临时目录/tmp

Linux有两个公知的临时目录：/tmp与/var/tmp

这两个目录被用户用于存储临时性的文件，亦经常被读写用户存储临时性数据。

两个目录没有本质上的区别，最根本的区别仅仅是系统对其中文件清理的默认时间配置不一致。

/tmp 目录默认清理10天未用的文件，系统重启会清空目录。

/var/tmp 目录默认清理30天未用的文件。

CentOS 6系统在/etc/cron.daily/tmpwatch

[root@db01 ~]# 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(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

如果/tmp目录被误删除了也没事，重建就可以了

[root@db01 ~]# mkdir -p /tmp
[root@db01 ~]# chmod a+rwx,o+t /tmp
[root@db01 ~]# ls -ld /tmp
drwxrwxrwt. 9 root root 4096 Jan 13 03:47 /tmp