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* docs/logging.html[.in] qemud/libvirtd.conf qemud/qemud.c src/logging.[ch]: cleanup the logging code and docs to remove all references to log level 0, cleanup hardcoded values and add a default VIR_LOG_DEFAULT value, patch by Amy Griffis daniel
199 lines
11 KiB
HTML
199 lines
11 KiB
HTML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<!--
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This file is autogenerated from logging.html.in
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Do not edit this file. Changes will be lost.
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-->
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
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<link rel="stylesheet" type="text/css" href="main.css" />
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<link rel="SHORTCUT ICON" href="32favicon.png" />
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<title>libvirt: Logging in the library and the daemon</title>
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<meta name="description" content="libvirt, virtualization, virtualization API" />
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</head>
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<body>
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<div id="header">
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<div id="headerLogo"></div>
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<div id="headerSearch">
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<form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><div>
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<input id="query" name="query" type="text" size="12" value="" />
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<input id="submit" name="submit" type="submit" value="Search" />
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</div></form>
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</div>
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</div>
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<div id="body">
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<div id="menu">
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<ul class="l0"><li>
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<div>
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<a title="Front page of the libvirt website" class="inactive" href="index.html">Home</a>
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</div>
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</li><li>
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<div>
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<a title="Details of new features and bugs fixed in each release" class="inactive" href="news.html">News</a>
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</div>
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</li><li>
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<div>
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<a title="Get the latest source releases, binary builds and get access to the source repository" class="inactive" href="downloads.html">Downloads</a>
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</div>
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</li><li>
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<div>
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<a title="Information for users, administrators and developers" class="active" href="docs.html">Documentation</a>
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<ul class="l1"><li>
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<div>
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<a title="Information about deploying and using libvirt" class="active" href="deployment.html">Deployment</a>
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<ul class="l2"><li>
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<div>
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<a title="The URI formats used for connecting to libvirt" class="inactive" href="uri.html">URI format</a>
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</div>
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</li><li>
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<div>
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<a title="Enable remote access over TCP" class="inactive" href="remote.html">Remote access</a>
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</li><li>
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<div>
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<a title="Configure authentication for the libvirt daemon" class="inactive" href="auth.html">Authentication</a>
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</div>
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</li><li>
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<div>
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<a title="Access the libvirt daemon from a native Windows client" class="inactive" href="windows.html">Windows port</a>
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</div>
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</li><li>
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<div>
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<span class="active">Logging</span>
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</div>
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</li></ul>
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</div>
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</li><li>
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<div>
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<a title="Overview of the logical subsystems in the libvirt API" class="inactive" href="intro.html">Architecture</a>
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</div>
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</li><li>
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<div>
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<a title="Description of the XML formats used in libvirt" class="inactive" href="format.html">XML format</a>
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</div>
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</li><li>
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<div>
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<a title="Hypervisor specific driver information" class="inactive" href="drivers.html">Drivers</a>
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</div>
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</li><li>
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<div>
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<a title="Reference manual for the C public API" class="inactive" href="html/index.html">API reference</a>
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</div>
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</li><li>
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<div>
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<a title="Bindings of the libvirt API for other languages" class="inactive" href="bindings.html">Language bindings</a>
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</div>
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</li><li>
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<div>
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<a title="Working on the internals of libvirt API, driver and daemon code" class="inactive" href="internals.html">Internals</a>
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</div>
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</li></ul>
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</div>
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</li><li>
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<div>
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<a title="User contributed content" class="inactive" href="http://wiki.libvirt.org">Wiki</a>
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</div>
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</li><li>
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<div>
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<a title="Frequently asked questions" class="inactive" href="FAQ.html">FAQ</a>
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</div>
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</li><li>
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<div>
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<a title="How and where to report bugs and request features" class="inactive" href="bugs.html">Bug reports</a>
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</li><li>
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<div>
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<a title="How to contact the developers via email and IRC" class="inactive" href="contact.html">Contact</a>
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</div>
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</li><li>
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<div>
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<a title="Miscellaneous links of interest related to libvirt" class="inactive" href="relatedlinks.html">Related Links</a>
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</li><li>
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<div>
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<a title="Overview of all content on the website" class="inactive" href="sitemap.html">Sitemap</a>
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</div>
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</li></ul>
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</div>
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<div id="content">
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<h1>Logging in the library and the daemon</h1>
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<p>Libvirt includes logging facilities starting from version 0.6.0,
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this complements the <a href="errors.html">error handling</a>
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mechanism and APIs to allow tracing though the execution of the
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library as well as in the libvirtd daemon.</p>
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<p>The logging functionalities in libvirt are based on 3 key concepts,
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similar to the one present in other generic logging facilities like
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log4j:</p>
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<ul><li>log messages: they are information generated at runtime by
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the libvirt code, it includes a priority level (DEBUG = 1,
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INFO = 2, WARNING = 3, ERROR = 4), a category, function name and
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line number, indicating where it originated from, and finally
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a formatted message, in addition the library adds a timestamp
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at the begining of the message</li><li>log filters: it's a set of patter and priorities allowing to acept
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or reject a log message, if the message category matches a filter,
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the message priority is compared to the filter priority, if lower
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the message is discarded, if higher the message is output. If
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no filter matches, then a general priority level is applied to
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all remaining messages. This allows to capture for example all
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debug messages for the QEmu driver, but otherwise only allow
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errors to show up from other parts</li><li>log outputs: once a message has gone though filtering a set of
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output defines where to send the message, they can also filter
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based on the priority, for example it may be useful to output
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all messages to a debugging file but only allow errors to be
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logged though syslog.</li></ul>
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<p>The library configuration of logging is though 3 environment variables
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allowing to control the logging behaviour:</p>
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<ul><li>LIBVIRT_DEBUG: it can take the four following values:
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<ul><li>1 or "debug": asking the library to log every message emitted,
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though the filters can be used to avoid filling up the output</li><li>2 or "info": log all non-debugging informations</li><li>3 or "warn": log warnings and errors, that's the default value</li><li>4 or "error": log only error messages</li></ul></li><li>LIBVIRT_LOG_FILTERS: allow to define logging filters</li><li>LIBVIRT_LOG_OUTPUTS: allow to define logging outputs</li></ul>
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<p>Similary the daemon logging behaviour can be tuned using 3 config
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variables, stored in the configuration file:
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</p>
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<ul><li>log_level: accepts the following values:
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<ul><li>4: only errors</li><li>3: warnings and errors</li><li>2: informations, warnings and errors</li><li>1: debug and everything</li></ul></li><li>log_filters: allow to define logging filters</li><li>log_outputs: allow to define logging outputs</li></ul>
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<p>In both case the syntax for filters and outputs is similar.</p>
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<p>The format for a filter is:</p>
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<pre>x:name</pre>
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<p>where <code>name</code> is a match string e.g. <code>remote</code> or
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<code>qemu</code> and the x is the minimal level where matching messages
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should be logged:</p>
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<ul><li>1: DEBUG</li><li>2: INFO</li><li>3: WARNING</li><li>4: ERROR</li></ul>
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<p>Multiple filter can be defined in a single string, they just need to be
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separated by spaces, e.g: <code>"3:remote 4:event"</code> to only get
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warning or errors from the remote layer and only errors from the event
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layer.</p>
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<p>
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</p>
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<p>The format for an output can be one of those 3 forms:</p>
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<ul><li><code>x:stderr</code> output goes to stderr</li><li><code>x:syslog:name</code> use syslog for the output and use the
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given <code>name</code> as the ident</li><li><code>x:file:file_path</code>output to a file, with the given
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filepath</li></ul>
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<p>In all cases the x prefix is the minimal level, acting as a filter:</p>
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<ul><li>1: DEBUG</li><li>2: INFO</li><li>3: WARNING</li><li>4: ERROR</li></ul>
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<p>Multiple output can be defined , they just need to be separated by
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spaces, e.g.: <code>"3:syslog:libvirtd 1:file:/tmp/libvirt.log"</code>
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will log all warnings and errors to syslog under the libvirtd ident
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but also log everything debugging and informations included in the
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file <code>/tmp/libvirt.log</code></p>
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<p>For example setting up the following:</p>
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<pre>export LIBVIRT_DEBUG=1
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export LIBVIRT_LOG_OUTPUTS="1:file:virsh.log"</pre>
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<p>and then running virsh will accumulate the logs in the
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<code>virsh.log</code> file in a way similar to:</p>
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<pre>14:29:04.771: debug : virInitialize:278 : register drivers
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14:29:04.771: debug : virRegisterDriver:618 : registering Test as driver 0</pre>
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<p>the messages are timestamped, there is also the level recorded,
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if debug the name of the function is also printed and then the formatted
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message. This should be sufficient to at least get a precise idea of
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what is happening and where things are going wrong, allowing to then
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put the correct breakpoints when running under a debugger.</p>
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</div>
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Sponsored by:<br /><a href="http://et.redhat.com/"><img src="et.png" alt="Project sponsored by Red Hat Emerging Technology" /></a></p>
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