how to track issue
sudo /var/log/syslog | grep cron
capture the output
1 2 * * * /home/hyy/Start.py >/tmp/output.log 2>&1
check cron is running
ps -ef | grep cron | grep -v grep
check the path is correct
- crontab is running in with cwd == $HOME, if you using python os.getcwd() in different folder structure, make sure you cd to the correct place or else it will affect your code by output “can not find module” stuff.
- in short, use absolute path in your command or add
source ~/.zshrc before your crontab script, so it can find the environment variable
last command in crontab should have a blank line
- this is tricky, if you didn’t notice it.
be careful the dot thing
- Debian Linux and its derivative (Ubuntu, Mint, etc) have some peculiarities that may prevent your cron jobs from executing; in particular, the files in /etc/cron.d, /etc/cron.{hourly,daily,weekly,monthly} must :
- be owned by root
- only be writable by root
- not be writable by group or other users
- have a name without any dots ‘.’ or any other special character but ‘-’ and ‘_’ .
- python issue run in crontab
- make sure python script have #!/usr/bin/python at the beginning, not neccessary
- make sure log the output, so you can debug in a smooth way
chmod to the script
- always run in normal user mode, not root user, and do not use
# don't do this
sudo contab -e
- if you try to put your log in other file, make sure the perssion of the file is good, some times, guys delete the log file via root user and create a new one with root user, this will cause the permission error.the right way is echo "" > logfile, then you won’t change the original file’s permission and group