How to make a script execute regularly

I. Planning tasks

1. Non-root users create scheduled tasks

Crontab-u bin-e

Crondtab-u bin-l / / View method

Ls / var/spool/cron/ all scheduled tasks are stored in directory

two。 Advanced crontab, tampering with a system-level scheduled task

Ls / etc/cron / / double press the tab key to view

Cron.d/ # scheduled tasks at the system level

The cron.daily/ # system performs scheduled tasks every day

The cron.hourly/ # system performs scheduled tasks every hour

The cron.monthly/ # system performs scheduled tasks every month

The cron.weekly/ # system performs scheduled tasks every week

Find / etc/cron* / / View scheduled tasks that can be added at the system level

Case: add a system-level * program

Vim / etc/cron.daily/tmpwatch / / add at the end of the script that periodically deletes temporary files in the / tmp directory

Echo aaa

Troubleshooting method: use md5sum to verify the integrity of the file. The MD5 is different before and after script modification.

Syntax: md5sum fil

Generate MD5 values for all files under / etc/cron*

Find / etc/cron*-type f-exec md5sum {}\; > / usr/share/file_md5.v1 / / generate ahead of time, if forgotten, operate from the new machine

Find / etc/cron*-type f-exec md5sum {}\; > / usr/share/file_md5.v2 / / if you suspect a problem, generate

Diff / tmp/file_md5.v1 / tmp/file_md5.v2 / / comparison of the last two

Note: 1 * / / is the first minute of every hour!

2. Boot and start

1. / etc/rc.local / / add a * * script to the boot script

Troubleshooting method: filter out blank lines when displayed

Grep-v ^ $/ etc/rc.local / / ^ $# begins with a blank and ends with an empty line. -v # indicates inversion, showing

Note: be sure to cat, do not use vim, because some * * will deliberately add a lot of blank lines to the rc.local and add a script in the middle or at the end

two。 Use the boot server script to load * programs, such as httpd (apache web server startup script), and even more powerful * write a boot startup program by yourself.

The script files in the ls / etc/init.d/ directory are all script files that can be booted and started.

Troubleshooting method:

Method 1: compare the good configuration files of other servers and use the MD5 value to do the comparison

Method 2: view the files that were generated or modified on the same day

Find / etc/init.d/-mtime-1 / / View files that have been modified from the previous day to the present

Third, the system command is replaced by someone, set a trigger event

Troubleshooting method: use rpm to check the integrity of files

Syntax: name of rpm-V package / / use rpm to check file integrity

Absolute path of the rpm-Vf command / / use rpm to check the integrity of the command

Rpm-Va / / check all rpm installed software packages and see if the generation commands or files have been changed

Description:

S file Size size is inconsistent

M Mode model is inconsistent (including licenses and file types)

5 MD5 sum checksum inconsistency

D Device master-slave device number mismatch

L readLink path mismatch

U User genus and master are inconsistent

G Group belongs to different groups

T mTime modification time is inconsistent