Task Plan Categories:
Perform a task at a time in the future: at, Batch
To perform a task periodically: crontab
e-Mail Service:
Smtp:simple Mail Transmission protocol
/var/spool/mail/username
Pop3:post Office Protocol
Imap4:internet Mail Access Protocol
Mail command:
Mail: Enter the interactive email interface;
Mail-s ' SUBJECT ' [email protected]
Mail-s ' SUBJECT ' [email protected] </path/from/somefile
COMMAND | Mail-s ' SUBJECT ' [email protected]
AT command:
To host a job that runs in the future time:
Support for using job queue: default to a queue;
Ctrl+d Submitting Jobs
Format: at [option] ... Time
Time:
(1) Absolute time
HH:MM,
Mmdd[cc]yy, Mm/dd/[cc]yy, dd.mm.[cc]yy or [cc]yy-mm-dd
Tomorrow
(2) Relative time
now+ #UNIT
Minute, hour, day, week
(3) Blur time
Midnight
Noon
Teatime
Common options:
-Q queue:at Job queue;
-f/path/from/somefile: Reads the job to be run from the specified file;
-L: View a list of such running jobs in the job queue; equivalent to using the ATQ command;
-C At_job_num: Look at the contents of the running job;
-D: Delete the specified job; equivalent to ATRM
5.batch: using at for command execution, the system chooses to run the specified task when the resource is more idle;
6. Crontab Recurring Mission Plan
6.1 Daemon:crond, monitoring whether a task arrives at a point in time
6.2 Recurring tasks are available in two categories:
(1) System cron task; There is no default running user identity, so you need to specify the additional runner;/etc/crontab
Basic format:
# Example of Job definition:
#.----------------Minute (0-59)
# | .-------------Hour (0-23)
# | | .----------Day of Month (1-31)
# | | | .-------month (1-12) OR jan,feb,mar,apr ...
# | | | | .----Day of Week (0-6) (sunday=0 or 7) or Sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * * user-name command to be executed
7 fields:
Top 5 fields: Point in time
User-name: Run the task as a user
command to being executed: to run a task
(2) User Cron Task: Submitted by a user, the default is to run as the submitter, so there is no need to specify the additional runner;/var/spool/cron/username
Format:
# Example of Job definition:
#.----------------Minute (0-59)
# | .-------------Hour (0-23)
# | | .----------Day of Month (1-31)
# | | | .-------month (1-12) OR jan,feb,mar,apr ...
# | | | | .----Day of Week (0-6) (sunday=0 or 7) or Sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * command to be executed
5 Time points:
Minutes: valid value range 0-59;
Hours: 0-23
Day: 1-31
Month: 1-12
Weeks: 0-7
Note: The date of the month and the number of weeks, not recommended to use at the same time;
6.3 Time notation:
*: Each time point in the valid value range of the time point;
-: A specific continuous time range, 3-7
,: A discrete point in time, 3,5,7
/#: The amount of time in a valid time frame, for specifying the frequency;
6.4 crontab Command:
crontab [-u user] [-l |-r |-e]
-u User: Not to manage your own cron task, but to specify the target user's cron task; Root has the ability to manage other users ' cron tasks; default management of their own;
-l:list, list the tasks;
-r:remove to remove all tasks;
-e:edit, edit, open a default editor for the current shell session to edit the cron task table;
6.5 Complementary Tools : Anacron:
6.6 Note:
(1) If you do not want to receive notification messages for task execution results:
normal results not received : COMMAND >/dev/null
all results are not received : COMMAND &>/dev/null
(2) for crontab file,% has a special function, if the command will appear in the%, remember to escape, or use single quotation marks to its reference;
(3) Crontab's path variable is not exactly the same as the user's variable, so it is recommended that the task in cron use an absolute path
Practice:
1, every Monday to Saturday 3:20 A.M., run the CP command to archive the/etc/directory, storage location is/BACKUPS/ETC-YYYY-MM-DD;
[email protected] ~]# which Cpalias cp= ' cp-i '/bin/cp[[email protected] ~]# Crontab-eno crontab for root-using an empt Y onecrontab:installing new Crontab[[email protected] ~]# CRONTAB-L20 3 * * 1-6/bin/cp/etc//backups/etc-' Date +%Y-%m- %d '/
2, every Sunday 2:30 A.M., run the CP command to backup the/etc/fstab file, the storage location is/BACKUP/FSTAB-YYYY-MM-DD-HH-MM-SS
2 * * 1-6/bin/cp/etc/fstab/backups/fstab-' date +%y-%m-%d-%h-%m-%s '/
3, every night 12 o'clock, get all the lines in the/proc/meminfo file starting with S or M, appended to the/statistics/meminfo.txt file, and the daily message before, to add a similar =============== separator line;
0 0 * * */bin/echo ========== >>/statistics/meminfo.txt &&/bin/egrep ' ^s|^m '/proc/meminfo >>/stati Stics/meminfo.txt
Task scheduling--9.5 jobs on Linux