在这里写了很多篇linux，习惯了在这里写
centos中定时任务命令是crond
ubuntu中定时任务命令是cron
这两种linux系统不一样的地方还是挺多的，
既然我目前的专注点是ubuntu，所以centos就放下
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date -s 17：39：50 在centos中能对当前时间继续修改
但是在ubuntu中不行
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root@ubuntuE:/home/sophie# crontab -e
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ubuntu 没有 centos中的 /var/log/crond
解决方法
http://askubuntu.com/questions/56683/where-is-the-cron-crontab-log
On a default installation the cron jobs get logged to
/var/log/syslog You can see just cron jobs in that logfile by running
grep CRON /var/log/syslog If you haven't reconfigured anything,the entries will be in there.
-----or
You can create a cron.log file to contain just the CRON entries that show up in syslog. Note that CRON jobs will still show up in syslog if you follow the following directions.
Open the file
/etc/rsyslog.d/50-default.conf Find the line that starts with:
#cron.* uncomment that line, save the file, and restart rsyslog:
sudo service rsyslog restart You should now see a cron log file here:
/var/log/cron.log Cron activity will now be logged to this file (in addition to syslog).
Note that in cron.log you will see entries for when cron ran scripts in /etc/cron.hourly, cron.daily, etc. - e.g. something like:
Apr 12 14:17:01 cd CRON[14368]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) However, you will not see more information about what scripts were actually ran inside /etc/cron.daily or /etc/cron.hourly, unless those scripts direct output to the cron.log (or perhaps to some other log file).
If you want to verify if a crontab is running and not have to search for it in cron.log or syslog, create a crontab that redirects output to a log file of your choice - something like:
01 14 * * * /home/joe/myscript >> /home/log/myscript.log 2>&1 This will redirect all standard output and errors that may be produced by the script that is run to the log file specified.