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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>pg_checksums</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="pgarchivecleanup.html" title="pg_archivecleanup" /><link rel="next" href="app-pgcontroldata.html" title="pg_controldata" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center"><span class="application">pg_checksums</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgarchivecleanup.html" title="pg_archivecleanup">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><th width="60%" align="center">PostgreSQL Server Applications</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="app-pgcontroldata.html" title="pg_controldata">Next</a></td></tr></table><hr /></div><div class="refentry" id="APP-PGCHECKSUMS"><div class="titlepage"></div><a id="id-1.9.5.5.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle"><span class="application">pg_checksums</span></span></h2><p>pg_checksums — enable, disable or check data checksums in a <span class="productname">PostgreSQL</span> database cluster</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p id="id-1.9.5.5.4.1"><code class="command">pg_checksums</code> [<em class="replaceable"><code>option</code></em>...] [[ <code class="option">-D</code> | <code class="option">--pgdata</code> ]<em class="replaceable"><code>datadir</code></em>]</p></div></div><div class="refsect1" id="R1-APP-PG_CHECKSUMS-1"><h2>Description</h2><p>
<span class="application">pg_checksums</span> checks, enables or disables data
checksums in a <span class="productname">PostgreSQL</span> cluster. The server
must be shut down cleanly before running
<span class="application">pg_checksums</span>. When verifying checksums, the exit
status is zero if there are no checksum errors, and nonzero if at least one
checksum failure is detected. When enabling or disabling checksums, the
exit status is nonzero if the operation failed.
</p><p>
When verifying checksums, every file in the cluster is scanned. When
enabling checksums, each relation file block with a changed checksum is
rewritten in-place.
Disabling checksums only updates the file <code class="filename">pg_control</code>.
</p></div><div class="refsect1" id="id-1.9.5.5.6"><h2>Options</h2><p>
The following command-line options are available:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-D <em class="replaceable"><code>directory</code></em></code><br /></span><span class="term"><code class="option">--pgdata=<em class="replaceable"><code>directory</code></em></code></span></dt><dd><p>
Specifies the directory where the database cluster is stored.
</p></dd><dt><span class="term"><code class="option">-c</code><br /></span><span class="term"><code class="option">--check</code></span></dt><dd><p>
Checks checksums. This is the default mode if nothing else is
specified.
</p></dd><dt><span class="term"><code class="option">-d</code><br /></span><span class="term"><code class="option">--disable</code></span></dt><dd><p>
Disables checksums.
</p></dd><dt><span class="term"><code class="option">-e</code><br /></span><span class="term"><code class="option">--enable</code></span></dt><dd><p>
Enables checksums.
</p></dd><dt><span class="term"><code class="option">-f <em class="replaceable"><code>filenode</code></em></code><br /></span><span class="term"><code class="option">--filenode=<em class="replaceable"><code>filenode</code></em></code></span></dt><dd><p>
Only validate checksums in the relation with filenode
<em class="replaceable"><code>filenode</code></em>.
</p></dd><dt><span class="term"><code class="option">-N</code><br /></span><span class="term"><code class="option">--no-sync</code></span></dt><dd><p>
By default, <code class="command">pg_checksums</code> will wait for all files
to be written safely to disk. This option causes
<code class="command">pg_checksums</code> to return without waiting, which is
faster, but means that a subsequent operating system crash can leave
the updated data directory corrupt. Generally, this option is useful
for testing but should not be used on a production installation.
This option has no effect when using <code class="literal">--check</code>.
</p></dd><dt><span class="term"><code class="option">-P</code><br /></span><span class="term"><code class="option">--progress</code></span></dt><dd><p>
Enable progress reporting. Turning this on will deliver a progress
report while checking or enabling checksums.
</p></dd><dt><span class="term"><code class="option">-v</code><br /></span><span class="term"><code class="option">--verbose</code></span></dt><dd><p>
Enable verbose output. Lists all checked files.
</p></dd><dt><span class="term"><code class="option">-V</code><br /></span><span class="term"><code class="option">--version</code></span></dt><dd><p>
Print the <span class="application">pg_checksums</span> version and exit.
</p></dd><dt><span class="term"><code class="option">-?</code><br /></span><span class="term"><code class="option">--help</code></span></dt><dd><p>
Show help about <span class="application">pg_checksums</span> command line
arguments, and exit.
</p></dd></dl></div><p>
</p></div><div class="refsect1" id="id-1.9.5.5.7"><h2>Environment</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">PGDATA</code></span></dt><dd><p>
Specifies the directory where the database cluster is
stored; can be overridden using the <code class="option">-D</code> option.
</p></dd><dt><span class="term"><code class="envar">PG_COLOR</code></span></dt><dd><p>
Specifies whether to use color in diagnostic messages. Possible values
are <code class="literal">always</code>, <code class="literal">auto</code> and
<code class="literal">never</code>.
</p></dd></dl></div></div><div class="refsect1" id="id-1.9.5.5.8"><h2>Notes</h2><p>
Enabling checksums in a large cluster can potentially take a long time.
During this operation, the cluster or other programs that write to the
data directory must not be started or else data loss may occur.
</p><p>
When using a replication setup with tools which perform direct copies
of relation file blocks (for example <a class="xref" href="app-pgrewind.html" title="pg_rewind"><span class="refentrytitle"><span class="application">pg_rewind</span></span></a>),
enabling or disabling checksums can lead to page corruptions in the
shape of incorrect checksums if the operation is not done consistently
across all nodes. When enabling or disabling checksums in a replication
setup, it is thus recommended to stop all the clusters before switching
them all consistently. Destroying all standbys, performing the operation
on the primary and finally recreating the standbys from scratch is also
safe.
</p><p>
If <span class="application">pg_checksums</span> is aborted or killed while
enabling or disabling checksums, the cluster's data checksum configuration
remains unchanged, and <span class="application">pg_checksums</span> can be
re-run to perform the same operation.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pgarchivecleanup.html" title="pg_archivecleanup">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="app-pgcontroldata.html" title="pg_controldata">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="application">pg_archivecleanup</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="40%" align="right" valign="top"> <span class="application">pg_controldata</span></td></tr></table></div></body></html>
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