Linux Task Scheduler

Linux Task Scheduler

Note: The results of each execution of a Linux task plan, including errors, will be sent to the administrator in message format, so you must install the Mail service to view the results of the task execution

1. 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]

To see if the Mail Service started: Netstat-tlnup | grep 25

2, at command: Automatically perform some pre-set command actions at the specified date and point of time, belonging to a one-off scheduled task

To host a job that runs in the future time:

Support for using job queues:

The default is a queue;

Save Task: Ctrl+d

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

Service Script Name:/ETC/INIT.D/ATD

syntax format: at {hours: minutes} {year-month-day}

ATQ: User queries the currently set at Task List

ATRM: Delete the at task with the specified task number

Example: Application of RELATED commands

[[email protected] ~]# date2015  09 month  05 day   Saturday  18:39:54 CST[[email  Protected] ~]# at 18:41 2015-09-05at> touch /aaat> <eot>job  2 at 2015-09-05 18:41[[email protected] ~]# atq2        2015-09-05 18:41 a root[[email protected] ~]# stat /aa   File:  "/AA"   Size: 0                Blocks: 0           io block: 4096    Plain Empty file device: fd00h/64768d    inode: 14           Links: 1Access:  (0644/-rw-r--r--)    Uid:  (    0/    root)    Gid:  (     0/ &Nbsp;  root) access: 2015-09-05 18:41:01.325106256 +0800modify: 2015-09-05  18:41:01.325106256 +0800change: 2015-09-05 18:41:01.325106256 +0800[[email protected]  ~]# at 23:59at> touch /bbat> <EOT>job 3 at  2015-09-05 23:59[[email protected] ~]# atq3        2015-09-05 23:59 a root[[email protected] ~]# atrm 3[[email protected]  ~]# atq

Batch

The system chooses to run the specified task when the resource is more idle;

3, Crontab: According to the pre-set time period (minutes, hours, days ...) Repeatedly executes user-specified command actions, which are periodic scheduled tasks

Service Script Name:/etc/init.d/crond

The global configuration file is located at:/etc/crontab

There are two types of recurring tasks:

(1) System cron task; There is no default running user identity, so you need to specify the additional runner;

/etc/crontab

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

(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

# * * * * * command to be executed

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;

Each field Description:

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Special representations of time values:

*: Indicates any time within the range

,: Multiple discontinuous points of time representing the interval

-: Represents a continuous range of time

/: Specify the time frequency of the interval

Example: 017**1-5 Monday to Friday daily 17:003088*1,3,5 every Monday, three, five 8:30 08-18/2***8 points to 18 points each two hours 0**/3** every three days

system default settings and scripts, located in directory /etc/cron.*/

User-defined This is, located in the file /var/spool/cron/user name

Manage Cron Scheduled Tasks:

Edit Scheduled Task:crontab–e {-u user name}

View Scheduled Tasks:crontab–l {-u user name}

Delete Scheduled Task:crontab–r {-u user name}

Attention:

(1) If you do not want to receive notification messages for task execution results:

COMMAND >/dev/null

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;

such as:/bin/cp-rfp/etc//backups/etc-' Date +\%y\%m\%d '

(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

such as:/root/bin/a.sh

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;

Answer: 3 * * 1-6/bin/cp-rfp/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

Answer: 2 * * 7/bin/cp-rfp/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;

Answer: 0 0 * * */bin/egrep--color=auto ' ^s|^m '/proc/meminfo >>/statistics/meminfo.txt && Echo =============== ============ >>/statistics/meminfo.txt

This article comes from "doing what you want to do!" "Blog, be sure to keep this provenance http://807257775.blog.51cto.com/2448194/1691610

Linux Task Scheduler