Now that we can take advantage of rsync to minimize the data to transfer when backup. But it's still a little uncomfortable if we need to do this manually everyday, right? Well, cron is here to solve the pain.
Cron is kind of a system service that automatically do some job as you specified. Backup, for example, is a perfect kind of job that we can count on cron.
First, we need to specify a job that we want cron to do. In my case, I want cron to automatically sync my source tree folder on remote data center and my local backup folder. A simple rsync command seems meet my need. But actually, there are more to consider:
-
I don't want to copy the obj files, since they are normally large in size and change frequently, but can be easily re-generated. But I also don't want to skip the entire build folder when do rsync since there are some configure files in there.
-
The backup process should be totally automated. More specifically, no password is needed when do rysnc.
Towards the first need, I can use ssh to send remote command to do necessary clean up work before rysnc. And the second need can be meted according to my previous post about ssh/scp without password.
So my final backup script looks like this:
#!/bin/sh
# ~/backup.sh
LOG_FILE=~/backup.log
SOURCE_DIR=b@B:~/src/
TARGET_DIR=~/src_backup
date >> $LOG_FILE
echo "Synchronization start..." >> $LOG_FILE
ssh b@B 'cd ~/src/build; make clean; rm -rf obj/" >> $LOG_FILE
rsync -avz --exclude "tags" $SOURCE_DIR $TARGET_DIR >> $LOG_FILE
echo "Synchronization done" >> $LOG_FILE
Once we figure out what to do, we need to tell cron about our job. The
configure file of cron is /etc/crontab. A job description is like follows:
# 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 0 0 * * * jack ~/backup.sh
I want to do backup every day on midnight so I set the minute and hour both to
0. The asterisk (*) symbol in day/month means any valid values.
Now we are done. The back up process is completely automated and scheduled.
Reference:
http://myhowtosandprojects.blogspot.hk/2008/07/sincronize-folders-with-rsync-using-ssh.html