Journaldformat

Journaldformat is a term occasionally used to describe the textual representations of entries managed by systemd's journald. Journald collects logs from the kernel, system services, and other sources and stores them in a binary journal. This binary format is optimized for storage efficiency and fast queries and is not intended to be read directly by humans.

For viewing and exporting logs, journalctl provides access to the binary journal in various textual formats. The idea of journaldformat in practice centers on these output options, which control how a record is serialized for human consumption or machine parsing.

Common formats exposed by journalctl -o include:

- short: a compact, single-line-per-entry representation (default)

- short-iso: timestamp in ISO 8601 format

- short-precise: includes higher-precision timestamps

- cat: prints only the MESSAGE field or a straightforward label-to-message view

- json: each entry serialized as a JSON object

- json-pretty: pretty-printed JSON for easier reading

- export: a machine-readable, line-oriented export suitable for pipelines

There is no official separate standard named journaldformat in the core documentation. The term typically refers to the set of textual representations provided by journalctl via the -o option, rather than a standalone file format. Users seeking deterministic, machine-readable logs usually rely on the json or json-pretty formats, while human-readable inspection commonly uses short or short-iso.

See also: journald, journalctl, systemd.