PG_RECEIVEWAL(1) PostgreSQL 18.6 Documentation PG_RECEIVEWAL(1) NAME pg_receivewal - stream write-ahead logs from a PostgreSQL server SYNOPSIS pg_receivewal [option...] DESCRIPTION pg_receivewal is used to stream the write-ahead log from a running Post- greSQL cluster. The write-ahead log is streamed using the streaming repli- cation protocol, and is written to a local directory of files. This direc- tory can be used as the archive location for doing a restore using point-in-time recovery (see Section 25.3). pg_receivewal streams the write-ahead log in real time as it's being gener- ated on the server, and does not wait for segments to complete like archive_command and archive_library do. For this reason, it is not neces- sary to set archive_timeout when using pg_receivewal. Unlike the WAL receiver of a PostgreSQL standby server, pg_receivewal by default flushes WAL data only when a WAL file is closed. The option --syn- chronous must be specified to flush WAL data in real time. Since pg_re- ceivewal does not apply WAL, you should not allow it to become a synchro- nous standby when synchronous_commit equals remote_apply. If it does, it will appear to be a standby that never catches up, and will cause transac- tion commits to block. To avoid this, you should either configure an appro- priate value for synchronous_standby_names, or specify application_name for pg_receivewal that does not match it, or change the value of synchro- nous_commit to something other than remote_apply. The write-ahead log is streamed over a regular PostgreSQL connection and uses the replication protocol. The connection must be made with a user hav- ing REPLICATION permissions (see Section 21.2) or a superuser, and pg_hba.conf must permit the replication connection. The server must also be configured with max_wal_senders set high enough to leave at least one ses- sion available for the stream. The starting point of the write-ahead log streaming is calculated when pg_receivewal starts: 1. First, scan the directory where the WAL segment files are written and find the newest completed segment file, using as the starting point the beginning of the next WAL segment file. 2. If a starting point cannot be calculated with the previous method, and if a replication slot is used, an extra READ_REPLICATION_SLOT command is issued to retrieve the slot's restart_lsn to use as the starting point. This option is only available when streaming write-ahead logs from PostgreSQL 15 and up. 3. If a starting point cannot be calculated with the previous method, the latest WAL flush location is used as reported by the server from an IDENTIFY_SYSTEM command. If the connection is lost, or if it cannot be initially established, with a non-fatal error, pg_receivewal will retry the connection indefinitely, and reestablish streaming as soon as possible. To avoid this behavior, use the -n parameter. In the absence of fatal errors, pg_receivewal will run until terminated by the SIGINT (Control+C) or SIGTERM signal. OPTIONS -D directory --directory=directory Directory to write the output to. This parameter is required. -E lsn --endpos=lsn Automatically stop replication and exit with normal exit status 0 when receiving reaches the specified LSN. If there is a record with LSN exactly equal to lsn, the record will be processed. --if-not-exists Do not error out when --create-slot is specified and a slot with the specified name already exists. -n --no-loop Don't loop on connection errors. Instead, exit right away with an er- ror. --no-sync This option causes pg_receivewal to not force WAL data to be flushed to disk. This is faster, but means that a subsequent operating system crash can leave the WAL segments corrupt. Generally, this option is useful for testing but should not be used when doing WAL archiving on a production deployment. This option is incompatible with --synchronous. -s interval --status-interval=interval Specifies the number of seconds between status packets sent back to the server. This allows for easier monitoring of the progress from server. A value of zero disables the periodic status updates completely, al- though an update will still be sent when requested by the server, to avoid timeout disconnect. The default value is 10 seconds. -S slotname --slot=slotname Require pg_receivewal to use an existing replication slot (see Sec- tion 26.2.6). When this option is used, pg_receivewal will report a flush position to the server, indicating when each segment has been synchronized to disk so that the server can remove that segment if it is not otherwise needed. When the replication client of pg_receivewal is configured on the server as a synchronous standby, then using a replication slot will re- port the flush position to the server, but only when a WAL file is closed. Therefore, that configuration will cause transactions on the primary to wait for a long time and effectively not work satisfacto- rily. The option --synchronous (see below) must be specified in addi- tion to make this work correctly. --synchronous Flush the WAL data to disk immediately after it has been received. Also send a status packet back to the server immediately after flushing, re- gardless of --status-interval. This option should be specified if the replication client of pg_re- ceivewal is configured on the server as a synchronous standby, to en- sure that timely feedback is sent to the server. -v --verbose Enables verbose mode. -Z level -Z method[:detail] --compress=level --compress=method[:detail] Enables compression of write-ahead logs. The compression method can be set to gzip, lz4 (if PostgreSQL was com- piled with --with-lz4) or none for no compression. A compression detail string can optionally be specified. If the detail string is an integer, it specifies the compression level. Otherwise, it should be a comma-separated list of items, each of the form keyword or key- word=value. Currently, the only supported keyword is level. If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algo- rithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0. The suffix .gz will automatically be added to all filenames when using gzip, and the suffix .lz4 is added when using lz4. The following command-line options control the database connection parame- ters. -d connstr --dbname=connstr Specifies parameters used to connect to the server, as a connection string; these will override any conflicting command line options. This option is called --dbname for consistency with other client appli- cations, but because pg_receivewal doesn't connect to any particular database in the cluster, any database name included in the connection string will be ignored by the server. However, a database name supplied that way overrides the default database name (replication) for purposes of looking up the replication connection's password in ~/.pgpass. Simi- larly, middleware or proxies used in connecting to PostgreSQL might utilize the name for purposes such as connection routing. -h host --host=host Specifies the host name of the machine on which the server is running. If the value begins with a slash, it is used as the directory for the Unix domain socket. The default is taken from the PGHOST environment variable, if set, else a Unix domain socket connection is attempted. -p port --port=port Specifies the TCP port or local Unix domain socket file extension on which the server is listening for connections. Defaults to the PGPORT environment variable, if set, or a compiled-in default. -U username --username=username User name to connect as. -w --no-password Never issue a password prompt. If the server requires password authen- tication and a password is not available by other means such as a .pg- pass file, the connection attempt will fail. This option can be useful in batch jobs and scripts where no user is present to enter a password. -W --password Force pg_receivewal to prompt for a password before connecting to a database. This option is never essential, since pg_receivewal will automatically prompt for a password if the server demands password authentication. However, pg_receivewal will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt. pg_receivewal can perform one of the two following actions in order to con- trol physical replication slots: --create-slot Create a new physical replication slot with the name specified in --slot, then exit. --drop-slot Drop the replication slot with the name specified in --slot, then exit. Other options are also available: -V --version Print the pg_receivewal version and exit. -? --help Show help about pg_receivewal command line arguments, and exit. EXIT STATUS pg_receivewal will exit with status 0 when terminated by the SIGINT or SIGTERM signal. (That is the normal way to end it. Hence it is not an er- ror.) For fatal errors or other signals, the exit status will be nonzero. ENVIRONMENT This utility, like most other PostgreSQL utilities, uses the environment variables supported by libpq (see Section 32.15). The environment variable PG_COLOR specifies whether to use color in diag- nostic messages. Possible values are always, auto and never. NOTES When using pg_receivewal instead of archive_command or archive_library as the main WAL backup method, it is strongly recommended to use replication slots. Otherwise, the server is free to recycle or remove write-ahead log files before they are backed up, because it does not have any information, either from archive_command or archive_library or the replication slots, about how far the WAL stream has been archived. Note, however, that a replication slot will fill up the server's disk space if the receiver does not keep up with fetching the WAL data. pg_receivewal will preserve group permissions on the received WAL files if group permissions are enabled on the source cluster. EXAMPLES To stream the write-ahead log from the server at mydbserver and store it in the local directory /usr/local/pgsql/archive: $ pg_receivewal -h mydbserver -D /usr/local/pgsql/archive SEE ALSO pg_basebackup(1) PostgreSQL 18.6 2026 PG_RECEIVEWAL(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | ENVIRONMENT | NOTES | EXAMPLES | SEE ALSO
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