Linux Delete files in-depth understanding and task timing--linux alarms

1. Linux Delete a file's permissions to see the directory where the files are located
Delete files need to have W permission on this directory

Modifying a file to view the contents of a file requires RW permission on the file

Delete Create a file needs to have WX permission on the file to be seated in the directory
2. chattr Add hidden file lsattr view hidden permissions append append permission can only append
I indestructible cannot be modified unable to delete some files that need to be protected for the system can be added Eg:/etc/inittab/etc/passwd/etc/shadow

3. Suid running a command is equivalent to root and special permissions chmod u+s/bin/rm Super dangerous.

chmod o+t/tmp Sticky bit--anyone can create, but only manage their own




Linux timed Tasks!! Alarm clock!!
ATD Run Once
No
Anacron Server for non-7x24 hours

Crond the user's scheduled tasks, and the system's scheduled tasks

System timing tasks do not require drill down
　　

We call the user a timed task.

View Task Crontab-l Cat/var spool/cron/root
Edit Task Crontab-e Vim/var spool/cron/root
1,!! Whether the software that the timer task depends on can be used
/etc/init.d/crond status
2. See if Crond is powered on
Chkconfig | grep Crond
3 to see if sshd is running
Ps-ef |grep sshd

Process: A program that is running
Daemon: A program that runs continuously




Crontab How to use: Have grammar check function
View Task Crontab-l Cat/var spool/cron/root
Edit Task Crontab-e Vim/var spool/cron/root
Directory for timed file placement:/var/spool/cron/
Log files for timed tasks:/var/log/cron
What is forbidden with the use of timed tasks/etc/cron/

Timing task is what time to do what task!

* EVERY * * * * * command
/n */10 means every 10 minutes
Ntpdate ntp1.aliyun.com
CRONTAB-E * * * * * */usr/sbin/ntpdate ntp1.aliyun.com >/dev/null 2>$1
-07-11 * * * cmd runs once a day from 7 o'clock in the morning to 11.
Every Monday Friday three o'clock in the morning to five point of the hour and the slightest run
Timeshare Zhou
00,3003-05**01-05

Linux Delete files in-depth understanding and task timing--linux alarms