[[email?protected] ~]# 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!

[[email?protected] ~]# rpm  -q at
at-3.1.13-23.el7.x86_64 [[email?protected] ~]# 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.

[[email?protected] ~]#  rpm -q  at
at-3.1.10-48.el6.x86_64 [[email?protected] ~]# 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.

[[email?protected] ~]# 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

[[email?protected] ~]#  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

[[email?protected] ~]# systemctl is-enabled  atd
enabled
[[email?protected] ~]# systemctl is-enabled atd.service enabled

[[email?protected] ~]# chkconfig  --list  atd
atd                0:off 1:off 2:off 3:on 4:on 5:on 6:off [[email?protected] ~]# runlevel N 3

[[email?protected] ~]# systemctl status  atd.service 
● atd.service - Job spooling tools Loaded: loaded (/usr/lib/systemd/system/atd.service; enabled; vendor preset: enabled) Active: inactive (dead) [[email?protected] ~]# systemctl start atd.service [[email?protected] ~]# 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...

[[email?protected] ~]# 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 2710

[[email?protected] ~]# at  10:00 at> wall 10:00 clock at> <EOT> job 1 at Tue May 21 10:00:00 2019 [[email?protected] ~]# at -l 1 Tue May 21 10:00:00 2019 = root [[email?protected] ~]# Broadcast message from [email?protected] (Tue May 21 10:00:01 2019): 10:00 clock

[[email?protected] ~]# at  10:10 at> wall 10:10 clock at> <EOT> job 2 at Tue May 21 10:10:00 2019 [[email?protected] ~]# at -l 2 Tue May 21 10:10:00 2019 a root [[email?protected] ~]# 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

[[email?protected] ~]# 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=