Restoring Database from Physical Backup

Last updated: 2020-01-16 11:51:02

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Operation Scenario

The document describes how to restore a database on another server from a downloaded physical backup file.

Directions

Downloading a backup file

For more information on directions, see Backup Download.

Unpacking a backup file

  1. Backup files are compressed with qpress and then packaged with xbstream (a packing/unpacking tool offered by Percona). Therefore, after a backup file is downloaded, it should be unpacked using xbstream first. The xbstream tool can be downloaded from the official website of Percona XtraBackup. Alternatively, you can directly download a binary package.
  2. After XtraBackup is installed, run the xbstream command to unpack the backup file to the destination directory.
    xbstream -x -C /data < ~/test.xb
    The unpacking result is as shown below:
    extract.png

Decompressing a backup file

Backup files are compressed with the quicklz algorithm, so they need to be decompressed first before use. After downloading the qpress tool, you can extract qpress binary files by running the following command:

tar -xf qpress-11-linux-x64.tar -C /usr/local/bin
source /etc/profile

Then, decompress all .qp files in the destination directory by running the following qpress command:

xtrabackup --decompress --target-dir=/data
  • xtrabackup --decompress will call the qpress tool which should be installed before using the --decompress parameter.
  • The --remove-original options is supported only in Percona Xtrabackup v2.4.6 and higher.
  • xtrabackup won't delete the original files during decompression by default. If you want to delete them upon the completion of decompression, add the --remove-original parameter to the above command.

decompress.png

Preparing a backup file

After a backup file is decompressed, you need to execute the "apply log" operation by running the following command.

xtrabackup --prepare  --target-dir=/data

If the execution result contains the following output, it means that the preparation succeeded.
prepare.png

Modifying a configuration file

Given the existing version issues, the following parameters need to be commented out from the extracted file "backup-my.cnf".

  • innodb_checksum_algorithm
  • innodb_log_checksum_algorithm
  • innodb_fast_checksum
  • innodb_page_size
  • innodb_log_block_size
  • redo_log_version

Modifying file properties

Modify file properties and check whether files are owned by a TencentDB for MySQL user.

chown -R mysql:mysql /data

Starting the mysqld process and logging in for verification

  1. Start the mysqld process.
    mysqld_safe --defaults-file=/data/backup-my.cnf --user=mysql --datadir=/data &
  2. Log in to the client for verification.
    mysql  -uroot
  • After restoration, the table "mysql.user" doesn't contain TencentDB users, which should be created.
  • The following SQL statements should be executed before creating a user:
delete from mysql.db where user<>'root' and char_length(user)>0;
delete from mysql.tables_priv where user<>'root' and char_length(user)>0;
flush privileges;