mariadb-backup doesn't utilise innodb-undo-log-directory (if specified as a relative path) during copy-back operation

[root@localhost ~]# cat /etc/my.cnf.d/server.cnf

[server]

innodb_undo_tablespaces=2

innodb_undo_directory=./

log_error=/var/log/mysql/error.log

[root@localhost mysql]# mysql_install_db

Installing MariaDB/MySQL system tables in '/var/lib/mysql' ...

OK

To start mysqld at boot time you have to copy

support-files/mysql.server to the right place for your system

Two all-privilege accounts were created.

One is root@localhost, it has no password, but you need to

be system 'root' user to connect. Use, for example, sudo mysql

The second is root@localhost, it has no password either, but

you need to be the system 'root' user to connect.

After connecting you can set the password, if you would need to be

able to connect as any of these users with a password and without sudo

See the MariaDB Knowledgebase at https://mariadb.com/kb

You can start the MariaDB daemon with:

cd '/usr' ; /usr/bin/mysqld_safe --datadir='/var/lib/mysql'

You can test the MariaDB daemon with mysql-test-run.pl

cd '/usr/mysql-test' ; perl mysql-test-run.pl

Please report any problems at https://mariadb.org/jira

The latest information about MariaDB is available at https://mariadb.org/.

Consider joining MariaDB's strong and vibrant community:

https://mariadb.org/get-involved/

[root@localhost mysql]# ls

aria_log.00000001  aria_log_control  ib_buffer_pool  ibdata1  ib_logfile0  mysql  mysql_upgrade_info  performance_schema  sys  test  undo001  undo002

[root@localhost mysql]# mariadb-backup --print-defaults -uroot --target-dir=//mnt/mariadb-backup/ --backup

mariadb-backup would have been started with the following arguments:

--innodb_undo_tablespaces=2 --innodb_undo_directory=./ --log_error=/var/log/mysql/error.log -uroot --target-dir=//mnt/mariadb-backup/ --backup

[root@localhost mysql]# mariadb-backup  -uroot --target-dir=//mnt/mariadb-backup/ --backup

[00] 2022-03-28 18:29:11 Connecting to MySQL server host: localhost, user: root, password: not set, port: not set, socket: not set

mariadb-backup: Warning: Charset id '33' csname 'utf8mb3' trying to replace existing csname 'utf8'

mariadb-backup: Warning: Charset id '83' csname 'utf8mb3' trying to replace existing csname 'utf8'

[00] 2022-03-28 18:29:11 Using server version 10.7.3-MariaDB

mariadb-backup based on MariaDB server 10.7.3-MariaDB Linux (x86_64)

[00] 2022-03-28 18:29:11 uses posix_fadvise().

[00] 2022-03-28 18:29:11 cd to /var/lib/mysql/

[00] 2022-03-28 18:29:11 open files limit requested 0, set to 1024

[00] 2022-03-28 18:29:11 mariabackup: using the following InnoDB configuration:

[00] 2022-03-28 18:29:11 innodb_data_home_dir =

[00] 2022-03-28 18:29:11 innodb_data_file_path = ibdata1:12M:autoextend

[00] 2022-03-28 18:29:11 innodb_log_group_home_dir = ./

[00] 2022-03-28 18:29:11 InnoDB: Using Linux native AIO

2022-03-28 18:29:11 0 [Note] InnoDB: Number of pools: 1

2022-03-28 18:29:11 0 [Note] InnoDB: Opened 2 undo tablespaces

[00] 2022-03-28 18:29:11 mariabackup: Generating a list of tablespaces

[00] 2022-03-28 18:29:11 >> log scanned up to (42720)

[01] 2022-03-28 18:29:11 Copying ibdata1 to /mnt/mariadb-backup/ibdata1

[01] 2022-03-28 18:29:11         ...done

[01] 2022-03-28 18:29:11 Copying .//undo001 to /mnt/mariadb-backup/undo001

[01] 2022-03-28 18:29:12         ...done

[01] 2022-03-28 18:29:12 Copying .//undo002 to /mnt/mariadb-backup/undo002

[01] 2022-03-28 18:29:12         ...done

[01] 2022-03-28 18:29:12 Copying ./mysql/innodb_table_stats.ibd to /mnt/mariadb-backup/mysql/innodb_table_stats.ibd

[01] 2022-03-28 18:29:12         ...done

.....

[00] 2022-03-28 18:29:14 >> log scanned up to (42720)

[00] 2022-03-28 18:29:14 Executing BACKUP STAGE END

[00] 2022-03-28 18:29:14 All tables unlocked

[00] 2022-03-28 18:29:14 Copying ib_buffer_pool to /mnt/mariadb-backup/ib_buffer_pool

[00] 2022-03-28 18:29:14         ...done

[00] 2022-03-28 18:29:14 Backup created in directory '/mnt/mariadb-backup/'

[00] 2022-03-28 18:29:14 Writing backup-my.cnf

[00] 2022-03-28 18:29:14         ...done

[00] 2022-03-28 18:29:14 Writing xtrabackup_info

[00] 2022-03-28 18:29:14         ...done

[00] 2022-03-28 18:29:14 Redo log (from LSN 42708 to 42720) was copied.

[00] 2022-03-28 18:29:14 completed OK!

[root@localhost mysql]# mariadb-backup  -uroot --target-dir=//mnt/mariadb-backup/ --prepare

mariadb-backup based on MariaDB server 10.7.3-MariaDB Linux (x86_64)

[00] 2022-03-28 18:29:33 cd to /mnt/mariadb-backup/

[00] 2022-03-28 18:29:33 This target seems to be not prepared yet.

mariadb-backup: Warning: Charset id '33' csname 'utf8mb3' trying to replace existing csname 'utf8'

mariadb-backup: Warning: Charset id '83' csname 'utf8mb3' trying to replace existing csname 'utf8'

[00] 2022-03-28 18:29:33 mariabackup: using the following InnoDB configuration for recovery:

[00] 2022-03-28 18:29:33 innodb_data_home_dir = .

[00] 2022-03-28 18:29:33 innodb_data_file_path = ibdata1:12M:autoextend

[00] 2022-03-28 18:29:33 innodb_log_group_home_dir = .

[00] 2022-03-28 18:29:33 InnoDB: Using Linux native AIO

[00] 2022-03-28 18:29:33 Starting InnoDB instance for recovery.

[00] 2022-03-28 18:29:33 mariabackup: Using 104857600 bytes for buffer pool (set by --use-memory parameter)

2022-03-28 18:29:33 0 [Note] InnoDB: Uses event mutexes

2022-03-28 18:29:33 0 [Note] InnoDB: Compressed tables use zlib 1.2.7

2022-03-28 18:29:33 0 [Note] InnoDB: Number of pools: 1

2022-03-28 18:29:33 0 [Note] InnoDB: Using SSE4.2 crc32 instructions

2022-03-28 18:29:33 0 [Note] InnoDB: Initializing buffer pool, total size = 104857600, chunk size = 104857600

2022-03-28 18:29:33 0 [Note] InnoDB: Completed initialization of buffer pool

2022-03-28 18:29:33 0 [Note] InnoDB: Opened 2 undo tablespaces

2022-03-28 18:29:33 0 [Note] InnoDB: Starting crash recovery from checkpoint LSN=42708,42708

2022-03-28 18:29:33 0 [Note] InnoDB: Opened 2 undo tablespaces

[00] 2022-03-28 18:29:33 Last binlog file , position 0

[00] 2022-03-28 18:29:33 completed OK!

[root@localhost mysql]# ls

aria_log.00000001  ddl.log           ib_buffer_pool  ib_logfile0  localhost.pid      mysql       mysql_upgrade_info  sys   undo001

aria_log_control   ddl_recovery.log  ibdata1         ibtmp1       multi-master.info  mysql.sock  performance_schema  test  undo002

[root@localhost mysql]# rm -fr *

[root@localhost mysql]# ll

total 0

[root@localhost mysql]# systemctl stop mysql

[root@localhost mysql]# mariadb-backup --print-defaults -uroot --target-dir=//mnt/mariadb-backup/ --copy-back

mariadb-backup would have been started with the following arguments:

--innodb_undo_tablespaces=2 --innodb_undo_directory=./ --log_error=/var/log/mysql/error.log -uroot --target-dir=//mnt/mariadb-backup/ --copy-back

[root@localhost mysql]# rm -fr *

[root@localhost mysql]# mariadb-backup -uroot --target-dir=//mnt/mariadb-backup/ --copy-back

mariadb-backup based on MariaDB server 10.7.3-MariaDB Linux (x86_64)

mariadb-backup: Can't create file './undo001' (errno: 17 "File exists")

[01] 2022-03-28 18:30:40 error: cannot open the destination stream for undo001

[01] 2022-03-28 18:30:40 Error: copy_file() failed.

[root@localhost mysql]# mariadb-backup  -uroot --target-dir=//mnt/mariadb-backup/ --copy-back --innodb_undo_directory=./

mariadb-backup based on MariaDB server 10.7.3-MariaDB Linux (x86_64)

mariadb-backup: Can't create file './undo001' (errno: 17 "File exists")

[01] 2022-03-28 19:27:58 error: cannot open the destination stream for undo001

[01] 2022-03-28 19:27:58 Error: copy_file() failed.

[root@localhost mysql]# mariadb-backup  -uroot --target-dir=//mnt/mariadb-backup/ --copy-back --innodb_undo_directory=/var/lib/mysql/

mariadb-backup based on MariaDB server 10.7.3-MariaDB Linux (x86_64)

[01] 2022-03-28 19:26:52 Copying undo001 to /var/lib/mysql/undo001

[01] 2022-03-28 19:26:52         ...done

[01] 2022-03-28 19:26:52 Copying undo002 to /var/lib/mysql/undo002

[01] 2022-03-28 19:26:52         ...done

[01] 2022-03-28 19:26:52 Copying ibdata1 to /var/lib/mysql/./ibdata1

[01] 2022-03-28 19:26:52         ...done

[01] 2022-03-28 19:26:52 Copying ./mysql/innodb_table_stats.ibd to /var/lib/mysql/mysql/innodb_table_stats.ibd

[01] 2022-03-28 19:26:52         ...done

[01] 2022-03-28 19:26:52 Copying ./mysql/innodb_index_stats.ibd to /var/lib/mysql/mysql/innodb_index_stats.ibd

[01] 2022-03-28 19:26:52         ...done

....

[01] 2022-03-28 19:26:52 Copying ./ib_buffer_pool to /var/lib/mysql/ib_buffer_pool

[01] 2022-03-28 19:26:52         ...done

[01] 2022-03-28 19:26:52 Copying ./xtrabackup_info to /var/lib/mysql/xtrabackup_info

[01] 2022-03-28 19:26:52         ...done

[00] 2022-03-28 19:26:52 completed OK!