Linux crontab and using salt for management

First, Introduction:

I have recently inadvertently seen salt with a cron module, here today to introduce the Linux crontab and the management of crontab through the salt cron.

Second, the introduction of Linux crontab:

The crontab is used to set instructions that are executed periodically. The command reads the instruction from the standard input device and stores it in a "crontab" file for later reading and execution. Crontab stored instructions are activated by daemons, Crond often run in the background, and every minute checks whether a scheduled job needs to be executed.

2.1. Startup and shutdown of Crond:

#View the status of Crond[[Email protected] ~]#Service Crond Status#Close Crond[[Email protected] ~]#Service Crond Stop#Start Crond[[Email protected] ~]#Service Crond Start#Restart Crond[[Email protected] ~]#Service Crond Restart#Reload Crond[[Email protected] ~]#Service Crond Reload

2.2. All configuration Files

Crontab exists in the/etc directory cron.hourly,cron.daily,cron.weekly,cron.monthly,cron.d five directories and crontab,cron.deny two files.

Cron.daily is a job that executes once a day;

Cron.weekly is a job that executes once a week;

Cron.monthly is a job that executes once a month;

Cron.hourly is the job that executes once per hour;

CRON.D is a task that the system automatically needs to do on a regular basis, but it is not performed by the hour, by day, by week, by month.

The contents of/etc/crontab are as follows:

[[Email protected] ~]#Cat/etc/crontabshell=/bin/Bashpath=/sbin:/bin:/usr/sbin:/usr/Binmailto=Root#For details see Mans 4 Crontabs#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

A/etc/cron.deny file is a feature that controls which users are not allowed to use crontab.

2.3. User Configuration file:

Each user has their own cron configuration file, through Crontab-e can be edited, in general, we finished editing the user's cron configuration file after the exit, the system will automatically be stored in the/var/spool/cron/directory, the file is named after the user name.

The cron service for Linux is to read all the contents of/var/spool/cron/,/etc/crontab,/etc/cron.d every other minute.

2.4. Cron Command format:

| -r | - E} -u: Specify a user-e: Perform a text editor to set the user (current user or specified user) time table, the default text editor is vi.-r: Delete User Time table.-L: Lists the user Time table.

2.5. Cron file Format:

* * * * * *  command time    Moon Week the  1th column represents minutes 1~59, per minute with * or */1 for the2nd column represents the hour 1~( 0 = 0 points) The 3rd column represents the date 1~to the 4th column represents the month 1~ 5th Column identification number week 0~6(0 for Sunday) 6th Column command to run

2.6. Special Users:

[[email protected] cron] # crontab-l # Lines below here is managed by Salt,does not edit @reboot/root/cgroup_mkdir.sh

@reboot means running after booting and running only once, with the same effect as in/etc/rc.local.

In addition, there are:

string Meaning------           -------@reboot Run once, at startup @yearly Run once a,"0 0 1 1 *". @annually (same as @yearly) @monthly Run once a month,"0 0 1 * *". @weekly Run Once a week,"0 0 * 0". @daily Run Once a day,"0 0 * * *". @midnight (same as @daily) @hourly Run Once an hour,"0 * * * *".

2.7. Run once every 10 seconds:

Third, through salt to manage crontab:

3.1.

Not to be continued ...

Linux crontab and using salt for management