09/05做业

Linux任务计划

任务计划：

                   在将来时间点一次性执行某任务：at, batch

                   周期性执行某任务: crontab

at：

 

                   承载将来时间运行的某做业：

 

                   支持使用做业队列：

                            默认为a队列；

                   Ctrl+d保存任务

                   at [option]... TIME

                   TIME:

                            (1) 绝对时间

                                     HH:MM,

                                     MMDD[CC]YY,MM/DD/[CC]YY, DD.MM.[CC]YY or [CC]YY-MM-DD

                                     tomorrow

                            (2) 相对时间

                                     now+#UNIT

                                               minute,hour, day, week

                            (3) 模糊时间

                                     Midnight 午夜

                                     Noon下午

                                     Teatime 下午茶时间

                   经常使用选项：

                            -q QUEUE： at做业队列；

                            -f/PATH/FROM/SOMEFILE：从指定的文件中读取要运行的做业；

                            -l: 查看做业队列中的等运行做业列表；至关于使用atq命令；

                            -c AT_JOB_NUM: 查看待运行做业的内容；

                            -d: 删除指定做业；至关于atrm

batch:

                   由系统自行选择在资源较为空闲时运行指定的任务；

crontab：周期性任务计划

                   守护进程：crond

 

                   周期性任务有两类：

                            (1) 系统cron任务；没有默认运行用户身份，因此须要额外指定运行者；

                                     /etc/crontab

                                     vim命令

                                               #Example of job definition:

                                               #.---------------- minute (0 - 59)

                                               #|  .------------- hour (0 - 23)

                                               #|  | .---------- day of month (1 - 31)

                                               #|  | |  .------- month (1 - 12) ORjan,feb,mar,apr ...

                                               #|  | |  |  .---- day of week (0 - 6) (Sunday=0 or 7) ORsun,mon,tue,wed,thu,fri,sat

                                               #|  | |  |  |

                                               #*  * *  *  * user-name command to be executed    

 

                                               7个字段：

                                                        前5个字段：时间点

                                                        user-name:以user-name运行

                                                        commandto be executed: 要运行任务                           

 

                            (2) 用户cron任务：由某个用户所提交，默认就以提交者的身份运行，因此无需额外指定运行者；

                                     /var/spool/cron/USERNAME

 

                                     vim命令；不建议

                                     crontab命令：建议

 

                                               #Example of job definition:

                                               #.---------------- minute (0 - 59)

                                               #|  .------------- hour (0 - 23)

                                               #|  | .---------- day of month (1 - 31)

                                               #|  | |  .------- month (1 - 12) ORjan,feb,mar,apr ...

                                               #|  | |  |  .---- day of week (0 - 6) (Sunday=0 or 7) ORsun,mon,tue,wed,thu,fri,sat

                                               #|  | |  |  |

                                               #*  * *  *  * command to be executed      

                                               5个时间点：

                                                        分钟：有效取值范围0-59；

                                                        小时：0-23

                                                        日：1-31

                                                        月：1-12

                                                        周几：0-7

                                                        注意：几月几号与周几，不建议同时使用；

                                                        时间表示法：

                                                                 *:对应时间点有效取值范围内的每一个时间点；

                                                                 -:一个特定连续时间范围, 3-7

                                                                 ,：一个离散的时间点, 3,5,7

                                                                 /#：有效时间范围内的每多少时间；用于指定频率；

                                                                           1-30/4,*/4

 

                                                        5*/3 * * * /bin/echo "howdy"

 

                                                        57 * * 1-5 /bin/echo "howdy"

 

                                               crontab命令：

                                                        crontab[-u user] [-l | -r | -e]

                                                                 -uuser: 不是管理本身的cron任务，而是指定的目标用户的cron任务；仅root拥有管理其它用户的cron任务的权限；默认管理本身的；

 

                                                                 -l:list，列出任务；

                                                                 -r: remove,移除全部任务；

                                                                 -e:edit，编辑，打开一当前shell会话的默认编辑器来编辑cron任务表；

练习

每周一到周六的凌晨3点20分，运行cp命令对/etc/目录进行归档另存，存储位置为/backups/etc-YYYY-MM-DD

20 3 * * 1-6/bin/cp  /backups/etc-‘date+%d’

每周日凌晨2点30分，运行cp命令对/etc/fstab文件进行备份，存储位置为/backup/fstab-YYYY-MM-DD-hh-mm-ss

30 2 * */bin/cp  /etc/fstab-‘date+%Y-%m-%d-%H-%M-%S’