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Joachim Wiberg
d9a0c2dce9
The PTY approach caused isatty() to return true for services using the log directive, triggering programs like fprintd (using glib) to emit ANSI escape codes and other TTY-specific formatting in syslog. Using a standard pipe ensures isatty() correctly returns false, so programs produce plain text output suitable for logging. For services that require line-buffered output, users can wrap the command with `stdbuf -oL` as documented in doc/config/logging.md. Fixes #455 Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
64 lines
2.1 KiB
Markdown
64 lines
2.1 KiB
Markdown
General Logging
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===============
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**Syntax:** `log size:200k count:5`
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Log rotation for run/task/services using the `log` sub-option with
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redirection to a log file. Global setting, applies to all services.
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The size can be given as bytes, without a specifier, or in `k`, `M`,
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or `G`, e.g. `size:10M`, or `size:3G`. A value of `size:0` disables
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log rotation. The default is `200k`.
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The count value is recommended to be between 1-5, with a default 5.
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Setting count to 0 means the logfile will be truncated when the MAX
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size limit is reached.
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Redirecting Output
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------------------
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The `run`, `task`, and `service` stanzas also allow the keyword `log` to
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redirect `stderr` and `stdout` of the application to a file or syslog
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using the native `logit` tool. This is useful for programs that do not
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support syslog on their own, which is sometimes the case when running
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in the foreground.
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The full syntax is:
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log:/path/to/file
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log:prio:facility.level,tag:ident
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log:console
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log:null
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log
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Default `prio` is `daemon.info` and default `tag` is the basename of the
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service or run/task command.
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Log rotation is controlled using the global `log` setting.
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**Example:**
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service log:prio:user.warn,tag:ntpd /sbin/ntpd pool.ntp.org -- NTP daemon
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Output Buffering
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----------------
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When using the `log` directive, Finit redirects the service's stdout and
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stderr to a pipe connected to a logger process. Programs detect this as
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non-interactive output (i.e., `isatty()` returns false) and typically
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switch from line-buffered to fully-buffered mode.
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Most well-behaved daemons explicitly flush their output or use syslog
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directly, so this is rarely an issue. However, if a service's log
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messages appear delayed or batched, you can force line-buffered output
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by wrapping the command with `stdbuf`:
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service log /usr/bin/stdbuf -oL /path/to/command -- My service
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The `-oL` option forces line-buffered output, and `-o0` forces unbuffered
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output. See `stdbuf(1)` for details.
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> [!NOTE]
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> Using `stdbuf` is rarely necessary. Only use it if you observe actual
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> buffering issues with a specific service.
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