How to troubleshoot Systemd service startup ordering issues

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文章标签： Systemd service startup ordering

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本文介绍如何通过systemd-bootchart服务获取精确的服务启动时间和顺序，以解决在Red Hat Enterprise Linux 7.3+环境中确定服务实际启动顺序的问题。通过启用并重启系统，可以生成SVG图像，清晰展示毫秒级的系统服务启动过程。

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SOLUTION 已验证 - 已更新 2017年七月13日02:53 -

English

环境

Red Hat Enterprise Linux 7.3+
- Systemd

问题

What command can I use to determine the "literal/actual" start-up sequence of service units (get date/time) and/or
which log files should I check?
I know I can use systemd-analyze to get dependency info, but I want to know that actual start-up times/order/logs
of specific services.

决议

1) Enable the "systemd-bootchart" service.

Raw

    # systemctl enable systemd-bootchart

2) Restart the system.

Raw

    # systemctl reboot

3) Review the resulting /run/log/bootchart*.svg file for the boot process to verify ordering of service startup.

Raw

    # systemctl status systemd-bootchart -l
    ● systemd-bootchart.service - Boot Process Profiler
       Loaded: loaded (/usr/lib/systemd/system/systemd-bootchart.service; enabled; vendor preset: disabled)
       Active: inactive (dead) since Fri 2017-03-31 11:23:05 EDT; 3s ago
         Docs: man:systemd-bootchart.service(1)
           man:bootchart.conf(5)
      Process: 468 ExecStart=/usr/lib/systemd/systemd-bootchart -r (code=exited, status=0/SUCCESS)
     Main PID: 468 (code=exited, status=0/SUCCESS)

    Mar 31 11:23:05 host.example.com systemd-bootchart[468]: Bootchart created: /run/log/bootchart-20170331-1122.svg
    Mar 31 11:23:05 host.example.com systemd-bootchart[468]: systemd-bootchart wrote /run/log/bootchart-20170331-1122.svg

Should further assistance be needed, please open a case with Red Hat support and provide the following:

A full description of the issue being encountered
A sosreport of the system
The resulting bootchart-*.svg file

根源

When attempting to implement an ordering dependency within Systemd services, the exact ordering of operations can be difficult to infer. The system logs generally provide timestamps related to the operation, but can be difficult to decipher. The systemd-bootchart utility yields a Scalable Vector Graphic (SVG) image that yields millisecond resolution of system services.