linux定时任务

发表于

工具和命令

  • ubuntu OS
  • cron, crontab

一个简单的定时任务

1 开启日志记录

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sudo vim /etc/rsyslog.d/50-default.conf
# remove the '#' before cron.*
# save 50-default.conf
sudo  service rsyslog  restart

2 日志文件测试

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crontab -e

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# this task will be done once per minute
* * * * * echo "@@@@@@@ test for crontab" >> /tmp/test.txt 2>&1

3 查看日志文件

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# we openned the cron log
cat /var/log/cron.log
# we log the echo to this file
cat /tmp/test.txt

4 删除这条定时任务

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crontab -e
# delete the command line

一个复杂的定时任务 auto renew https certs

1 开启日志记录

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sudo vim /etc/rsyslog.d/50-default.conf
# remove the '#' before cron.*
# save 50-default.conf
sudo  service rsyslog  restart

2 准备shell 脚本

尽量使用绝对路径, 不知道命令的路径可以使用which 查看, 比如： which node, which pm2

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#/home/ubuntu/shell/renew.sh
echo "===================== stop https server ..."
/home/ubuntu/.nvm/versions/node/v8.9.1/bin/pm2 delete all
echo "@@@@@@@ stop nginx ..."
sudo service nginx stop
echo "renew ..."

# Be careful with this line, you can only generate 7 certs per week using letsencript
# You can comment this line or remove '--force-renewal' when you test
sudo certbot renew --force-renewal
echo "@@@@@@@ restart nginx ..."
sudo service nginx restart
echo "@@@@@@@ start https server ..."
NODE_ENV=cnProduction /home/ubuntu/.nvm/versions/node/v8.9.1/bin/pm2 start /home/ubuntu/MODELO_backend/server.js
echo "===================== renew finished"

3 添加定时任务

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crontab -e

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# this task will be done at 1st 01:01 in month 2,4,6,8,10,12
1 1 1 2,4,6,8,10,12 * /bin/sh /home/ubuntu/shell/renew.sh >> /tmp/test.txt 2>&1

4 查看日志

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cat /var/log/cron.log
cat /tmp/test.txt

常见错误

/usr/bin/env:node No such file or directory

非常大可能是 环境变量不对
我遇到的是使用pm2 时node路径不对，找不到node

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ln -s /usr/bin/nodejs /usr/bin/node
# ln -s _your_node_path /usr/bin/node
# ln -s /usr/local/bin/nodejs /usr/bin/node

ref https://github.com/nodejs/node-v0.x-archive/issues/3911

No MTA installed, discarding output

没有邮件服务器，放弃日志
通常在每个命令末尾加上>> /tmp/test.txt 2>&1将日志输出到文件

XXXXXXX not found

such as pm2: not found
something like No such file or directory
we can use the absolute path

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# wrong
pm2 start 

# right
/home/ubuntu/.nvm/versions/node/v8.9.1/bin/pm2 start