Files on disk

mito keeps two small pieces of state outside your project. Neither one holds credentials, and neither names a bucket or an object.

Security and privacy covers the wider picture.

   ~/.local/share/mitosync/cloud_metrics.json   API call counters   (Linux)
   ~/Library/Application Support/MitoSync/      same               (macOS)

   ~/.mitosync/pricing_cache.json               S3 price table     (both)

   ./results.json                               only when you ask with -o

Metrics

The cumulative API counters behind mito stats, stored as cloud_metrics.json:

The directory is created on first use, recursively, because ~/.local/share does not exist on a minimal install.

Deleting the file resets the counters.

mito stats --reset does not delete it. It clears the counters in memory and writes an empty metrics file over the top. If that write fails, the command reports the failure and exits 1 rather than claiming a reset that never happened.

Pricing cache

The S3 price table used for cost estimates, cached as pricing_cache.json in ~/.mitosync/, keyed by region with a 24-hour lifetime.

The prices are built-in per-region defaults compiled into the binary, not fetched from AWS. Live lookup against the AWS Pricing API is not implemented (#106), so the cache currently stores the same table the binary already contains and the file earns nothing. It exists for the day the lookup lands.

Deleting the file is harmless.

Note that the two files live in different directories. The pricing cache uses ~/.mitosync/ on every platform, while metrics follow the platform convention. That is a wrinkle, not a design statement.

AWS credentials

mito reads the standard AWS chain and writes nothing to it:

• AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN
• ~/.aws/credentials and ~/.aws/config, including named profiles
• An ECS task role

Named profiles are selected per S3 side with --source-profile and --dest-profile. See Cross-account S3.

EC2 instance roles do not work.

mito sets AWS_EC2_METADATA_DISABLED=true at startup, unconditionally, overwriting any value you set.

The reason: off an EC2 instance, an instance-metadata lookup can only ever time out, and it adds that timeout to every cold start. Disabling it removes the delay.

The cost: on an actual EC2 instance, it also removes instance-role credentials from the chain. A run that relies on them will fail to authenticate. Use environment variables, a profile, or an ECS task role there.

What gets written where you run it

Report files, and only when you ask for one:

mito diff ./data/ s3://my-bucket/data/ -o results.json

Nothing else is written to the working directory.

There is one exception, as a fallback. If the application data directory cannot be determined and cannot be created, metrics land in the current directory instead.

Scratch state in S3

Comparing a remote object creates a scratch multipart upload, and aborts it on every path out including the error paths. See Architecture.

If a process is killed hard enough to skip that abort, the parts are left behind and S3 keeps billing for them. mito leftovers is how you find and clear those.