Implementation method of Crontab automatic backup Web site in CentOS

Crontab Introduction

The crontab command is common in UNIX and unix-based operating systems, and is used to set periodically executed instructions. This command reads the instruction from the standard input device and stores it in a "crontab" file for later reading and execution.　　The word derives from the Greek chronos (χρνο), which is intended to be time. Typically, crontab stored instructions are activated by the daemon, Crond often run in the background, checking every minute for scheduled jobs to be performed. This type of assignment is commonly referred to as cron jobs.

Crontab usage

The crontab format is as follows:

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F1 F2 F3 f4 f5 program

Where F1 is the minute, F2 represents the Hour, F3 represents the day of the month, the F4 represents the month, and the F5 represents the day of the one week. The program represents the path to execute.

When F1 is *, the PROGRAM,F2 is executed every minute for *, which means that the program is executed hourly, and the rest of the analogy
When F1 is a-b to be executed from the time of the first a minute to the B minute, the F2 is a-b to execute from a to B hours, and the rest by analogy
When F1 is */n, it is executed once every n minutes, F2 is performed once per N-hour intervals for */n, and the rest by analogy
When F1 is a, B, C,... The first A, B, C,... Minutes to execute, F2 for a, B, C,... The first is a, B, c ... An hour to execute, the rest of the analogy
Admin login ssh, enter command crontab-e edit crontab file, enter and save according to the format above.

Here's a common backup method:

1. File backup

Compress files for backup using the TAR command:

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#tar-ZCVF backup.tar.gz Dir1

Dir1 for the directory or file to be backed up
Backup RESTORE command:

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#tar-ZXVF backup.tar.gz

2. Database backup

Most database systems have commands to support backup and recovery of databases. For example, MySQL, the database backup command is:

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#mysqldump-host=dbhost-user=username-password=password dbname > Db.dump The restore command for the MySQL backup is: #mysql-host=dbhost-user=username-password=password dbname < Db.dump

3. Automatic Task Scheduled backup

Use the above command to write a backup script (such as/home/backup/backup.sh), and then use the CRONTAB-E command to edit the timed task, the following is the day 01:30 automatic backup example

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* * * */home/backup/backup.sh

4. Name of backup file

You can automatically add a backup time to a daily backup file name, and here is a sample script:

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#!/bin/ Bash curr= ' date +%y%m%d%h%m%s ' tar czvf backup_$curr.tar.gz dir1 dir2 Mysqldump-host=dbhost-user=username- Password=password dbname > Db_$curr.dump