CLI reference

Commands

ocync sync -c config.yaml               Sync images from config
ocync sync -c config.yaml --dry-run     Preview what would sync
ocync sync -c config.yaml --json        Output sync report as JSON
ocync copy <source> <destination>       Copy a single image
ocync tags <repository>                 List and filter tags
ocync watch -c config.yaml              Continuous sync on a schedule
ocync analyze -c config.yaml            Analyze blob sharing potential
ocync auth check -c config.yaml         Verify registry credentials
ocync validate config.yaml              Validate config without connecting
ocync expand config.yaml                Show config with env vars resolved
ocync version                           Print version and build info

Global options

sync

Sync images defined in a config file:

ocync sync -c config.yaml
ocync sync -c config.yaml --dry-run
ocync sync -c config.yaml --json

Dry-run output

--dry-run runs the full filter pipeline against each mapping’s source tags and prints, per mapping:

• source tags: N — the number of tags fetched from the source.
• include path: — exact tag names from include: synced without going through the rest of the pipeline. Glob patterns in include: (like *-dev) flow through the regular pipeline and show up in the rows below, not here. Default cap is 5 names; -v removes the cap.
• filter: — per-stage attrition (glob, semver, exclude, sort, keep latest). Each row shows count_in -> count_out and the drop count.
• kept (N): — the final tags. When include: is used, rescued tags are listed first and tagged [via include] so the rescue path is visible.
• dropped (N): — Pareto-sorted drop attribution (largest cause first), with sample tag names per reason. Default cap is 5 names per reason; -v removes the cap.
• min_tags: N — when min_tags: is configured, the line prints kept M, satisfied or kept M, real sync will FAIL with BelowMinTags. Real-sync (no --dry-run) errors out below min_tags; dry-run shows the report and surfaces the gap so the configuration can be fixed before running.

copy

Copy a single image between registries:

ocync copy cgr.dev/chainguard/nginx:latest \
    123456789012.dkr.ecr.us-east-1.amazonaws.com/nginx:latest

The source reference must include a tag. The destination tag defaults to the source tag if omitted.

tags

List and filter tags for a repository:

ocync tags docker.io/library/nginx
ocync tags cgr.dev/chainguard/nginx --semver ">=1.0" --latest 10

watch

Continuous sync on a schedule with health endpoints:

ocync watch -c config.yaml --interval 600 --health-port 8080

See observability for health endpoint details.

analyze

Analyze blob sharing and cross-repo mount potential without performing a sync. Pulls source manifests only (no blobs transferred) and reports total unique blobs, shared blobs across images, deduplicated bytes saved, and per-target mount opportunities.

ocync analyze -c config.yaml
ocync analyze -c config.yaml --json

Use analyze to estimate transfer savings before running a full sync, or to verify that blob deduplication and mounting are configured correctly.

validate

Validate a config file without connecting to registries:

ocync validate config.yaml

Checks config syntax, structure, and references (registry names, target groups) without making any network requests. Catches errors before attempting a sync. Exits with code 0 on success or 3 on invalid configuration.

expand

Show config with all environment variables resolved:

ocync expand config.yaml
ocync expand config.yaml --show-secrets

auth check

Verify registry credentials for all registries in a config:

ocync auth check -c config.yaml
ocync auth check -c config.yaml -c config2.yaml

Exit codes

Structured output

Use --json to get machine-readable sync reports for CI/CD pipelines:

ocync sync -c config.yaml --json

The JSON output includes per-image results, aggregate statistics (blobs transferred, bytes, mounts, cache hits), and any errors encountered.

Environment variables