Mention full memor dumps, minidumps, and textdumps in the introduction
to kernel debugging, with consequences for debugging. Mention that the default in more recent FreeBSD versions is to automatically select a swap partition and use it as a dump partition, and don't suggest changing the default. This chapter could use rather serious updating.
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@ -53,14 +53,16 @@
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<quote>swap device</quote> is synonymous with a <quote>swap
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partition.</quote></para></note>
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<para>To be able to extract a usable core, it is required that at
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least one swap partition be large enough to hold all of the bits
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in physical memory. When a kernel panics, before the system
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reboots, the kernel is smart enough to check to see if a swap
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device has been configured as a dump device. If there is a
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valid dump device, the kernel dumps the contents of what is in
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physical memory to the swap device.</para>
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<para>Several types of kernel crash dumps are available: full memory
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dumps, which hold the complete contents of physical memory,
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minidumps, which hold only memory pages in use by the kernel
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(&os; 6.2 and higher), and textdumps, which hold captured
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scripted or interactive debugger output (&os; 8.0 and higher).
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Minidumps are the default dump type as of &os; 7.0, and in most
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cases will capture all necessary information present in a full
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memory dump, as most problems can be isolated only using kernel
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state.</para>
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<sect2 id="config-dumpdev">
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<title>Configuring the Dump Device</title>
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has been configured with &man.swapon.8;. This is normally
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handled by setting the <varname>dumpdev</varname> variable in
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&man.rc.conf.5; to the path of the swap device (the
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recommended way to extract a kernel dump).</para>
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recommended way to extract a kernel dump) or
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<filename>AUTO</filename> to use the first configured swap
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device. <filename>AUTO</filename> is the default as of
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&os; 6.0.</para>
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<para>Alternatively, the dump device can be hard-coded via the
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<literal>dump</literal> clause in the &man.config.5; line of
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@ -140,10 +145,6 @@
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space for the dump. Also, do not forget to specify the correct path to your swap
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device as it is likely different than
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<filename>/dev/ad0s1b</filename>!</para></tip>
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<para>The recommended, and certainly the easiest way to automate
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obtaining crash dumps is to use the <varname>dumpdev</varname>
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variable in &man.rc.conf.5;.</para>
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</sect2>
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</sect1>
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