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8.10 `mysqldump' -- A Database Backup Program
=============================================
The `mysqldump' client is a backup program originally written by Igor
Romanenko. It can be used to dump a database or a collection of
databases for backup or for transferring the data to another SQL server
(not necessarily a MySQL server). The dump contains SQL statements to
create the table or populate it, or both.
If you are doing a backup on the server, and your tables all are
`MyISAM' tables, consider using the `mysqlhotcopy' instead because it
can accomplish faster backups and faster restores. See
mysqlhotcopy.
There are three general ways to invoke `mysqldump':
shell> mysqldump [OPTIONS] DB_NAME [TABLES]
shell> mysqldump [OPTIONS] --databases DB_NAME1 [DB_NAME2 DB_NAME3...]
shell> mysqldump [OPTIONS] --all-databases
If you do not name any tables following DB_NAME or if you use the
-databases or -all-databases option, entire databases are dumped.
To get a list of the options your version of `mysqldump' supports,
execute `mysqldump --help'.
If you run `mysqldump' without the -quick or -opt option, `mysqldump'
loads the whole result set into memory before dumping the result. This
can be a problem if you are dumping a big database. The -opt option is
enabled by default, but can be disabled with -skip-opt.
If you are using a recent copy of the `mysqldump' program to generate a
dump to be reloaded into a very old MySQL server, you should not use the
-opt or -extended-insert option. Use -skip-opt instead.
`mysqldump' supports the following options:
* -help, -?
Display a help message and exit.
* -add-drop-database
Add a `DROP DATABASE' statement before each `CREATE DATABASE'
statement.
* -add-drop-table
Add a `DROP TABLE' statement before each `CREATE TABLE' statement.
* -add-locks
Surround each table dump with `LOCK TABLES' and `UNLOCK TABLES'
statements. This results in faster inserts when the dump file is
reloaded. See insert-speed.
* -all-databases, -A
Dump all tables in all databases. This is the same as using the
-databases option and naming all the databases on the command line.
* -allow-keywords
Allow creation of column names that are keywords. This works by
prefixing each column name with the table name.
* -character-sets-dir=PATH
The directory where character sets are installed. See
character-sets.
* -comments, -i
Write additional information in the dump file such as program
version, server version, and host. . This option is enabled by
default. To suppress additional, use -skip-comments.
* -compact
Produce less verbose output. This option suppresses comments and
enables the -skip-add-drop-table, -no-set-names,
-skip-disable-keys, and -skip-add-locks options.
* -compatible=NAME
Produce output that is more compatible with other database systems
or with older MySQL servers. The value of `name' can be `ansi',
`mysql323', `mysql40', `postgresql', `oracle', `mssql', `db2',
`maxdb', `no_key_options', `no_table_options', or
`no_field_options'. To use several values, separate them by
commas. These values have the same meaning as the corresponding
options for setting the server SQL mode. See
server-sql-mode.
This option does not guarantee compatibility with other servers.
It only enables those SQL mode values that are currently available
for making dump output more compatible. For example,
-compatible=oracle does not map data types to Oracle types or use
Oracle comment syntax.
* -complete-insert, -c
Use complete `INSERT' statements that include column names.
* -compress, -C
Compress all information sent between the client and the server if
both support compression.
* -create-options
Include all MySQL-specific table options in the `CREATE TABLE'
statements.
* -databases, -B
Dump several databases. Normally, `mysqldump' treats the first name
argument on the command line as a database name and following
names as table names. With this option, it treats all name
arguments as database names. `CREATE DATABASE' and `USE'
statements are included in the output before each new database.
* -debug[=DEBUG_OPTIONS], -# [DEBUG_OPTIONS]
Write a debugging log. The DEBUG_OPTIONS string is often
`'d:t:o,FILE_NAME''. The default is
`'d:t:o,/tmp/mysqldump.trace''.
* -default-character-set=CHARSET_NAME
Use CHARSET_NAME as the default character set. See
character-sets. If not specified, `mysqldump' uses `utf8'.
* -delayed-insert
Write `INSERT DELAYED' statements rather than `INSERT' statements.
* -delete-master-logs
On a master replication server, delete the binary logs after
performing the dump operation. This option automatically enables
-master-data.
* -disable-keys, -K
For each table, surround the `INSERT' statements with `/*!40000
ALTER TABLE TBL_NAME DISABLE KEYS */;' and `/*!40000 ALTER TABLE
TBL_NAME ENABLE KEYS */;' statements. This makes loading the dump
file faster because the indexes are created after all rows are
inserted. This option is effective for `MyISAM' tables only.
* -extended-insert, -e
Use multiple-row `INSERT' syntax that include several `VALUES'
lists. This results in a smaller dump file and speeds up inserts
when the file is reloaded.
* -fields-terminated-by=..., -fields-enclosed-by=...,
-fields-optionally-enclosed-by=..., -fields-escaped-by=...,
-lines-terminated-by=...
These options are used with the -T option and have the same
meaning as the corresponding clauses for `LOAD DATA INFILE'. See
load-data.
* -first-slave, -x
Deprecated. Now renamed to -lock-all-tables.
* -flush-logs, -F
Flush the MySQL server log files before starting the dump. This
option requires the `RELOAD' privilege. Note that if you use this
option in combination with the -all-databases (or -A) option, the
logs are flushed _for each database dumped_. The exception is when
using -lock-all-tables or -master-data: In this case, the logs are
flushed only once, corresponding to the moment that all tables are
locked. If you want your dump and the log flush to happen at
exactly the same moment, you should use -flush-logs together with
either -lock-all-tables or -master-data.
* -force, -f
Continue even if an SQL error occurs during a table dump.
* -host=HOST_NAME, -h HOST_NAME
Dump data from the MySQL server on the given host. The default
host is `localhost'.
* -hex-blob
Dump binary columns using hexadecimal notation (for example,
`'abc'' becomes `0x616263'). The affected data types are `BINARY',
`VARBINARY', and `BLOB'. As of MySQL 5.0.13, `BIT' columns are
affected as well.
* -ignore-table=DB_NAME.TBL_NAME
Do not dump the given table, which must be specified using both
the database and table names. To ignore multiple tables, use this
option multiple times.
* -insert-ignore
Write `INSERT' statements with the `IGNORE' option.
* -lock-all-tables, -x
Lock all tables across all databases. This is achieved by
acquiring a global read lock for the duration of the whole dump.
This option automatically turns off -single-transaction and
-lock-tables.
* -lock-tables, -l
Lock all tables before starting the dump. The tables are locked
with `READ LOCAL' to allow concurrent inserts in the case of
`MyISAM' tables. For transactional tables such as `InnoDB' and
`BDB', -single-transaction is a much better option, because it
does not need to lock the tables at all.
Please note that when dumping multiple databases, -lock-tables
locks tables for each database separately. So, this option does
not guarantee that the tables in the dump file are logically
consistent between databases. Tables in different databases may be
dumped in completely different states.
* -master-data[=VALUE]
Write the binary log filename and position to the output. This
option requires the `RELOAD' privilege and the binary log must be
enabled. If the option value is equal to 1, the position and
filename are written to the dump output in the form of a `CHANGE
MASTER' statement that makes a slave server start from the correct
position in the master's binary logs if you use this SQL dump of
the master to set up a slave. If the option value is equal to 2,
the `CHANGE MASTER' statement is written as an SQL comment. This
is the default action if VALUE is omitted.
The -master-data option turns on -lock-all-tables, unless
-single-transaction also is specified (in which case, a global
read lock is only acquired a short time at the beginning of the
dump. See also the description for -single-transaction. In all
cases, any action on logs happens at the exact moment of the dump.
This option automatically turns off -lock-tables.
* -no-autocommit
Enclose the `INSERT' statements for each dumped table within `SET
AUTOCOMMIT=0' and `COMMIT' statements.
* -no-create-db, -n
This option suppresses the `CREATE DATABASE' statements that are
otherwise included in the output if the -databases or
-all-databases option is given.
* -no-create-info, -t
Do not write `CREATE TABLE' statements that re-create each dumped
table.
* -no-data, -d
Do not write any row information for the table. This is very
useful if you want to dump only the `CREATE TABLE' statement for
the table.
* -opt
This option is shorthand; it is the same as specifying
-add-drop-table -add-locks -create-options -disable-keys
-extended-insert -lock-tables -quick -set-charset. It should give
you a fast dump operation and produce a dump file that can be
reloaded into a MySQL server quickly.
_This option is enabled by default, but can be disabled with
-skip-opt_. To disable only certain of the options enabled by
-opt, use their -skip forms; for example, -skip-add-drop-table or
-skip-quick.
* -order-by-primary
Sorts each table's rows by its primary key, or its first unique
index, if such an index exists. This is useful when dumping a
`MyISAM' table to be loaded into an `InnoDB' table, but will make
the dump itself take considerably longer.
* -password[=PASSWORD], -p[PASSWORD]
The password to use when connecting to the server. If you use the
short option form (-p), you _cannot_ have a space between the
option and the password. If you omit the PASSWORD value following
the -password or -p option on the command line, you are prompted
for one.
Specifying a password on the command line should be considered
insecure. See password-security.
* -port=PORT_NUM, -P PORT_NUM
The TCP/IP port number to use for the connection.
* -protocol={TCP|SOCKET|PIPE|MEMORY}
The connection protocol to use.
* -quick, -q
This option is useful for dumping large tables. It forces
`mysqldump' to retrieve rows for a table from the server a row at
a time rather than retrieving the entire row set and buffering it
in memory before writing it out.
* -quote-names, -Q
Quote database, table, and column names within ‘``'’
characters. If the `ANSI_QUOTES' SQL mode is enabled, names are
quoted within ‘`"'’ characters. This option is enabled by
default. It can be disabled with -skip-quote-names, but this
option should be given after any option such as -compatible that
may enable -quote-names.
* -result-file=FILE, -r FILE
Direct output to a given file. This option should be used on
Windows to prevent newline ‘`\n'’ characters from being
converted to ‘`\r\n'’ carriage return/newline sequences.
* -routines, -R
Dump stored routines (functions and procedures) from the dumped
databases. The output generated by using --routines contains
`CREATE PROCEDURE' and `CREATE FUNCTION' statements to re-create
the routines. However, these statements do not include attributes
such as the routine definer or the creation and modification
timestamps. This means that when the routines are reloaded, they
will be created with the definer set to the reloading user and
timestamps equal to the reload time.
If you require routines to be re-created with their original
definer and timestamp attributes, do not use -routines. Instead,
dump and reload the contents of the `mysql.proc' table directly,
using a MySQL account that has appropriate privileges for the
`mysql' database.
This option was added in MySQL 5.0.13. Before that, stored
routines are not dumped.
* -set-charset
Add `SET NAMES DEFAULT_CHARACTER_SET' to the output. This option
is enabled by default. To suppress the `SET NAMES' statement, use
-skip-set-charset.
* -single-transaction
This option issues a `BEGIN' SQL statement before dumping data
from the server. It is useful only with transactional tables such
as `InnoDB' and `BDB', because then it dumps the consistent state
of the database at the time when `BEGIN' was issued without
blocking any applications.
When using this option, you should keep in mind that only `InnoDB'
tables are dumped in a consistent state. For example, any `MyISAM'
or `HEAP' tables dumped while using this option may still change
state.
The -single-transaction option and the -lock-tables option are
mutually exclusive, because `LOCK TABLES' causes any pending
transactions to be committed implicitly.
To dump big tables, you should combine this option with -quick.
* -socket=PATH, -S PATH
For connections to `localhost', the Unix socket file to use, or,
on Windows, the name of the named pipe to use.
* -skip-comments
See the description for the -comments option.
* -tab=PATH, -T PATH
Produce tab-separated data files. For each dumped table,
`mysqldump' creates a `TBL_NAME.sql' file that contains the
`CREATE TABLE' statement that creates the table, and a
`TBL_NAME.txt' file that contains its data. The option value is the
directory in which to write the files.
By default, the `.txt' data files are formatted using tab
characters between column values and a newline at the end of each
line. The format can be specified explicitly using the -fields-XXX
and -lines-XXX options.
* This option should be used only when `mysqldump' is run on
the same machine as the `mysqld' server. You must have the `FILE'
privilege, and the server must have permission to write files in
the directory that you specify.
* -tables
Override the -databases or -B option. All name arguments following
the option are regarded as table names.
* -triggers
Dump triggers for each dumped table. This option is enabled by
default; disable it with -skip-triggers. This option was added in
MySQL 5.0.11. Before that, triggers are not dumped.
* -tz-utc
Add `SET TIME_ZONE='+00:00'' to the dump file so that `TIMESTAMP'
columns can be dumped and reloaded between servers in different
time zones. Without this option, `TIMESTAMP' columns are dumped
and reloaded in the time zones local to the source and destination
servers, which can cause the values to change. -tz-utc also
protects against changes due to daylight saving time. -tz-utc is
enabled by default. To disable it, use -skip-tz-utc. This option
was added in MySQL 5.0.15.
* -user=USER_NAME, -u USER_NAME
The MySQL username to use when connecting to the server.
* -verbose, -v
Verbose mode. Print more information about what the program does.
* -version, -V
Display version information and exit.
* -where='WHERE_CONDITION', -w 'WHERE_CONDITION'
Dump only rows selected by the given `WHERE' condition. Note that
quotes around the condition are mandatory if it contains spaces or
other characters that are special to your command interpreter.
Examples:
--where="user='jimf'"
-w"userid>1"
-w"userid<1"
* -xml, -X
Write dump output as well-formed XML.
You can also set the following variables by using -VAR_NAME=VALUE
syntax:
* `max_allowed_packet'
The maximum size of the buffer for client/server communication.
The maximum is 1GB.
* `net_buffer_length'
The initial size of the buffer for client/server communication.
When creating multiple-row-insert statements (as with option
-extended-insert or -opt), `mysqldump' creates rows up to
`net_buffer_length' length. If you increase this variable, you
should also ensure that the `net_buffer_length' variable in the
MySQL server is at least this large.
It is also possible to set variables by using
-set-variable=VAR_NAME=VALUE or -O VAR_NAME=VALUE syntax. _This syntax
is deprecated_.
The most common use of `mysqldump' is probably for making a backup of
an entire database:
shell> mysqldump --opt DB_NAME > BACKUP-FILE.SQL
You can read the dump file back into the server like this:
shell> mysql DB_NAME < BACKUP-FILE.SQL
Or like this:
shell> mysql -e "source /PATH-TO-BACKUP/BACKUP-FILE.SQL" DB_NAME
`mysqldump' is also very useful for populating databases by copying
data from one MySQL server to another:
shell> mysqldump --opt DB_NAME | mysql --host=REMOTE_HOST -C DB_NAME
It is possible to dump several databases with one command:
shell> mysqldump --databases DB_NAME1 [DB_NAME2 ...] > my_databases.sql
To dump all databases, use the -all-databases option:
shell> mysqldump --all-databases > all_databases.sql
For `InnoDB' tables, `mysqldump' provides a way of making an online
backup:
shell> mysqldump --all-databases --single-transaction > all_databases.sql
This backup just needs to acquire a global read lock on all tables
(using `FLUSH TABLES WITH READ LOCK') at the beginning of the dump. As
soon as this lock has been acquired, the binary log coordinates are
read and the lock is released. If and only if one long updating
statement is running when the `FLUSH' statement is issued, the MySQL
server may get stalled until that long statement finishes, and then the
dump becomes lock-free. If the update statements that the MySQL server
receives are short (in terms of execution time), the initial lock
period should not be noticeable, even with many updates.
For point-in-time recovery (also known as `roll-forward,' when you need
to restore an old backup and replay the changes that happened since that
binary-log::) or at least know the binary log coordinates to which the
dump corresponds:
shell> mysqldump --all-databases --master-data=2 > all_databases.sql
Or:
shell> mysqldump --all-databases --flush-logs --master-data=2
> all_databases.sql
The simultaneous use of -master-data and -single-transaction provides a
convenient way to make an online backup suitable for point-in-time
recovery if tables are stored in the `InnoDB' storage engine.
For more information on making backups, see backup, and
backup-strategy-example.
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