在我的所有 Red Hat Linux 机器版本 7.2 上，我们看到 systemd-tmpfiles-clean.service 处于非活动状态：
systemctl status systemd-tmpfiles-clean.service
● systemd-tmpfiles-clean.service - Cleanup of Temporary Directories
Loaded: loaded (/usr/lib/systemd/system/systemd-tmpfiles-clean.service; static; vendor preset: disabled)
Active: inactive (dead) since Wed 2018-12-19 14:47:14 UTC; 12min ago
Docs: man:tmpfiles.d(5)
man:systemd-tmpfiles(8)
Process: 34231 ExecStart=/usr/bin/systemd-tmpfiles --clean (code=exited, status=0/SUCCESS)
Main PID: 34231 (code=exited, status=0/SUCCESS)
Dec 19 14:47:14 master02.uridns.com systemd[1]: Starting Cleanup of Temporary Directories...
Dec 19 14:47:14 master02.uridns.com systemd[1]: Started Cleanup of Temporary Directories.
奇怪的是我们看到了下面的文件和文件夹/tmp，而且似乎每隔一段时间就会进行清理。
我在 crontab 或 cronjob 上搜索，但没有找到其他清理工作。
我在这里错过了什么吗？
尽管服务处于非活动状态，是否有可能每隔几周进行一次清理？
systemctl enable systemd-tmpfiles-clean.service
The unit files have no [Install] section. They are not meant to be enabled
using systemctl.
Possible reasons for having this kind of units are:
1) A unit may be statically enabled by being symlinked from another unit's
.wants/ or .requires/ directory.
2) A unit's purpose may be to act as a helper for some other unit which has
a requirement dependency on it.
3) A unit may be started when needed via activation (socket, path, timer,
D-Bus, udev, scripted systemctl call, ...).
我们还看到了一些非常旧的文件夹，例如
ls -ltr
total 137452
drwxr-xr-x 3 root root 33 Jun 13 2017 Tools
drwx--x--x 3 root root 16 Oct 12 09:33 systemd-private-74982d8a24254a1d8b8ec3b5c0d80a9b-httpd.service-QZqGLA
drwx--x--x 3 root root 16 Oct 12 10:02 systemd-private-74982d8a24254a1d8b8ec3b5c0d80a9b-rtkit-daemon.service-BTcGY1
drwx--x--x 3 root root 16 Oct 12 10:02 systemd-private-74982d8a24254a1d8b8ec3b5c0d80a9b-vmtoolsd.service-mQ1SXc
drwxr-xr-x 2 ambari ambari 18 Oct 12 12:02 hsperfdata_ambari
drwx--x--x 3 root root 16 Oct 12 12:17 systemd-private-74982d8a24254a1d8b8ec3b5c0d80a9b-cups.service-PnKaq8
drwx--x--x 3 root root 16 Oct 12 12:17 systemd-private-74982d8a24254a1d8b8ec3b5c0d80a9b-colord.service-DNn470
-rwxr-xr-x 1 root root 83044 Nov 18 17:27 Spark_Thrift.log
drwxr-xr-x 2 zookeeper hadoop 18 Nov 18 17:28 hsperfdata_zookeeper
-rwxr-xr-x 1 root root 379 Nov 18 17:37 requests.txt
-rwxr-xr-x 1 root root 137348 Nov 22 14:50 pp
-rwxr-xr-x 1 root root 344 Nov 26 15:24 yy
prwx--x--x 1 root root 0 Nov 29 21:26 hogsuspend
-rwxr-xr-x 1 root root 1032 Dec 3 10:55 aa
从我的机器：
more /lib/systemd/system/systemd-tmpfiles-clean.timer
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
[Unit]
Description=Daily Cleanup of Temporary Directories
Documentation=man:tmpfiles.d(5) man:systemd-tmpfiles(8)
[Timer]
OnBootSec=15min
OnUnitActiveSec=1d
规则是：
more /usr/lib/tmpfiles.d/tmp.conf
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
# See tmpfiles.d(5) for details
# Clear tmp directories separately, to make them easier to override
v /tmp 1777 root root 10d
v /var/tmp 1777 root root 30d
# Exclude namespace mountpoints created with PrivateTmp=yes
x /tmp/systemd-private-%b-*
X /tmp/systemd-private-%b-*/tmp
x /var/tmp/systemd-private-%b-*
X /var/tmp/systemd-private-%b-*/tmp
答案1
您可以询问 systemd 单元的触发器是什么：
systemctl show -p TriggeredBy systemd-tmpfiles-clean
这将表明该systemd-tmpfiles-clean服务是由systemd-tmpfiles-clean.timer计时器触发的。其定义为
# SPDX-License-Identifier: LGPL-2.1+
#
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
[Unit]
Description=Daily Cleanup of Temporary Directories
Documentation=man:tmpfiles.d(5) man:systemd-tmpfiles(8)
[Timer]
OnBootSec=15min
OnUnitActiveSec=1d
因此，该服务每天运行，并根据tmpfiles.d配置清理目录。有关详细信息，请参阅相关的手册页。
答案2
systemd-tmpfiles-clean.service是由 发起的systemd-tmpfiles-clean.timer。您可以使用 检查计时器systemctl list-timers。
至少在 Ubuntu 16.04 上，systemd-tmpfiles-clean.timer定义为
# Use `systemctl cat systemd-tmpfiles-clean.timer` to get your corresponding file
#
# /lib/systemd/system/systemd-tmpfiles-clean.timer
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
[Unit]
Description=Daily Cleanup of Temporary Directories
Documentation=man:tmpfiles.d(5) man:systemd-tmpfiles(8)
[Timer]
OnBootSec=15min
OnUnitActiveSec=1d
因此，计时器将systemd-tmpfiles-clean.service在启动后 15 分钟启动，之后每 24 小时启动一次。
有关详细信息，请参阅systemd.timer(5)、systemd.service(5)和systemd.unit(5)。
答案3
这里大多数描述的问题是，它们不包括如何使用它不仅删除文件，还删除文件夹，以及文件夹内的所有子文件夹（包括文件）：
例如/home/user/.cache/：您如何能够告诉工具删除/.cache/folder1/subfolder1&folder2/subfolder1等中的所有文件夹？
它给我一个错误，指出执行命令时文件夹不为空，/.cache/*例如：
# Delete User Space Temp Files
r /home/user/.cache/*
正在执行：
# env SYSTEMD_LOG_LEVEL=debug systemd-tmpfiles --remove
显示错误并且实际上不会删除除顶部文件夹中的文件之外的任何内容。