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.
This commit is contained in:
Robert Watson 2007-12-26 12:56:46 +00:00
parent 35785f6be9
commit 21c0c8925b
Notes: svn2git 2020-12-08 03:00:23 +00:00
svn path=/head/; revision=31159

View file

@ -53,14 +53,16 @@
<quote>swap device</quote> is synonymous with a <quote>swap
partition.</quote></para></note>
<para>To be able to extract a usable core, it is required that at
least one swap partition be large enough to hold all of the bits
in physical memory. When a kernel panics, before the system
reboots, the kernel is smart enough to check to see if a swap
device has been configured as a dump device. If there is a
valid dump device, the kernel dumps the contents of what is in
physical memory to the swap device.</para>
<para>Several types of kernel crash dumps are available: full memory
dumps, which hold the complete contents of physical memory,
minidumps, which hold only memory pages in use by the kernel
(&os;&nbsp; 6.2 and higher), and textdumps, which hold captured
scripted or interactive debugger output (&os;&nbsp;8.0 and higher).
Minidumps are the default dump type as of &os;&nbsp;7.0, and in most
cases will capture all necessary information present in a full
memory dump, as most problems can be isolated only using kernel
state.</para>
<sect2 id="config-dumpdev">
<title>Configuring the Dump Device</title>
@ -72,7 +74,10 @@
has been configured with &man.swapon.8;. This is normally
handled by setting the <varname>dumpdev</varname> variable in
&man.rc.conf.5; to the path of the swap device (the
recommended way to extract a kernel dump).</para>
recommended way to extract a kernel dump) or
<filename>AUTO</filename> to use the first configured swap
device. <filename>AUTO</filename> is the default as of
&os;&nbsp;6.0.</para>
<para>Alternatively, the dump device can be hard-coded via the
<literal>dump</literal> clause in the &man.config.5; line of
@ -140,10 +145,6 @@
space for the dump. Also, do not forget to specify the correct path to your swap
device as it is likely different than
<filename>/dev/ad0s1b</filename>!</para></tip>
<para>The recommended, and certainly the easiest way to automate
obtaining crash dumps is to use the <varname>dumpdev</varname>
variable in &man.rc.conf.5;.</para>
</sect2>
</sect1>