Systemd
在不重新載入的情況下更改正在執行的 SystemD 服務的 JournalD 日誌級別
我有一個用 Python 編寫的簡單服務，它使用 SystemD JournalHandler 進行日誌記錄（SysLogHandler 應該類似地工作）。
# myservice.py import time import logging from systemd.journal import JournalHandler log = logging.getLogger('demo') log.addHandler(JournalHandler()) log.setLevel(logging.DEBUG) while True: log.debug("debug") log.info("info") log.warning("warning") log.error("error") time.sleep(3)這是執行此服務的 SystemD 配置：
# myservice.service [Unit] Description=Python logging test [Service] ExecStart=/usr/bin/python3 .../myservice.py Type=simple [Install] WantedBy=multi-user.target現在這將始終將所有內容記錄到 JournalD：
# journalctl -f Mar 06 15:58:13 myhost .../myservice.py[12852]: debug Mar 06 15:58:13 myhost .../myservice.py[12852]: info Mar 06 15:58:13 myhost .../myservice.py[12852]: warning Mar 06 15:58:13 myhost .../myservice.py[12852]: error是否可以在執行時更改此 SystemD 服務的日誌記錄配置，在它已經啟動（使用級別 DEBUG）之後 - 無需重新載入/重新啟動服務？我想完全避免在我的 Python 程式碼中設置日誌級別，而是讓 SystemD 處理日誌級別。
基本上我想這樣稱呼：
# Log everything to JournalD change-systemd-service-loglevel myservice DEBUG # Ignore all logs < WARNING, these should not show up on journalctl change-systemd-service-loglevel myservice WARNING
相反，如果選擇寫入日誌的內容，通常記錄所有內容，然後從日誌中過濾您想要的內容。這樣，如果出現問題，您將能夠在不重現問題的情況下閱讀調試內容。
您可以使用
journalctl --priority過濾日誌級別。man journalctl說：-p, --priority= Filter output by message priorities or priority ranges. Takes either a single numeric or textual log level (i.e. between 0/"emerg" and 7/"debug"), or a range of numeric/text log levels in the form FROM..TO. The log levels are the usual syslog log levels as documented in syslog(3), i.e. "emerg" (0), "alert" (1), "crit" (2), "err" (3), "warning" (4), "notice" (5), "info" (6), "debug" (7). If a single log level is specified, all messages with this log level or a lower (hence more important) log level are shown. If a range is specified, all messages within the range are shown, including both the start and the end value of the range. This will add "PRIORITY=" matches for the specified priorities.我執行了你的 python 腳本幾秒鐘來展示。在我的終端
debug中是灰色的、info白色warning的、琥珀色的和error紅色的。案例1：沒有過濾器。
$ journalctl --user -u pylog --no-hostname Mar 07 08:54:03 systemd[1064]: Started Python logging test. Mar 07 08:54:03 /home/stew/bin/pylog.py[953165]: debug Mar 07 08:54:03 /home/stew/bin/pylog.py[953165]: info Mar 07 08:54:03 /home/stew/bin/pylog.py[953165]: warning Mar 07 08:54:03 /home/stew/bin/pylog.py[953165]: error Mar 07 08:54:06 /home/stew/bin/pylog.py[953165]: debug Mar 07 08:54:06 /home/stew/bin/pylog.py[953165]: info Mar 07 08:54:06 /home/stew/bin/pylog.py[953165]: warning Mar 07 08:54:06 /home/stew/bin/pylog.py[953165]: error案例 2：警告過濾器（詳細語法）
$ journalctl --user -u pylog --no-hostname --priority=warning Mar 07 08:54:03 /home/stew/bin/pylog.py[953165]: warning Mar 07 08:54:03 /home/stew/bin/pylog.py[953165]: error Mar 07 08:54:06 /home/stew/bin/pylog.py[953165]: warning Mar 07 08:54:06 /home/stew/bin/pylog.py[953165]: error案例 3：資訊和警告範圍過濾器（簡單語法）
$ journalctl --user -u pylog --no-hostname -p 4..6 Mar 07 08:54:03 systemd[1064]: Started Python logging test. Mar 07 08:54:03 /home/stew/bin/pylog.py[953165]: info Mar 07 08:54:03 /home/stew/bin/pylog.py[953165]: warning Mar 07 08:54:06 /home/stew/bin/pylog.py[953165]: info Mar 07 08:54:06 /home/stew/bin/pylog.py[953165]: warning如果您真的想防止記錄特定級別，請參閱
man systemd.exec：LogLevelMax= Configures filtering by log level of log messages generated by this unit. Takes a syslog log level, one of emerg (lowest log level, only highest priority messages), alert, crit, err, warning, notice, info, debug (highest log level, also lowest priority messages). See syslog(3) for details. By default no filtering is applied (i.e. the default maximum log level is debug). Use this option to configure the logging system to drop log messages of a specific service above the specified level. For example, set LogLevelMax=info in order to turn off debug logging of a particularly chatty unit. Note that the configured level is applied to any log messages written by any of the processes belonging to this unit, as well as any log messages written by the system manager process (PID 1) in reference to this unit, sent via any supported logging protocol. The filtering is applied early in the logging pipeline, before any kind of further processing is done. Moreover, messages which pass through this filter successfully might still be dropped by filters applied at a later stage in the logging subsystem. For example, MaxLevelStore= configured in journald.conf(5) might prohibit messages of higher log levels to be stored on disk, even though the per-unit LogLevelMax= permitted it to be processed.
man journal.conf. 這有：MaxLevelStore= Controls the maximum log level of messages that are stored in the journal. As argument, takes one of "emerg", "alert", "crit", "err", "warning", "notice", "info", "debug", or integer values in the range of 0–7 (corresponding to the same levels). Messages equal or below the log level specified are stored/forwarded, messages above are dropped. Defaults to "debug" to ensure that the all messages are stored in the journal and forwarded to syslog. These settings may be overridden at boot time with the kernel command line options "systemd.journald.max_level_store="但是這些都不能實時配置。對於實時配置，絕對只是記錄所有內容並依賴過濾器來讀取。