crontab usage

一般若要某 user 定時執行某件事情, 就以那個 user 的帳號執行 crontab -e 就可以建立定時要執行的事情. 注意: 不要直接 edit crontab  檔案, 而是執行 crontab -e.

For Ubuntu
Method A: crontab -e
  1. as "user" login
  2. crontab -e
  3. # m h dom mon dow command
      0,20,40 * * * * /home/fae/git_repo/git_pull.sh >> /home/fae//Logs/git/git-"$(date +\%F_\%T)".log 2>&1

Method B: edit crontab file. This method doesn't work for CentOS.

  1. as root

  2. vim /etc/crontab

  3. as user "fae" to execute command

      # m h dom mon dow command

      0,20,40 * * * *   fae  /home/fae/git_repo/git_pull.sh >> /home/fae//Logs/git/git-"$(date +\%F_\%T)".log 2>&1
  4. restart cron service
      sudo service cron reload
      or
      /etc/init.d/cron reload

Method C: sudo crontab -e
  1. as "user" login
  2. sudo crontab -e
  3. # m h dom mon dow command

      0,20,40 * * * * /home/fae/git_repo/git_pull.sh >> /home/fae/Logs/git/git-"$(date +\%F_\%T)".log 2>&1
      10 3 * * 1-5 /home/fae/Tools/trim/trim_ssd.sh >> /home/fae/Logs/trim/trim-"$(date +\%F_\%T)".log 2>&1

觀察 crontab 執行結果
1.  sudo cat /var/log/syslog | grep CRON
2.  cat log.txt

Solved CRON no MTA install
  message ---- "CRON[8380]: (CRON) info (No MTA installed, discarding output)"

sudo apt-get install postfix

Example: git_pull.sh

#! /bin/bash

echo -e " "
echo -e "###############################################################"
echo -e "# SYNC start" `date +%Y_%m%d_%H:%M:%S`
echo -e " ---- git pull jmt_driver ---- "
cd /home/fae/git_repo/jmt_driver
git reset --hard HEAD
git pull

echo -e " ---- git pull jmt_docs ---- "
cd ../jmt_docs
git reset --hard HEAD
git pull

Example: crontab -e

0,20,40 * * * *      /home/fae/git_repo/git_pull.sh >> /home/fae/pull_log/git_pull_log.txt

For CentOS
Method A: crontab -e
  1. as "user" login
  2. crontab -e
  3. # m h dom mon dow command
      0,20,40 * * * * /home/fae/git_repo/git_pull.sh >> /home/fae//Logs/git/git-"$(date +\%F_\%T)".log 2>&1

Method B: edit crontab file. This method doesn't work for CentOS.

  1. as root

  2. vim /etc/crontab

  3. as user "fae" to execute command

      # m h dom mon dow command

      0,20,40 * * * *   fae  /home/fae/git_repo/git_pull.sh >> /home/fae//Logs/git/git-"$(date +\%F_\%T)".log 2>&1
  4. restart cron service
      sudo service cron reload
      or
      /etc/init.d/cron reload

Method C: sudo crontab -e
  1. as "user" login
  2. sudo crontab -e
  3. # m h dom mon dow command

      0,20,40 * * * * /home/fae/git_repo/git_pull.sh >> /home/fae/Logs/git/git-"$(date +\%F_\%T)".log 2>&1
      10 3 * * 1-5 /home/fae/Tools/trim/trim_ssd.sh >> /home/fae/Logs/trim/trim-"$(date +\%F_\%T)".log 2>&1


Crontab tack effect
  For Ubuntu

sudo service cron reload

or

/etc/init.d/cron reload

  For CentOS

sudo systemctl start crond.service

觀察 crontab 執行結果
1.  sudo cat /var/log/cron | grep -i corn
2.  cat log.txt

Example: git_pull.sh

#! /bin/bash

echo -e " "
echo -e "###############################################################"
echo -e "# SYNC start" `date +%Y_%m%d_%H:%M:%S`
echo -e " ---- git pull jmt_driver ---- "
cd /home/fae/git_repo/jmt_driver
git reset --hard HEAD
git pull

echo -e " ---- git pull jmt_docs ---- "
cd ../jmt_docs
git reset --hard HEAD
git pull

Example: trim_ssd.sh

#! /bin/bash

sudo fstrim  -v /ssd1
sudo fstrim  -v /ssd2

Example: crontab -e

0,20,40 * * * *      /home/fae/git_repo/git_pull.sh >> /home/fae/pull_log/git_pull_log.txt