20-Openwrt crond crontab

crond and corntab All are busybox Next tool ,crond It's a background process , Read the parameters in the configuration file every minute , Perform the corresponding action .crontab Is a command line provided , You can add, delete, modify and check the configuration file . This timing function is very convenient for ordinary functions , Like every night 12 Click restart router .

1、openwrt Start the crond process

crond The startup parameters of are as follows ：

Usually set -c Specify the file directory ,-l The log level

# crond -h
crond: invalid option -- h
BusyBox v1.22.1 (2022-03-14 17:26:20 CST) multi-call binary.

Usage: crond -fbS -l N -L LOGFILE -c DIR

        -f      Foreground
        -b      Background (default)
        -S      Log to syslog (default)
        -l      Set log level. 0 is the most verbose, default 8
        -L      Log to file
        -c      Working dir

openwrt In or out /etc/init.d/ There is cron Start the program , as follows

# cat /etc/init.d/cron
#!/bin/sh /etc/rc.common
# Copyright (C) 2006-2011 OpenWrt.org

START=50

USE_PROCD=1
PROG=/usr/sbin/crond

validate_cron_section() {
        uci_validate_section system system "${1}" \
                'cronloglevel:uinteger'
}

start_service () {
        [ -z "$(ls /etc/crontabs/)" ] && return 1

        loglevel=$(uci_get "[email protected][0].cronloglevel")

        [ -z "${loglevel}" ] || {
                /sbin/validate_data uinteger "${loglevel}"
                [ "$?" -eq 0 ] || {
                        echo "validation failed"
                        return 1
                }
        }

        mkdir -p /var/spool/cron
        ln -s /etc/crontabs /var/spool/cron/ 2>/dev/null

        procd_open_instance
        procd_set_param command "$PROG" -f -c /etc/crontabs -l ${loglevel:-5}
        procd_close_instance
}

service_triggers()
{
        procd_add_validation validate_cron_section
}

The startup process is as follows ：

# ps | grep crond
27141 root      1528 S    /usr/sbin/crond -f -c /etc/crontabs -l 5

stay system Modules can be added crond start-up log Level of , The default is 5

# cat /etc/config/system

config system
        option zonename 'Asia/Shanghai'
        option timezone 'CST-8'
        option cronloglevel '4'

2、crontab Command to use

List the current default scheduled task list ：

crontab -l

Delete the current default scheduled task list ：

crontab -r

Modify the current default scheduled task list , It's really just using vi open /etc/crontabs/root File for editing

crontab -e

above crontab Command is actually a chicken rib , Direct use cat/vi View modification /etc/crontabs/root Just a file .

3、 Create a scheduled task

Format of planning task list ：

[minute] [hour] [day of month] [month] [day of week] [program to be run]

The value range of each parameter is :

minute(0-59)

hour(0-23)

day of month(1-31)

month(1-12)

day of week(0-7,0 or 7 is Sun)

The value in each parameter can have 4 A kind of separator :

*  Express arbitrarily 

–  Scope of representation 

,  Indicates to enumerate multiple values 

/  Said every 

for example :

Every night from Monday to Friday 23:30 Restart the system

30 23 * * 1-5 reboot

Every other day 10 Minute execution run.sh Script

*/10 * * * * date

Every day 14 spot -15 spot , And every day 20 Point to -21 spot , Every 15 Once per minute run.sh Script

echo "*/15 14,20 * * * date" >> /etc/crontabs/root

Task added to /etc/crontabs/root After inside , It won't take effect until the next minute , because crond The process executes every other minute , If you want to take effect immediately , Just restart crond Conduct /etc/init.d/crond restart

Linux crontab command ：https://www.runoob.com/linux/linux-comm-crontab.html