09/05做業

Linux任務計劃

任務計劃：

                   在將來時間點一次性執行某任務：at, batch

                   週期性執行某任務: crontab

at：

 

                   承載將來時間運行的某做業：

 

                   支持使用做業隊列：

                            默認爲a隊列；

                   Ctrl+d保存任務

                   at [option]... TIME

                   TIME:

                            (1) 絕對時間

                                     HH:MM,

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

                                     tomorrow

                            (2) 相對時間

                                     now+#UNIT

                                               minute,hour, day, week

                            (3) 模糊時間

                                     Midnight 午夜

                                     Noon下午

                                     Teatime 下午茶時間

                   經常使用選項：

                            -q QUEUE： at做業隊列；

                            -f/PATH/FROM/SOMEFILE：從指定的文件中讀取要運行的做業；

                            -l: 查看做業隊列中的等運行做業列表；至關於使用atq命令；

                            -c AT_JOB_NUM: 查看待運行做業的內容；

                            -d: 刪除指定做業；至關於atrm

batch:

                   由系統自行選擇在資源較爲空閒時運行指定的任務；

crontab：週期性任務計劃

                   守護進程：crond

 

                   週期性任務有兩類：

                            (1) 系統cron任務；沒有默認運行用戶身份，因此須要額外指定運行者；

                                     /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個字段：

                                                        前5個字段：時間點

                                                        user-name:以user-name運行

                                                        commandto be executed: 要運行任務                           

 

                            (2) 用戶cron任務：由某個用戶所提交，默認就以提交者的身份運行，因此無需額外指定運行者；

                                     /var/spool/cron/USERNAME

 

                                     vim命令；不建議

                                     crontab命令：建議

 

                                               #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個時間點：

                                                        分鐘：有效取值範圍0-59；

                                                        小時：0-23

                                                        日：1-31

                                                        月：1-12

                                                        周幾：0-7

                                                        注意：幾月幾號與周幾，不建議同時使用；

                                                        時間表示法：

                                                                 *:對應時間點有效取值範圍內的每一個時間點；

                                                                 -:一個特定連續時間範圍, 3-7

                                                                 ,：一個離散的時間點, 3,5,7

                                                                 /#：有效時間範圍內的每多少時間；用於指定頻率；

                                                                           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任務，而是指定的目標用戶的cron任務；僅root擁有管理其它用戶的cron任務的權限；默認管理本身的；

 

                                                                 -l:list，列出任務；

                                                                 -r: remove,移除全部任務；

                                                                 -e:edit，編輯，打開一當前shell會話的默認編輯器來編輯cron任務表；

練習

每週一到週六的凌晨3點20分，運行cp命令對/etc/目錄進行歸檔另存，存儲位置爲/backups/etc-YYYY-MM-DD

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

每週日凌晨2點30分，運行cp命令對/etc/fstab文件進行備份，存儲位置爲/backup/fstab-YYYY-MM-DD-hh-mm-ss

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