-once takes precedence.

HTTP API Periodic Polls

Enables periodic updates when the HTTP API update endpoint is active.

            Argument: --http-api-periodic-polls
Environment Variable: WATCHTOWER_HTTP_API_PERIODIC_POLLS
                Type: Boolean
             Default: false
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