Linux下关于/tmp目录的清理规则

本文将介绍Linux下/tmp目录的清理规则，rhel6和rhel7将以完全不同的两种方式进行清理。

RHEL6

tmpwatch命令

tmpwatch 是专门用于解决“删除 xxx天没有被访问/修改过的文件”这样需求的命令。

安装：

[root@sam01 ~]# yum install tmpwatch.x86_64

使用：

man tmpwatch

tmpwatch  -  removes files which haven't been accessed for a period of time.

By  default, tmpwatch dates files by their atime (access time), not their mtime (modification time).

The  time  parameter  defines the threshold for removing files.
If the file has not been accessed for time, the file is removed.
The time  argument is a number with an optional single-character suffix specifying the units: m for minutes, h for hours, d for  days.
If no suffix is specified, time is in hours.

   -u, --atime
          Make the decision about deleting a file based on the  file's
          atime (access time). This is the default.

          Note  that  the periodic updatedb file system scans keep the
          atime of directories recent.

   -m, --mtime
          Make the decision about deleting a file based on the  file's
          mtime (modification time) instead of the atime.

   -c, --ctime
          Make  the decision about deleting a file based on the file's
          ctime (inode change time) instead of the atime; for directo‐
          ries, make the decision based on the mtime.

   -M, --dirmtime
          Make  the  decision  about deleting a directory based on the
          directory's mtime (modification time) instead of the  atime;
          completely ignore atime for directories.

举例： （清除/tmp目录下30天没有被访问文件）

[root@sam01 ~]# tmpwatch --atime 30d /tmp

RHEL7

systemd-tmpfiles-clean.service服务

服务： systemd-tmpfiles-clean.service

服务何时被执行呢？

Linux下该服务的执行可以根据systemd-tmpfiles-clean.timer进行管理

[root@sam01 ~]# cat /usr/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() man:systemd-tmpfiles()

[Timer]
OnBootSec=15min
OnUnitActiveSec=1d

# OnBootSec 表示相对于机器被启动的时间点
# 表示相对于匹配单元(本标签下Unit=指定的单元)最后一次被启动的时间点

上述配置文件表示两种情况会执行该服务

1. 开机15分钟执行服务
2. 距离上次执行该服务1天后执行服务

服务如何执行呢？

[root@sam01 ~]# cat /usr/lib/systemd/system/systemd-tmpfiles-clean.service
#  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=Cleanup of Temporary Directories
Documentation=man:tmpfiles.d() man:systemd-tmpfiles()
DefaultDependencies=no
Conflicts=shutdown.target
After=systemd-readahead-collect.service systemd-readahead-replay.service local-fs.target time-sync.target
Before=shutdown.target

[Service]
Type=oneshot
ExecStart=/usr/bin/systemd-tmpfiles --clean
IOSchedulingClass=idle

# Type=oneshot 这一选项适用于只执行一项任务、随后立即退出的服务
# 命令文件 /usr/bin/systemd-tmpfiles
# 命令参数 --clean
# 通过定期执行 /usr/bin/systemd-tmpfiles --clean 完成清理

命令： /usr/bin/systemd-tmpfiles

[root@sam01 ~]# /usr/bin/systemd-tmpfiles --help
systemd-tmpfiles [OPTIONS...] [CONFIGURATION FILE...]

Creates, deletes and cleans up volatile and temporary files and directories.

  -h --help                 Show this help
     --version              Show package version
     --create               Create marked files/directories
     --clean                Clean up marked directories
     --remove               Remove marked files/directories
     --boot                 Execute actions only safe at boot
     --prefix=PATH          Only apply rules with the specified prefix
     --exclude-prefix=PATH  Ignore rules with the specified prefix
     --root=PATH            Operate on an alternate filesystem root

# --clean 将会清理被标记的文件目录

哪些目录被标记，又是什么样的标记呢？

定义在配置文件/usr/lib/tmpfiles.d/tmp.conf中

配置文件： /usr/lib/tmpfiles.d/tmp.conf

[root@sam01 ~]# cat /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() for details

# Clear tmp directories separately, to make them easier to override
v /tmp  root root 10d
v /var/tmp  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

x

在根据"寿命"字段清理过期文件时， 忽略指定的路径及该路径下的所有内容。 可以在"路径"字段中使用shell风格的通配符。 注意，这个保护措施对 r 与 R 无效。

X

在根据"寿命"字段清理过期文件时， 仅忽略指定的路径自身而不包括该路径下的其他内容。 可以在"路径"字段中使用shell风格的通配符。 注意，这个保护措施对 r 与 R 无效。

上述配置表示：

1. 清理/tmp目录超过10天的内容，但是匹配/tmp/systemd-private-%b-*的目录及其路径下的全部内容会被保留

2. 清理/var/tmp目录超过30天的内容，但是匹配/var/tmp/systemd-private-%b-*的目录及其路径下的全部内容被保留

总结

1. RHEL6 根据文件的访问时间等条件使用tmpwatch命令进行/tmp目录的清理，可以使用crond daemon进行定期执行

2. RHEL7 根据服务systemd-tmpfiles-clean.service 进行临时文件的清理，清理规则定义在配置文件/usr/lib/tmpfiles.d/tmp.conf，调用命令为/usr/bin/systemd-tmpfiles --clean，执行时间依靠systemd-tmpfiles-clean.timer进行管理