Linux任务计划at

一Linux任务计划介绍

Linux任务计划、周期性任务执行
at：未来的某时间点执行一次任务
batch：系统自行选择空闲时间去执行此处指定的任务
cron：周期性运行某任务

二at计划任务

执行方式：
交互式，输入重定向，at –f 文件
依赖与atd服务,需要启动才能实现at任务，at队列存放在/var/spool/at目录中

（一）安装at包

最小化安装默认是没有安装的，光盘自带的包

[root@centos72 ~]# yum  install  at  -y

Loaded plugins: fastestmirror

Loading mirror speeds from cached hostfile

Resolving Dependencies

--> Running transaction check

---> Package at.x86_64 0:3.1.13-23.el7 will be installed

--> Finished Dependency Resolution

Dependencies Resolved

========================================================================================================

 Package             Arch                    Version                        Repository             Size

========================================================================================================

Installing:

 at                  x86_64                  3.1.13-23.el7                  base                   51 k

Transaction Summary

========================================================================================================

Install  1 Package

Total download size: 51 k

Installed size: 95 k

Downloading packages:

Running transaction check

Running transaction test

Transaction test succeeded

Running transaction

  Installing : at-3.1.13-23.el7.x86_64                                                              1/1

  Verifying  : at-3.1.13-23.el7.x86_64                                                              1/1 

Installed:

  at.x86_64 0:3.1.13-23.el7                                                                             

Complete!

查看包的介绍

[root@centos72 ~]# rpm  -q at

at-3.1.13-23.el7.x86_64

[root@centos72 ~]# rpm  -qi  at

Name        : at

Version     : 3.1.13

Release     : 23.el7

Architecture: x86_64

Install Date: Mon 29 Jul 2019 04:42:51 PM CST

Group       : System Environment/Daemons

Size        : 97561

License     : GPLv3+ and GPLv2+ and ISC and MIT and Public Domain

Signature   : RSA/SHA256, Wed 25 Apr 2018 06:52:49 PM CST, Key ID 24c6a8a7f4a80eb5

Source RPM  : at-3.1.13-23.el7.src.rpm

Build Date  : Wed 11 Apr 2018 08:13:35 AM CST

Build Host  : x86-01.bsys.centos.org

Relocations : (not relocatable)

Packager    : CentOS BuildSystem <http://bugs.centos.org>

Vendor      : CentOS

URL         : http://ftp.debian.org/debian/pool/main/a/at

Summary     : Job spooling tools

Description :

At and batch read commands from standard input or from a specified

file. At allows you to specify that a command will be run at a

particular time. Batch will execute commands when the system load

levels drop to a particular level. Both commands use user's shell.

You should install the at package if you need a utility for

time-oriented job control. Note: If it is a recurring job that will

need to be repeated at the same time every day/week, etc. you should

use crontab instead.

6版本

[root@centos65 ~]#  rpm -q  at

at-3.1.10-48.el6.x86_64

[root@centos65 ~]#  rpm -qi  at

Name        : at                           Relocations: (not relocatable)

Version     : 3.1.10                            Vendor: CentOS

Release     : 48.el6                        Build Date: Fri 20 Feb 2015 12:23:33 AM CST

Install Date: Wed 23 Jan 2019 05:30:47 PM CST      Build Host: c6b8.bsys.dev.centos.org

Group       : System Environment/Daemons    Source RPM: at-3.1.10-48.el6.src.rpm

Size        : 94221                            License: GPLv2+

Signature   : RSA/SHA1, Fri 20 Feb 2015 12:34:52 AM CST, Key ID 0946fca2c105b9de

Packager    : CentOS BuildSystem <http://bugs.centos.org>

URL         : http://ftp.debian.org/debian/pool/main/a/at

Summary     : Job spooling tools

Description :

At and batch read commands from standard input or from a specified

file. At allows you to specify that a command will be run at a

particular time. Batch will execute commands when the system load

levels drop to a particular level. Both commands use user's shell.

You should install the at package if you need a utility for

time-oriented job control. Note: If it is a recurring job that will

need to be repeated at the same time every day/week, etc. you should

use crontab instead.

（二）at包的组成

[root@centos72 ~]# rpm -ql  at

/etc/at.deny

/etc/pam.d/atd

/etc/sysconfig/atd

/usr/bin/at

/usr/bin/atq

/usr/bin/atrm

/usr/bin/batch

/usr/lib/systemd/system/atd.service

/usr/sbin/atd

/usr/sbin/atrun

/usr/share/doc/at-3.1.13

/usr/share/doc/at-3.1.13/ChangeLog

/usr/share/doc/at-3.1.13/Copyright

/usr/share/doc/at-3.1.13/Problems

/usr/share/doc/at-3.1.13/README

/usr/share/doc/at-3.1.13/timespec

/usr/share/man/man1/at.1.gz

/usr/share/man/man1/atq.1.gz

/usr/share/man/man1/atrm.1.gz

/usr/share/man/man1/batch.1.gz

/usr/share/man/man5/at.allow.5.gz

/usr/share/man/man5/at.deny.5.gz

/usr/share/man/man8/atd.8.gz

/usr/share/man/man8/atrun.8.gz

/var/spool/at

/var/spool/at/.SEQ

/var/spool/at/spool

服务存放位置/etc/rc.d/init.d/atd

运行的程序/usr/sbin/atd

[root@centos65 ~]#  rpm -ql  at

/etc/at.deny

/etc/pam.d/atd

/etc/rc.d/init.d/atd

/etc/sysconfig/atd

/usr/bin/at

/usr/bin/atq

/usr/bin/atrm

/usr/bin/batch

/usr/lib64/pm-utils/sleep.d/56atd

/usr/sbin/atd

/usr/sbin/atrun

/usr/share/doc/at-3.1.10

/usr/share/doc/at-3.1.10/ChangeLog

/usr/share/doc/at-3.1.10/Copyright

/usr/share/doc/at-3.1.10/Problems

/usr/share/doc/at-3.1.10/README

/usr/share/doc/at-3.1.10/timespec

/usr/share/man/man1/at.1.gz

/usr/share/man/man1/atq.1.gz

/usr/share/man/man1/atrm.1.gz

/usr/share/man/man1/batch.1.gz

/usr/share/man/man5/at.allow.5.gz

/usr/share/man/man8/atd.8.gz

/usr/share/man/man8/atrun.8.gz

/var/spool/at

/var/spool/at/.SEQ

/var/spool/at/spool

查看开机是否自启

因为是比较基础的服务，开机一般自启

[root@centos72 ~]# systemctl is-enabled  atd

enabled

[root@centos72 ~]# systemctl is-enabled  atd.service

enabled
[root@centos65 ~]# chkconfig  --list  atd

atd                0:off    1:off    2:off    3:on    4:on    5:on    6:off

[root@centos65 ~]# runlevel

N

服务调用了程序/usr/sbin/atd

[root@centos72 ~]# systemctl status  atd.service

● atd.service - Job spooling tools

   Loaded: loaded (/usr/lib/systemd/system/atd.service; enabled; vendor preset: enabled)

   Active: inactive (dead)

[root@centos72 ~]# systemctl start   atd.service

[root@centos72 ~]# systemctl status  atd.service

● atd.service - Job spooling tools

   Loaded: loaded (/usr/lib/systemd/system/atd.service; enabled; vendor preset: enabled)

   Active: active (running) since Tue 2019-05-21 09:28:49 CST; 1s ago

 Main PID: 2710 (atd)

   CGroup: /system.slice/atd.service

           └─2710 /usr/sbin/atd -f

May 21 09:28:49 centos72.huawei.com systemd[1]: Started Job spooling tools.

May 21 09:28:49 centos72.huawei.com systemd[1]: Starting Job spooling tools...

进程编号是2710

[root@centos72 ~]# ps aux  | grep  2710

root       2710  0.0  0.0  25904   936 ?        Ss   09:28   0:00 /usr/sbin/atd -f

root       2719  0.0  0.0 112704   972 pts/0    S+   09:30   0:00 grep --color=auto

（三）常用选项

-V 显示版本信息:
-l: 列出指定队列中等待运行的作业；相当于atq
-d: 删除指定的作业；相当于atrm
-c: 查看具体作业任务
-f /path/from/somefile：从指定的文件中读取任务
-m:当任务被完成之后，将给用户发送邮件，即使没有标准输出
注意：作业执行命令的结果中的标准输出和错误以邮件通知给相关用户

（四）at时间格式

HH:MM 02:00
在今日的 HH:MM 进行，若该时刻已过，则明天此时执行任务
HH:MM YYYY-MM-DD 02:00 2018-01-08
规定在某年某月的某一天的特殊时刻进行该项任务
HH:MM[am|pm] [Month] [Date]
04pm March 17
17:20 tomorrow
HH:MM[am|pm] + number [minutes|hours|days|weeks]
在某个时间点再加几个时间后才进行该项任务
now + 5 minutes
02pm + 3 days

三创建at计划任务广播时间

（一）前期准备

1时间同步，虚拟机的时间和宿主机的时间、网络时间要一致

2关闭防火墙

3关闭selinux

（二）创建at计划任务

按ctrl+d保存

[root@centos72 ~]# at  10:00

at> wall 10:00  clock

at> <EOT>

job 1 at Tue May 21 10:00:00 2019

[root@centos72 ~]# at -l

1    Tue May 21 10:00:00 2019 = root

[root@centos72 ~]#

Broadcast message from root@centos72.huawei.com (Tue May 21 10:00:01 2019):

10:00 clock

在创建计划任务完成之后就会写到文件里面了

[root@centos72 ~]# at  10:10

at> wall 10:10  clock

at> <EOT>

job 2 at Tue May 21 10:10:00 2019

[root@centos72 ~]# at -l

2    Tue May 21 10:10:00 2019 a root

[root@centos72 ~]# ls  /var/spool/at  -l

total 4

-rwx------. 1 root root 2806 May 21 10:04 a00002018c52a2

drwx------. 2 root root    6 May 21 10:00 spool

执行完了任务就会把相应的文件删除了

[root@centos72 ~]# cat /var/spool/at/a00002018c52a2

#!/bin/sh

# atrun uid=0 gid=0

# mail root 0

umask 22

XDG_SESSION_ID=79; export XDG_SESSION_ID

HOSTNAME=centos72.huawei.com; export HOSTNAME

SELINUX_ROLE_REQUESTED=; export SELINUX_ROLE_REQUESTED

SHELL=/bin/bash; export SHELL

HISTSIZE=1000; export HISTSIZE

SSH_CLIENT=192.168.137.1\ 49197\ 22; export SSH_CLIENT

SELINUX_USE_CURRENT_RANGE=; export SELINUX_USE_CURRENT_RANGE

SSH_TTY=/dev/pts/0; export SSH_TTY

USER=root; export USER

LS_COLORS=rs=0:di=01\;34:ln=01\;36:mh=00:pi=40\;33:so=01\;35:do=01\;35:bd=40\;33\;01:cd=40\;33\;01:or=40\;31\;01:mi=01\;05\;37\;41:su=37\;41:sg=30\;43:ca=30\;41:tw=30\;42:ow=34\;42:st=37\;44:ex=01\;32:\*.tar=01\;31:\*.tgz=01\;31:\*.arc=01\;31:\*.arj=01\;31:\*.taz=01\;31:\*.lha=01\;31:\*.lz4=01\;31:\*.lzh=01\;31:\*.lzma=01\;31:\*.tlz=01\;31:\*.txz=01\;31:\*.tzo=01\;31:\*.t7z=01\;31:\*.zip=01\;31:\*.z=01\;31:\*.Z=01\;31:\*.dz=01\;31:\*.gz=01\;31:\*.lrz=01\;31:\*.lz=01\;31:\*.lzo=01\;31:\*.xz=01\;31:\*.bz2=01\;31:\*.bz=01\;31:\*.tbz=01\;31:\*.tbz2=01\;31:\*.tz=01\;31:\*.deb=01\;31:\*.rpm=01\;31:\*.jar=01\;31:\*.war=01\;31:\*.ear=01\;31:\*.sar=01\;31:\*.rar=01\;31:\*.alz=01\;31:\*.ace=01\;31:\*.zoo=01\;31:\*.cpio=01\;31:\*.7z=01\;31:\*.rz=01\;31:\*.cab=01\;31:\*.jpg=01\;35:\*.jpeg=01\;35:\*.gif=01\;35:\*.bmp=01\;35:\*.pbm=01\;35:\*.pgm=01\;35:\*.ppm=01\;35:\*.tga=01\;35:\*.xbm=01\;35:\*.xpm=01\;35:\*.tif=01\;35:\*.tiff=01\;35:\*.png=01\;35:\*.svg=01\;35:\*.svgz=01\;35:\*.mng=01\;35:\*.pcx=01\;35:\*.mov=01\;35:\*.mpg=01\;35:\*.mpeg=01\;35:\*.m2v=01\;35:\*.mkv=01\;35:\*.webm=01\;35:\*.ogm=01\;35:\*.mp4=01\;35:\*.m4v=01\;35:\*.mp4v=01\;35:\*.vob=01\;35:\*.qt=01\;35:\*.nuv=01\;35:\*.wmv=01\;35:\*.asf=01\;35:\*.rm=01\;35:\*.rmvb=01\;35:\*.flc=01\;35:\*.avi=01\;35:\*.fli=01\;35:\*.flv=01\;35:\*.gl=01\;35:\*.dl=01\;35:\*.xcf=01\;35:\*.xwd=01\;35:\*.yuv=01\;35:\*.cgm=01\;35:\*.emf=01\;35:\*.axv=01\;35:\*.anx=01\;35:\*.ogv=01\;35:\*.ogx=01\;35:\*.aac=01\;36:\*.au=01\;36:\*.flac=01\;36:\*.mid=01\;36:\*.midi=01\;36:\*.mka=01\;36:\*.mp3=01\;36:\*.mpc=01\;36:\*.ogg=01\;36:\*.ra=01\;36:\*.wav=01\;36:\*.axa=01\;36:\*.oga=01\;36:\*.spx=01\;36:\*.xspf=01\;36:; export LS_COLORS

MAIL=/var/spool/mail/root; export MAIL

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin; export PATH

PWD=/root; export PWD

LANG=en_US.UTF-8; export LANG

SELINUX_LEVEL_REQUESTED=; export SELINUX_LEVEL_REQUESTED

HISTCONTROL=ignoredups; export HISTCONTROL

SHLVL=1; export SHLVL

HOME=/root; export HOME

LOGNAME=root; export LOGNAME

SSH_CONNECTION=192.168.137.1\ 49197\ 192.168.137.72\ 22; export SSH_CONNECTION

LESSOPEN=\|\|/usr/bin/lesspipe.sh\ %s; export LESSOPEN

XDG_RUNTIME_DIR=/run/user/0; export XDG_RUNTIME_DIR

cd /root || {

     echo 'Execution directory inaccessible' >&2

     exit 1

}

${SHELL:-/bin/sh} << 'marcinDELIMITER0a4474a2'

wall 10:10  clock

marcinDELIMITER0a4474a2

注意在计划任务里面，所有的标准输出不会在屏幕上显示，而是放到了邮件里面

如果是广播就会在所有的终端都显示

[root@centos72 ~]#

Broadcast message from root@centos72.huawei.com (Tue May 21 10:10:00 2019):

10:10 clock

四at选项示例

（一）-l: 列出指定队列中等待运行的作业；相当于atq

定义计划任务，并且是打印标准输出的

[root@centos72 ~]# at  10:15

at> hostname

at> ls

at> pwd

at> who

at> <EOT>

job 3 at Tue May 21 10:15:00

安装邮件服务

[root@centos72 ~]# yum -y install mailx

Loaded plugins: fastestmirror

Loading mirror speeds from cached hostfile

file:///mnt/repodata/repomd.xml: [Errno 14] curl#37 - "Couldn't open file /mnt/repodata/repomd.xml"

Trying other mirror.

Resolving Dependencies

--> Running transaction check

---> Package mailx.x86_64 0:12.5-19.el7 will be installed

--> Finished Dependency Resolution

Dependencies Resolved

========================================================================================================

 Package              Arch                  Version                     Repository                 Size

========================================================================================================

Installing:

 mailx                x86_64                12.5-19.el7                 ali-centos                245 k

Transaction Summary

========================================================================================================

Install  1 Package

Total download size: 245 k

Installed size: 466 k

Downloading packages:

mailx-12.5-19.el7.x86_64.rpm                                                     | 245 kB  00:00:00

Running transaction check

Running transaction test

Transaction test succeeded

Running transaction

  Installing : mailx-12.5-19.el7.x86_64                                                             1/1

  Verifying  : mailx-12.5-19.el7.x86_64                                                             1/1 

Installed:

  mailx.x86_64 0:12.5-19.el7                                                                            

Complete!

在邮件里面显示了计划任务的内容

[root@centos72 ~]# mail

No mail for root

[root@centos72 ~]# mail

Heirloom Mail version 12.5 7/5/10.  Type ? for help.

"/var/spool/mail/root": 1 message 1 new

>N  1 root                  Tue May 21 10:15  35/727   "Output from your job        3"

& 1

Message  1:

From root@centos72.huawei.com  Tue May 21 10:15:00 2019

Return-Path: <root@centos72.huawei.com>

X-Original-To: root

Delivered-To: root@centos72.huawei.com

Subject: Output from your job        3

To: root@centos72.huawei.com

Date: Tue, 21 May 2019 10:15:00 +0800 (CST)

From: root@centos72.huawei.com (root)

Status: R

centos72.huawei.com

1.txt

2.txt

3.txt

4.txt

5.txt

aaa

aa.txt

access_log

anaconda-ks.cfg

aux.txt

f1

f2

f3

f4

f5

grep

nohup.out

x.txt

/root

root     pts/0        2019-05-21 08:42 (192.168.137.1)

root     pts/1        2019-05-21 09:59 (192.168.137.1)

&

At EOF

&

At EOF

&

（二）-c: 查看具体作业任务

如果脚本是在计划任务里面执行最好把标准输出关闭

删除计划任务

[root@centos72 ~]# at  10:30

at> pwd<EOT>

job 4 at Tue May 21 10:30:00 2019

[root@centos72 ~]# at-l

-bash: at-l: command not found

[root@centos72 ~]# at -l

4    Tue May 21 10:30:00 2019 a root

[root@centos72 ~]# at -c  4

#!/bin/sh

# atrun uid=0 gid=0

# mail root 0

umask 22

XDG_SESSION_ID=79; export XDG_SESSION_ID

HOSTNAME=centos72.huawei.com; export HOSTNAME

SELINUX_ROLE_REQUESTED=; export SELINUX_ROLE_REQUESTED

SHELL=/bin/bash; export SHELL

HISTSIZE=1000; export HISTSIZE

SSH_CLIENT=192.168.137.1\ 49197\ 22; export SSH_CLIENT

SELINUX_USE_CURRENT_RANGE=; export SELINUX_USE_CURRENT_RANGE

SSH_TTY=/dev/pts/0; export SSH_TTY

USER=root; export USER

LS_COLORS=rs=0:di=01\;34:ln=01\;36:mh=00:pi=40\;33:so=01\;35:do=01\;35:bd=40\;33\;01:cd=40\;33\;01:or=40\;31\;01:mi=01\;05\;37\;41:su=37\;41:sg=30\;43:ca=30\;41:tw=30\;42:ow=34\;42:st=37\;44:ex=01\;32:\*.tar=01\;31:\*.tgz=01\;31:\*.arc=01\;31:\*.arj=01\;31:\*.taz=01\;31:\*.lha=01\;31:\*.lz4=01\;31:\*.lzh=01\;31:\*.lzma=01\;31:\*.tlz=01\;31:\*.txz=01\;31:\*.tzo=01\;31:\*.t7z=01\;31:\*.zip=01\;31:\*.z=01\;31:\*.Z=01\;31:\*.dz=01\;31:\*.gz=01\;31:\*.lrz=01\;31:\*.lz=01\;31:\*.lzo=01\;31:\*.xz=01\;31:\*.bz2=01\;31:\*.bz=01\;31:\*.tbz=01\;31:\*.tbz2=01\;31:\*.tz=01\;31:\*.deb=01\;31:\*.rpm=01\;31:\*.jar=01\;31:\*.war=01\;31:\*.ear=01\;31:\*.sar=01\;31:\*.rar=01\;31:\*.alz=01\;31:\*.ace=01\;31:\*.zoo=01\;31:\*.cpio=01\;31:\*.7z=01\;31:\*.rz=01\;31:\*.cab=01\;31:\*.jpg=01\;35:\*.jpeg=01\;35:\*.gif=01\;35:\*.bmp=01\;35:\*.pbm=01\;35:\*.pgm=01\;35:\*.ppm=01\;35:\*.tga=01\;35:\*.xbm=01\;35:\*.xpm=01\;35:\*.tif=01\;35:\*.tiff=01\;35:\*.png=01\;35:\*.svg=01\;35:\*.svgz=01\;35:\*.mng=01\;35:\*.pcx=01\;35:\*.mov=01\;35:\*.mpg=01\;35:\*.mpeg=01\;35:\*.m2v=01\;35:\*.mkv=01\;35:\*.webm=01\;35:\*.ogm=01\;35:\*.mp4=01\;35:\*.m4v=01\;35:\*.mp4v=01\;35:\*.vob=01\;35:\*.qt=01\;35:\*.nuv=01\;35:\*.wmv=01\;35:\*.asf=01\;35:\*.rm=01\;35:\*.rmvb=01\;35:\*.flc=01\;35:\*.avi=01\;35:\*.fli=01\;35:\*.flv=01\;35:\*.gl=01\;35:\*.dl=01\;35:\*.xcf=01\;35:\*.xwd=01\;35:\*.yuv=01\;35:\*.cgm=01\;35:\*.emf=01\;35:\*.axv=01\;35:\*.anx=01\;35:\*.ogv=01\;35:\*.ogx=01\;35:\*.aac=01\;36:\*.au=01\;36:\*.flac=01\;36:\*.mid=01\;36:\*.midi=01\;36:\*.mka=01\;36:\*.mp3=01\;36:\*.mpc=01\;36:\*.ogg=01\;36:\*.ra=01\;36:\*.wav=01\;36:\*.axa=01\;36:\*.oga=01\;36:\*.spx=01\;36:\*.xspf=01\;36:; export LS_COLORS

MAIL=/var/spool/mail/root; export MAIL

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin; export PATH

PWD=/root; export PWD

LANG=en_US.UTF-8; export LANG

SELINUX_LEVEL_REQUESTED=; export SELINUX_LEVEL_REQUESTED

HISTCONTROL=ignoredups; export HISTCONTROL

SHLVL=1; export SHLVL

HOME=/root; export HOME

LOGNAME=root; export LOGNAME

SSH_CONNECTION=192.168.137.1\ 49197\ 192.168.137.72\ 22; export SSH_CONNECTION

LESSOPEN=\|\|/usr/bin/lesspipe.sh\ %s; export LESSOPEN

XDG_RUNTIME_DIR=/run/user/0; export XDG_RUNTIME_DIR

cd /root || {

     echo 'Execution directory inaccessible' >&2

     exit 1

}

${SHELL:-/bin/sh} << 'marcinDELIMITER615fc239'

pwd

marcinDELIMITER615fc239

（三）-d: 删除指定的作业；相当于atrm

文件也被删除了

[root@centos72 ~]# atrm   4

[root@centos72 ~]# at -l

[root@centos72 ~]# at -c  4

Cannot find jobid 4

[root@centos72 ~]# ls /var/spool/at

spool

[root@centos72 ~]# ls /var/spool/at  -l

total 0

drwx------. 2 root root 6 May 21 10:15 spool

[root@centos72 ~]#

（四）-V 显示版本信息

显示版本信息，小版本不同，没有多大区别

[root@centos72 ~]# at -V

at version 3.1.13

[root@centos65 ~]#  at -V

at version 3.1.

使用重定向创建脚本

[root@centos65 ~]# at  11:00  <<EOF

> wall noon

> EOF

job 2 at 2019-05-21 11:00

[root@centos65 ~]# at -l

2    2019-05-21 11:00 a root

[root@centos65 ~]# at -c  4

Cannot find jobid 4

[root@centos65 ~]# at -c  2

#!/bin/sh

# atrun uid=0 gid=0

# mail root 0

umask 22

HOSTNAME=centos65.jd.com; export HOSTNAME

SELINUX_ROLE_REQUESTED=; export SELINUX_ROLE_REQUESTED

SHELL=/bin/bash; export SHELL

HISTSIZE=1000; export HISTSIZE

SSH_CLIENT=192.168.137.1\ 56213\ 22; export SSH_CLIENT

SELINUX_USE_CURRENT_RANGE=; export SELINUX_USE_CURRENT_RANGE

SSH_TTY=/dev/pts/1; export SSH_TTY

USER=root; export USER

LS_COLORS=rs=0:di=01\;34:ln=01\;36:mh=00:pi=40\;33:so=01\;35:do=01\;35:bd=40\;33\;01:cd=40\;33\;01:or=40\;31\;01:mi=01\;05\;37\;41:su=37\;41:sg=30\;43:ca=30\;41:tw=30\;42:ow=34\;42:st=37\;44:ex=01\;32:\*.tar=01\;31:\*.tgz=01\;31:\*.arj=01\;31:\*.taz=01\;31:\*.lzh=01\;31:\*.lzma=01\;31:\*.tlz=01\;31:\*.txz=01\;31:\*.zip=01\;31:\*.z=01\;31:\*.Z=01\;31:\*.dz=01\;31:\*.gz=01\;31:\*.lz=01\;31:\*.xz=01\;31:\*.bz2=01\;31:\*.tbz=01\;31:\*.tbz2=01\;31:\*.bz=01\;31:\*.tz=01\;31:\*.deb=01\;31:\*.rpm=01\;31:\*.jar=01\;31:\*.rar=01\;31:\*.ace=01\;31:\*.zoo=01\;31:\*.cpio=01\;31:\*.7z=01\;31:\*.rz=01\;31:\*.jpg=01\;35:\*.jpeg=01\;35:\*.gif=01\;35:\*.bmp=01\;35:\*.pbm=01\;35:\*.pgm=01\;35:\*.ppm=01\;35:\*.tga=01\;35:\*.xbm=01\;35:\*.xpm=01\;35:\*.tif=01\;35:\*.tiff=01\;35:\*.png=01\;35:\*.svg=01\;35:\*.svgz=01\;35:\*.mng=01\;35:\*.pcx=01\;35:\*.mov=01\;35:\*.mpg=01\;35:\*.mpeg=01\;35:\*.m2v=01\;35:\*.mkv=01\;35:\*.ogm=01\;35:\*.mp4=01\;35:\*.m4v=01\;35:\*.mp4v=01\;35:\*.vob=01\;35:\*.qt=01\;35:\*.nuv=01\;35:\*.wmv=01\;35:\*.asf=01\;35:\*.rm=01\;35:\*.rmvb=01\;35:\*.flc=01\;35:\*.avi=01\;35:\*.fli=01\;35:\*.flv=01\;35:\*.gl=01\;35:\*.dl=01\;35:\*.xcf=01\;35:\*.xwd=01\;35:\*.yuv=01\;35:\*.cgm=01\;35:\*.emf=01\;35:\*.axv=01\;35:\*.anx=01\;35:\*.ogv=01\;35:\*.ogx=01\;35:\*.aac=01\;36:\*.au=01\;36:\*.flac=01\;36:\*.mid=01\;36:\*.midi=01\;36:\*.mka=01\;36:\*.mp3=01\;36:\*.mpc=01\;36:\*.ogg=01\;36:\*.ra=01\;36:\*.wav=01\;36:\*.axa=01\;36:\*.oga=01\;36:\*.spx=01\;36:\*.xspf=01\;36:; export LS_COLORS

MAIL=/var/spool/mail/root; export MAIL

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin; export PATH

PWD=/root; export PWD

LANG=en_US.UTF-8; export LANG

SELINUX_LEVEL_REQUESTED=; export SELINUX_LEVEL_REQUESTED

HISTCONTROL=ignoredups; export HISTCONTROL

SHLVL=1; export SHLVL

HOME=/root; export HOME

LOGNAME=root; export LOGNAME

CVS_RSH=ssh; export CVS_RSH

SSH_CONNECTION=192.168.137.1\ 56213\ 192.168.137.65\ 22; export SSH_CONNECTION

LESSOPEN=\|\|/usr/bin/lesspipe.sh\ %s; export LESSOPEN

G_BROKEN_FILENAMES=1; export G_BROKEN_FILENAMES

cd /root || {

     echo 'Execution directory inaccessible' >&2

     exit 1

}

${SHELL:-/bin/sh} << 'marcinDELIMITER6e38cb04'

wall noon

marcinDELIMITER6e38cb04

at是读取键盘输入，echo是打印标准输出

管道的作用就是把前面的标准输出作为后面的标准输入

[root@centos65 ~]# echo   "wall  at jobs"  |  at  11:00

job 3 at 2019-05-21 11:00

[root@centos65 ~]# at -l

2    2019-05-21 11:00 a root

3    2019-05-21 11:00 a root

多条命令放到计划任务里面

添加换行即可

[root@centos65 ~]# echo  -e  "wall at jobs1\nwall^Ct jobs2\nwall at jobs3"  | at  11:00

[root@centos65 ~]# at -l

4    2019-05-21 11:00 a root

2    2019-05-21 11:00 a root

5    2019-05-21 11:00 a root

3    2019-05-21 11:00 a root

[root@centos65 ~]# at  -c  4

#!/bin/sh

# atrun uid=0 gid=0

# mail root 0

umask 22

HOSTNAME=centos65.jd.com; export HOSTNAME

SELINUX_ROLE_REQUESTED=; export SELINUX_ROLE_REQUESTED

SHELL=/bin/bash; export SHELL

HISTSIZE=1000; export HISTSIZE

SSH_CLIENT=192.168.137.1\ 56213\ 22; export SSH_CLIENT

SELINUX_USE_CURRENT_RANGE=; export SELINUX_USE_CURRENT_RANGE

SSH_TTY=/dev/pts/1; export SSH_TTY

USER=root; export USER

LS_COLORS=rs=0:di=01\;34:ln=01\;36:mh=00:pi=40\;33:so=01\;35:do=01\;35:bd=40\;33\;01:cd=40\;33\;01:or=40\;31\;01:mi=01\;05\;37\;41:su=37\;41:sg=30\;43:ca=30\;41:tw=30\;42:ow=34\;42:st=37\;44:ex=01\;32:\*.tar=01\;31:\*.tgz=01\;31:\*.arj=01\;31:\*.taz=01\;31:\*.lzh=01\;31:\*.lzma=01\;31:\*.tlz=01\;31:\*.txz=01\;31:\*.zip=01\;31:\*.z=01\;31:\*.Z=01\;31:\*.dz=01\;31:\*.gz=01\;31:\*.lz=01\;31:\*.xz=01\;31:\*.bz2=01\;31:\*.tbz=01\;31:\*.tbz2=01\;31:\*.bz=01\;31:\*.tz=01\;31:\*.deb=01\;31:\*.rpm=01\;31:\*.jar=01\;31:\*.rar=01\;31:\*.ace=01\;31:\*.zoo=01\;31:\*.cpio=01\;31:\*.7z=01\;31:\*.rz=01\;31:\*.jpg=01\;35:\*.jpeg=01\;35:\*.gif=01\;35:\*.bmp=01\;35:\*.pbm=01\;35:\*.pgm=01\;35:\*.ppm=01\;35:\*.tga=01\;35:\*.xbm=01\;35:\*.xpm=01\;35:\*.tif=01\;35:\*.tiff=01\;35:\*.png=01\;35:\*.svg=01\;35:\*.svgz=01\;35:\*.mng=01\;35:\*.pcx=01\;35:\*.mov=01\;35:\*.mpg=01\;35:\*.mpeg=01\;35:\*.m2v=01\;35:\*.mkv=01\;35:\*.ogm=01\;35:\*.mp4=01\;35:\*.m4v=01\;35:\*.mp4v=01\;35:\*.vob=01\;35:\*.qt=01\;35:\*.nuv=01\;35:\*.wmv=01\;35:\*.asf=01\;35:\*.rm=01\;35:\*.rmvb=01\;35:\*.flc=01\;35:\*.avi=01\;35:\*.fli=01\;35:\*.flv=01\;35:\*.gl=01\;35:\*.dl=01\;35:\*.xcf=01\;35:\*.xwd=01\;35:\*.yuv=01\;35:\*.cgm=01\;35:\*.emf=01\;35:\*.axv=01\;35:\*.anx=01\;35:\*.ogv=01\;35:\*.ogx=01\;35:\*.aac=01\;36:\*.au=01\;36:\*.flac=01\;36:\*.mid=01\;36:\*.midi=01\;36:\*.mka=01\;36:\*.mp3=01\;36:\*.mpc=01\;36:\*.ogg=01\;36:\*.ra=01\;36:\*.wav=01\;36:\*.axa=01\;36:\*.oga=01\;36:\*.spx=01\;36:\*.xspf=01\;36:; export LS_COLORS

MAIL=/var/spool/mail/root; export MAIL

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin; export PATH

PWD=/root; export PWD

LANG=en_US.UTF-8; export LANG

SELINUX_LEVEL_REQUESTED=; export SELINUX_LEVEL_REQUESTED

HISTCONTROL=ignoredups; export HISTCONTROL

SHLVL=1; export SHLVL

HOME=/root; export HOME

LOGNAME=root; export LOGNAME

CVS_RSH=ssh; export CVS_RSH

SSH_CONNECTION=192.168.137.1\ 56213\ 192.168.137.65\ 22; export SSH_CONNECTION

LESSOPEN=\|\|/usr/bin/lesspipe.sh\ %s; export LESSOPEN

G_BROKEN_FILENAMES=1; export G_BROKEN_FILENAMES

cd /root || {

     echo 'Execution directory inaccessible' >&2

     exit 1

}

${SHELL:-/bin/sh} << 'marcinDELIMITER0e859fa1'

wall at jobs1

wall  at jobs2

wall at jobs3

marcinDELIMITER0e859fa1

（五）-f /path/from/somefile：从指定的文件中读取任务

[root@centos65 ~]# cat  >  atjobs.sh

wall jobs1

wall jobs2

[root@centos65 ~]# cat  atjobs.sh

wall jobs1

wall jobs2

[root@centos65 ~]# at  11:10 <  atjobs.sh

job 6 at 2019-05-21 11:10

[root@centos65 ~]# at -l

4    2019-05-21 11:00 a root

2    2019-05-21 11:00 a root

6    2019-05-21 11:10 a root

5    2019-05-21 11:00 a root

3    2019-05-21 11:00 a root
[root@centos65 ~]# at  -c 6

#!/bin/sh

# atrun uid=0 gid=0

# mail root 0

umask 22

HOSTNAME=centos65.jd.com; export HOSTNAME

SELINUX_ROLE_REQUESTED=; export SELINUX_ROLE_REQUESTED

SHELL=/bin/bash; export SHELL

HISTSIZE=1000; export HISTSIZE

SSH_CLIENT=192.168.137.1\ 56213\ 22; export SSH_CLIENT

SELINUX_USE_CURRENT_RANGE=; export SELINUX_USE_CURRENT_RANGE

SSH_TTY=/dev/pts/1; export SSH_TTY

USER=root; export USER

LS_COLORS=rs=0:di=01\;34:ln=01\;36:mh=00:pi=40\;33:so=01\;35:do=01\;35:bd=40\;33\;01:cd=40\;33\;01:or=40\;31\;01:mi=01\;05\;37\;41:su=37\;41:sg=30\;43:ca=30\;41:tw=30\;42:ow=34\;42:st=37\;44:ex=01\;32:\*.tar=01\;31:\*.tgz=01\;31:\*.arj=01\;31:\*.taz=01\;31:\*.lzh=01\;31:\*.lzma=01\;31:\*.tlz=01\;31:\*.txz=01\;31:\*.zip=01\;31:\*.z=01\;31:\*.Z=01\;31:\*.dz=01\;31:\*.gz=01\;31:\*.lz=01\;31:\*.xz=01\;31:\*.bz2=01\;31:\*.tbz=01\;31:\*.tbz2=01\;31:\*.bz=01\;31:\*.tz=01\;31:\*.deb=01\;31:\*.rpm=01\;31:\*.jar=01\;31:\*.rar=01\;31:\*.ace=01\;31:\*.zoo=01\;31:\*.cpio=01\;31:\*.7z=01\;31:\*.rz=01\;31:\*.jpg=01\;35:\*.jpeg=01\;35:\*.gif=01\;35:\*.bmp=01\;35:\*.pbm=01\;35:\*.pgm=01\;35:\*.ppm=01\;35:\*.tga=01\;35:\*.xbm=01\;35:\*.xpm=01\;35:\*.tif=01\;35:\*.tiff=01\;35:\*.png=01\;35:\*.svg=01\;35:\*.svgz=01\;35:\*.mng=01\;35:\*.pcx=01\;35:\*.mov=01\;35:\*.mpg=01\;35:\*.mpeg=01\;35:\*.m2v=01\;35:\*.mkv=01\;35:\*.ogm=01\;35:\*.mp4=01\;35:\*.m4v=01\;35:\*.mp4v=01\;35:\*.vob=01\;35:\*.qt=01\;35:\*.nuv=01\;35:\*.wmv=01\;35:\*.asf=01\;35:\*.rm=01\;35:\*.rmvb=01\;35:\*.flc=01\;35:\*.avi=01\;35:\*.fli=01\;35:\*.flv=01\;35:\*.gl=01\;35:\*.dl=01\;35:\*.xcf=01\;35:\*.xwd=01\;35:\*.yuv=01\;35:\*.cgm=01\;35:\*.emf=01\;35:\*.axv=01\;35:\*.anx=01\;35:\*.ogv=01\;35:\*.ogx=01\;35:\*.aac=01\;36:\*.au=01\;36:\*.flac=01\;36:\*.mid=01\;36:\*.midi=01\;36:\*.mka=01\;36:\*.mp3=01\;36:\*.mpc=01\;36:\*.ogg=01\;36:\*.ra=01\;36:\*.wav=01\;36:\*.axa=01\;36:\*.oga=01\;36:\*.spx=01\;36:\*.xspf=01\;36:; export LS_COLORS

MAIL=/var/spool/mail/root; export MAIL

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin; export PATH

PWD=/root; export PWD

LANG=en_US.UTF-8; export LANG

SELINUX_LEVEL_REQUESTED=; export SELINUX_LEVEL_REQUESTED

HISTCONTROL=ignoredups; export HISTCONTROL

SHLVL=1; export SHLVL

HOME=/root; export HOME

LOGNAME=root; export LOGNAME

CVS_RSH=ssh; export CVS_RSH

SSH_CONNECTION=192.168.137.1\ 56213\ 192.168.137.65\ 22; export SSH_CONNECTION

LESSOPEN=\|\|/usr/bin/lesspipe.sh\ %s; export LESSOPEN

G_BROKEN_FILENAMES=1; export G_BROKEN_FILENAMES

cd /root || {

     echo 'Execution directory inaccessible' >&2

     exit 1

}

${SHELL:-/bin/sh} << 'marcinDELIMITER1bfe0e60'

wall jobs1

wall jobs2

marcinDELIMITER1bfe0e60
[root@centos65 ~]# at  11:20  -f  atjobs.sh

job 7 at 2019-05-21 11:20

[root@centos65 ~]# at -l

4    2019-05-21 11:00 a root

7    2019-05-21 11:20 a root

2    2019-05-21 11:00 a root

6    2019-05-21 11:10 a root

5    2019-05-21 11:00 a root

3    2019-05-21 11:00 a root
[root@centos65 ~]# at -c   7

#!/bin/sh

# atrun uid=0 gid=0

# mail root 0

umask 22

HOSTNAME=centos65.jd.com; export HOSTNAME

SELINUX_ROLE_REQUESTED=; export SELINUX_ROLE_REQUESTED

SHELL=/bin/bash; export SHELL

HISTSIZE=1000; export HISTSIZE

SSH_CLIENT=192.168.137.1\ 56213\ 22; export SSH_CLIENT

SELINUX_USE_CURRENT_RANGE=; export SELINUX_USE_CURRENT_RANGE

SSH_TTY=/dev/pts/1; export SSH_TTY

USER=root; export USER

LS_COLORS=rs=0:di=01\;34:ln=01\;36:mh=00:pi=40\;33:so=01\;35:do=01\;35:bd=40\;33\;01:cd=40\;33\;01:or=40\;31\;01:mi=01\;05\;37\;41:su=37\;41:sg=30\;43:ca=30\;41:tw=30\;42:ow=34\;42:st=37\;44:ex=01\;32:\*.tar=01\;31:\*.tgz=01\;31:\*.arj=01\;31:\*.taz=01\;31:\*.lzh=01\;31:\*.lzma=01\;31:\*.tlz=01\;31:\*.txz=01\;31:\*.zip=01\;31:\*.z=01\;31:\*.Z=01\;31:\*.dz=01\;31:\*.gz=01\;31:\*.lz=01\;31:\*.xz=01\;31:\*.bz2=01\;31:\*.tbz=01\;31:\*.tbz2=01\;31:\*.bz=01\;31:\*.tz=01\;31:\*.deb=01\;31:\*.rpm=01\;31:\*.jar=01\;31:\*.rar=01\;31:\*.ace=01\;31:\*.zoo=01\;31:\*.cpio=01\;31:\*.7z=01\;31:\*.rz=01\;31:\*.jpg=01\;35:\*.jpeg=01\;35:\*.gif=01\;35:\*.bmp=01\;35:\*.pbm=01\;35:\*.pgm=01\;35:\*.ppm=01\;35:\*.tga=01\;35:\*.xbm=01\;35:\*.xpm=01\;35:\*.tif=01\;35:\*.tiff=01\;35:\*.png=01\;35:\*.svg=01\;35:\*.svgz=01\;35:\*.mng=01\;35:\*.pcx=01\;35:\*.mov=01\;35:\*.mpg=01\;35:\*.mpeg=01\;35:\*.m2v=01\;35:\*.mkv=01\;35:\*.ogm=01\;35:\*.mp4=01\;35:\*.m4v=01\;35:\*.mp4v=01\;35:\*.vob=01\;35:\*.qt=01\;35:\*.nuv=01\;35:\*.wmv=01\;35:\*.asf=01\;35:\*.rm=01\;35:\*.rmvb=01\;35:\*.flc=01\;35:\*.avi=01\;35:\*.fli=01\;35:\*.flv=01\;35:\*.gl=01\;35:\*.dl=01\;35:\*.xcf=01\;35:\*.xwd=01\;35:\*.yuv=01\;35:\*.cgm=01\;35:\*.emf=01\;35:\*.axv=01\;35:\*.anx=01\;35:\*.ogv=01\;35:\*.ogx=01\;35:\*.aac=01\;36:\*.au=01\;36:\*.flac=01\;36:\*.mid=01\;36:\*.midi=01\;36:\*.mka=01\;36:\*.mp3=01\;36:\*.mpc=01\;36:\*.ogg=01\;36:\*.ra=01\;36:\*.wav=01\;36:\*.axa=01\;36:\*.oga=01\;36:\*.spx=01\;36:\*.xspf=01\;36:; export LS_COLORS

MAIL=/var/spool/mail/root; export MAIL

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin; export PATH

PWD=/root; export PWD

LANG=en_US.UTF-8; export LANG

SELINUX_LEVEL_REQUESTED=; export SELINUX_LEVEL_REQUESTED

HISTCONTROL=ignoredups; export HISTCONTROL

SHLVL=1; export SHLVL

HOME=/root; export HOME

LOGNAME=root; export LOGNAME

CVS_RSH=ssh; export CVS_RSH

SSH_CONNECTION=192.168.137.1\ 56213\ 192.168.137.65\ 22; export SSH_CONNECTION

LESSOPEN=\|\|/usr/bin/lesspipe.sh\ %s; export LESSOPEN

G_BROKEN_FILENAMES=1; export G_BROKEN_FILENAMES

cd /root || {

     echo 'Execution directory inaccessible' >&2

     exit 1

}

${SHELL:-/bin/sh} << 'marcinDELIMITER7d9da0c8'

wall jobs1

wall jobs2

marcinDELIMITER7d9da0c8

（六）-m:当任务被完成之后，将给用户发送邮件，即使没有标准输出

[root@centos65 ~]# at  10:50  -m

at> true<EOT>

job 8 at 2019-05-21 10:50

[root@centos65 ~]# at -l

4    2019-05-21 11:00 a root

8    2019-05-21 10:50 a root

7    2019-05-21 11:20 a root

2    2019-05-21 11:00 a root

6    2019-05-21 11:10 a root

5    2019-05-21 11:00 a root

3    2019-05-21 11:00 a root

[root@centos65 ~]# date

Tue May 21 10:45:46 CST

按时发送了一封邮件

[root@centos65 ~]# mail

Heirloom Mail version 12.4 7/29/08.  Type ? for help.

"/var/spool/mail/root": 1 message 1 new

>N  1 root                  Tue May 21 10:50  13/453   "Output from your job        8"

& 1

Message  1:

From root@centos65.jd.com  Tue May 21 10:50:01 2019

Return-Path: <root@centos65.jd.com>

X-Original-To: root

Delivered-To: root@centos65.jd.com

Subject: Output from your job        8

To: root@centos65.jd.com

Date: Tue, 21 May 2019 10:50:00 +0800 (CST)

From: root@centos65.jd.com (root)

Status: R

五at时间格式示例

TIME:定义出什么时候进行 at 这项任务的时间
HH:MM [YYYY-mm-dd]
noon, midnight, teatime（4pm）
tomorrow
now+#{minutes,hours,days, OR weeks}

注意如果定义的计划任务时间超过了今天的时间，那么计划任务会在明天执行

比如现在是10点，定义的计划任务在9点那么最早就是明天的9点

[root@centos65 ~]# at  10:20

at> pwd

at> <EOT>

job 9 at 2019-05-22 10:20

[root@centos65 ~]# at -l

4    2019-05-21 11:00 a root

7    2019-05-21 11:20 a root

2    2019-05-21 11:00 a root

9    2019-05-22 10:20 a root

6    2019-05-21 11:10 a root

5    2019-05-21 11:00 a root

3    2019-05-21 11:00 a root

修改现在的时间

[root@centos65 ~]# at -l

4    2019-05-21 11:00 a root

7    2019-05-21 11:20 a root

2    2019-05-21 11:00 a root

9    2019-05-22 10:20 a root

6    2019-05-21 11:10 a root

5    2019-05-21 11:00 a root

3    2019-05-21 11:00 a root

[root@centos65 ~]# date   052210302019

Wed May 22 10:30:00 CST 2019

[root@centos65 ~]# date

Wed May 22 10:30:03 CST 2019

[root@centos65 ~]# at -l

4    2019-05-21 11:00 a root

7    2019-05-21 11:20 a root

2    2019-05-21 11:00 a root

9    2019-05-22 10:20 a root

6    2019-05-21 11:10 a root

5    2019-05-21 11:00 a root

3    2019-05-21 11:00 a root

硬件时间没变，重启之后先读取硬件时间

注意到了计划任务的时间，没有执行文件不会被删除

[root@centos65 ~]# clock

Tue 21 May 2019 10:58:15 AM CST  -0.563769 seconds

（一）从现在往后推多长时间

now+#{minutes,hours,days, OR weeks}

[root@centos72 ~]# at now+20minutes

at> pwd<EOT>

job 5 at Tue May 21 11:22:00 2019

[root@centos72 ~]# at -l

5    Tue May 21 11:22:00 2019 a root

[root@centos72 ~]# date

Tue May 21 11:03:11 CST

单位可以简写，但是不能不写

[root@centos72 ~]# at now+40min

at> ls<EOT>

job 6 at Tue May 21 11:44:00 2019

[root@centos72 ~]# at -l

5    Tue May 21 11:22:00 2019 a root

6    Tue May 21 11:44:00 2019 a root

（二）/etc/at.{allow,deny}控制用户是否能执行at任务

白名单：/etc/at.allow 默认不存在，只有该文件中的用户才能执行at命令
黑名单：/etc/at.deny 默认存在，拒绝该文件中用户执行at命令，而没有在at.deny 文件中的使用者则可执行
如果两个文件都不存在，只有 root 可以执行 at 命令

普通用户默认是可以执行计划任务的

[root@centos72 ~]# su - wang

Last login: Mon May 20 22:38:25 CST 2019 on pts/1

[wang@centos72 ~]$ at  11:10

at> wall  jobs1<EOT>

job 7 at Tue May 21 11:10:00 2019

[wang@centos72 ~]$ at -l

7    Tue May 21 11:10:00 2019 a wang

[wang@centos72 ~]$ date

Tue May 21 11:08:49 CST 2019

[wang@centos72 ~]$ pwd

/home/wang

[wang@centos72 ~]$

Broadcast message from wang@centos72.huawei.com (Tue May 21 11:10:00 2019):

jobs1

^C

让普通用户不能执行计划任务

[wang@centos72 ~]$ exit

logout

[root@centos72 ~]# ll  /etc/at.deny

-rw-r--r--. 1 root root 1 Oct 31  2018 /etc/at.deny

[root@centos72 ~]# cat  /etc/at.deny 

[root@centos72 ~]# echo  wang  >  /etc/at.deny

[root@centos72 ~]# cat  /etc/at.deny

wang

[root@centos72 ~]# su - wang

Last login: Tue May 21 11:08:19 CST 2019 on pts/0

[wang@centos72 ~]$ at  -l

You do not have permission to use at.

[wang@centos72 ~]$ at  11:20

You do not have permission to use at.

[wang@centos72 ~]$ pwd

/home/wang

[wang@centos72 ~]$

白名单：/etc/at.allow 默认不存在，只有该文件中的用户才能执行at命令

注意如果黑名单白名单都有的用户那么白名单优先生效，但是不在白名单里面的用户就会被拒绝

如果没有白名单文件，那么在黑名单之外的其他用户会被允许

[root@centos72 ~]# cat /etc/at.allow

cat: /etc/at.allow: No such file or directory

[root@centos72 ~]# echo wang  > /etc/at.allow

[root@centos72 ~]# cat /etc/at.allow

wang

[root@centos72 ~]# ll /etc/at.allow

-rw-r--r--. 1 root root 5 May 21 11:15 /etc/at.allow

[root@centos72 ~]# su - wang

Last login: Tue May 21 11:12:27 CST 2019 on pts/0

[wang@centos72 ~]$ at  -l

[wang@centos72 ~]$ at  11:20

at> ls<EOT>

job 8 at Tue May 21 11:20:00 2019

[wang@centos72 ~]$ at  -l

8    Tue May 21 11:20:00 2019 a wang

[wang@centos72 ~]$

目前只有wang才可以创建计划任务

[root@centos72 ~]# cat /etc/at.allow

wang

[root@centos72 ~]# cat /etc/at.deny

wang

[root@centos72 ~]# cat /etc/passwd

root:x:0:0:root:/root:/bin/bash

bin:x:1:1:bin:/bin:/sbin/nologin

daemon:x:2:2:daemon:/sbin:/sbin/nologin

adm:x:3:4:adm:/var/adm:/sbin/nologin

lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin

sync:x:5:0:sync:/sbin:/bin/sync

shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown

halt:x:7:0:halt:/sbin:/sbin/halt

mail:x:8:12:mail:/var/spool/mail:/sbin/nologin

operator:x:11:0:operator:/root:/sbin/nologin

games:x:12:100:games:/usr/games:/sbin/nologin

ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin

nobody:x:99:99:Nobody:/:/sbin/nologin

systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin

dbus:x:81:81:System message bus:/:/sbin/nologin

polkitd:x:999:998:User for polkitd:/:/sbin/nologin

sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin

postfix:x:89:89::/var/spool/postfix:/sbin/nologin

wang:x:1000:1000:wang:/home/wang:/bin/bash

apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

rooter:x:1001:1001::/home/rooter:/bin/bash

123:x:1002:1002::/home/123:/bin/bash

[root@centos72 ~]# su - rooter

[rooter@centos72 ~]$ pwd

/home/rooter

[rooter@centos72 ~]$ at -l

You do not have permission to use at.

[rooter@centos72 ~]$ at  11:20

You do not have permission to use at.

[rooter@centos72 ~]$ exit

logout

如果两个文件都不存在，只有 root 可以执行 at 命令

[root@centos72 ~]# rm -f  /etc/at.*

[root@centos72 ~]# cat /etc/at.deny

cat: /etc/at.deny: No such file or directory

[root@centos72 ~]# cat /etc/at.allow

cat: /etc/at.allow: No such file or directory

[root@centos72 ~]# su - wang

Last login: Tue May 21 11:15:48 CST 2019 on pts/0

[wang@centos72 ~]$ at -l

You do not have permission to use at.

at具有特殊权限

[root@centos72 ~]# which at

/usr/bin/at

[root@centos72 ~]# ll  /usr/bin/at

-rwsr-xr-x. 1 root root 53048 Oct 31  2018 /usr/bin/at

无法控制管理员

[root@centos72 ~]# echo  root  >  /etc/at.deny

[root@centos72 ~]# cat /etc/at.deny

root

[root@centos72 ~]# at -l

6    Tue May 21 11:44:00 2019 a root

[root@centos72 ~]# at  11:30

at> pwd

at> <EOT>

job 9 at Tue May 21 11:30:00 2019

[root@centos72 ~]# at -l

6    Tue May 21 11:44:00 2019 a root

9    Tue May 21 11:30:00 2019 a root

at使用的不多

一次性删除多个计划任务，直接删除文件即可

[root@centos72 ~]# at -l

6    Tue May 21 11:44:00 2019 a root

9    Tue May 21 11:30:00 2019 a root

[root@centos72 ~]# ls /var/spool/at/

a00006018c5300  spool

You have new mail in /var/spool/mail/root

[root@centos72 ~]# rm -f  /var/spool/at/a00006018c5300

[root@centos72 ~]# ls /var/spool/at/

spool

[root@centos72 ~]# at -l

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