``` Systemd 统一管理所有 Unit 的启动日志。带来的好处就是 ，可以只用journalctl一个命令，查看所有日志（内核日志和 应用日志）。 日志的配置文件/etc/systemd/journald.conf ``` ## journalctl用法 ### 查看所有日志（默认情况下 ，只保存本次启动的日志） ``` journalctl ``` ## 查看内核日志（不显示应用日志） ``` journalctl -k ``` ## 查看系统本次启动的日志 ``` journalctl -b ``` ## 按服务 ``` journalctl -u httpd.service ``` ## 按进程、用户或群组ID ``` journalctl _PID=8088 ``` ## 输出格式 ``` root@cn-office-crm-qa-all-k8s02:~# journalctl -u mongod -o json-pretty { "__CURSOR" : "s=bca3fda678194adf93b185e09a97c34b;i=2bb;b=a6efcf69186444a7ac50e6d46541ff28;m=3f1d8c8;t=5c50e9f6baf2d;x=9afba0039965fae1", "__REALTIME_TIMESTAMP" : "1624041478401837", "__MONOTONIC_TIMESTAMP" : "66181320", "_BOOT_ID" : "a6efcf69186444a7ac50e6d46541ff28", "_MACHINE_ID" : "38d5d3255ee14f5c9e68eaf9270c4804", "_HOSTNAME" : "cn-office-crm-qa-all-k8s02", "PRIORITY" : "6", "SYSLOG_FACILITY" : "3", "SYSLOG_IDENTIFIER" : "systemd", "_UID" : "0", "_GID" : "0", "_SELINUX_CONTEXT" : "unconfined\n", "_TRANSPORT" : "journal", "_PID" : "1", "_COMM" : "systemd", "_EXE" : "/lib/systemd/systemd", "_CMDLINE" : "/sbin/init", "_CAP_EFFECTIVE" : "3fffffffff", "_SYSTEMD_CGROUP" : "/init.scope", "_SYSTEMD_UNIT" : "init.scope", "_SYSTEMD_SLICE" : "-.slice", "CODE_FILE" : "../src/core/job.c", "CODE_LINE" : "842", "CODE_FUNC" : "job_log_status_message", "JOB_TYPE" : "start", "JOB_RESULT" : "done", "MESSAGE_ID" : "39f53479d3a045ac8e11786248231fbf", "MESSAGE" : "Started MongoDB Database Server.", "UNIT" : "mongod.service", "INVOCATION_ID" : "e60677f45d794c3797f7686cda26a86e", "_SOURCE_REALTIME_TIMESTAMP" : "1624041478401812" } ```