core_collector doc basic fix

Update core_collector in kdump.conf[.5]:
1. accept <command> not limited to makedumpfile
2. add notes about default core_collector
3. add notes about flattened vmcore

Signed-off-by: Dave Young <dyoung@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

kdump.conf

@@ -34,14 +34,22 @@
 #			  dumping to.  Ignored for raw device dumps.
 #		 	  If unset, will default to /var/crash.
 #
-# core_collector makedumpfile <options>
+# core_collector <command> <options>
-#			- This directive allows you to use the dump filtering
+#			- This allows you to specify the command to copy
-#			  program makedumpfile to retrieve your core, which on
+#			  the vmcore.  You could use the dump filtering
-#			  some arches can drastically reduce core file size.
+#			  program makedumpfile, the default one, to retrieve
-#			  See /sbin/makedumpfile --help for a list of options.
+#			  your core, which on some arches can drastically
-#			  Note that the -i and -g options are not needed here,
+#			  reduce core file size. See /sbin/makedumpfile --help
-#			  as the initrd will automatically be populated with
+#			  for a list of options. Note that the -i and -g
-#			  a config file appropriate for the running kernel.
+#			  options are not needed here, as the initrd will
+#			  automatically be populated with a config file
+#			  appropriate for the running kernel.
+#			  Default core_collector for raw dump is:
+#			  "makedumpfile -F -c --message-level 1 -d 31".
+#			  Default core_collector for other targets is:
+#			  "makedumpfile -c --message-level 1 -d 31".
+#			  For core_collector format details please refer to
+#			  kexec-kdump-howto.txt or kdump.conf manpage.
 #
 # extra_bins <binaries | shell scripts>
 # 			- This directive allows you to specify additional
@@ -82,7 +90,7 @@
 #net user@my.server.com
 #sshkey /root/.ssh/kdump_id_rsa
 path /var/crash
-#core_collector makedumpfile -c
+#core_collector makedumpfile -c --message-level 1 -d 31
 #extra_bins /usr/bin/lftp
 #extra_modules gfs2
 #default shell

kdump.conf.5

@@ -61,14 +61,32 @@ Append path to the filesystem device which you are dumping to.
 Ignored for raw device dumps.  If unset, will default to /var/crash.
 .RE
 
-.B core_collector makedumpfile <options> 
+.B core_collector <command> <options>
 .RS
-This directive allows you to use the dump filtering program
+This allows you to specify the command to copy the vmcore.
-makedumpfile to retrieve your core, which on some arches can
+You could use the dump filtering program makedumpfile, the default one,
-drastically reduce core file size.  See /sbin/makedumpfile --help for
+to retrieve your core, which on some arches can drastically reduce
-a list of options.  Note that the -i and -g options are not needed
+core file size.  See /sbin/makedumpfile --help for a list of options.
-here, as the initrd will automatically be populated with a config file
+Note that the -i and -g options are not needed here, as the initrd
-appropriate for the running kernel.
+will automatically be populated with a config file appropriate
+for the running kernel.
+.PP
+Note 1: About default core collector:
+Default core_collector for raw dump is:
+"makedumpfile -F -c --message-level 1 -d 31".
+Default core_collector for other targets is:
+"makedumpfile -c --message-level 1 -d 31".
+Even if core_collector option is commented out in kdump.conf, makedumpfile
+is default core collector and kdump uses it internally.
+If one does not want makedumpfile as default core_collector, then they
+need to specify one using core_collector option to change the behavior.
+.PP
+Note 2: If "makedumpfile -F" is used then you will get a flattened format
+vmcore.flat, you will need to use "makedumpfile -R" to rearrange the
+dump data from stdard input to a normal dumpfile (readable with analysis
+tools).
+ie. "makedumpfile -R vmcore < vmcore.flat"
+
 .RE
 
 .B extra_bins <binaries | shell scripts>
@@ -103,8 +121,48 @@ Note: kdump uses bash as the default shell.
 .RE
 
 .SH EXAMPLES
+Here is some examples for core_collector option:
+.PP
+Core collector command format depends on dump target type. Typically for
+filesystem (local/remote), core_collector should accept two arguments.
+First one is source file and second one is target file. For ex.
+.TP
+ex1.
+core_collector "cp --sparse=always"
 
-see 
+Above will effectively be translated to:
+
+cp --sparse=always /proc/vmcore <dest-path>/vmcore
+.TP
+ex2.
+core_collector "makedumpfile -c --message-level 1 -d 31"
+
+Above will effectively be translated to:
+
+makedumpfile -c --message-level 1 -d 31 /proc/vmcore <dest-path>/vmcore
+.PP
+For dump targets like raw, in general, core collector should expect
+one argument (source file) and should output the processed core on standard
+output. This standard output will be saved to destination using appropriate
+commands.
+
+raw dumps examples:
+.TP
+ex3.
+core_collector "cat"
+
+Above will effectively be translated to.
+
+cat /proc/vmcore | dd of=<target-device>
+.TP
+ex4.
+core_collector "makedumpfile -F -c --message-level 1 -d 31"
+
+Above will effectively be translated to.
+
+makedumpfile -F -c --message-level 1 -d 31 | dd of=<target-device>
+.PP
+examples for other options please see
 .I /etc/kdump.conf
 
 .SH SEE ALSO

kexec-kdump-howto.txt

@@ -440,18 +440,74 @@ is a dump filtering and compression utility provided with kexec-tools. On
 some architectures, it can drastically reduce the size of your vmcore files,
 which becomes very useful on systems with large amounts of memory.
 
-A typical setup is 'core_collector makedumpfile -c', but check the output of
+A typical setup is 'core_collector makedumpfile -F -c --message-level 1 -d 31',
-'/sbin/makedumpfile --help' for a list of all available options (-i and -g
+but check the output of '/sbin/makedumpfile --help' for a list of all available
-don't need to be specified, they're automatically taken care of). Note that
+options (-i and -g don't need to be specified, they're automatically taken care
-use of makedumpfile requires that the kernel-debuginfo package corresponding
+of). Note that use of makedumpfile requires that the kernel-debuginfo package
-with your running kernel be installed.
+corresponding with your running kernel be installed.
 
-Also note that makedumpfile is only used from the initramfs.  Saving a
+Core collector command format depends on dump target type. Typically for
-core from the initscript in the root filesystem is considered a last ditch
+filesystem (local/remote), core_collector should accept two arguments.
-effort, only used when the initramfs has failed to save the core properly.
+First one is source file and second one is target file. For ex.
-As such only the cp utiltiy is used in the initscripts.  The implication
+
-here is that in order to use makedumpfile as your core collector, you must
+ex1.
-specify a dump target in /etc/kdump.conf.
+---
+core_collector "cp --sparse=always"
+
+Above will effectively be translated to:
+
+cp --sparse=always /proc/vmcore <dest-path>/vmcore
+
+ex2.
+---
+core_collector "makedumpfile -c --message-level 1 -d 31"
+
+Above will effectively be translated to:
+
+makedumpfile -c --message-level 1 -d 31 /proc/vmcore <dest-path>/vmcore
+
+
+For dump targets like raw, in general, core collector should expect
+one argument (source file) and should output the processed core on standard
+output. This standard output will be saved to destination using appropriate
+commands.
+
+raw dumps core_collector examples:
+---------
+ex3.
+---
+core_collector "cat"
+
+Above will effectively be translated to.
+
+cat /proc/vmcore | dd of=<target-device>
+
+ex4.
+---
+core_collector "makedumpfile -F -c --message-level 1 -d 31"
+
+Above will effectively be translated to.
+
+makedumpfile -F -c --message-level 1 -d 31 | dd of=<target-device>
+
+About default core collector
+----------------------------
+Default core_collector for ssh/raw dump is:
+"makedumpfile -F -c --message-level 1 -d 31".
+Default core_collector for other targets is:
+"makedumpfile -c --message-level 1 -d 31".
+
+Even if core_collector option is commented out in kdump.conf, makedumpfile
+is default core collector and kdump uses it internally.
+
+If one does not want makedumpfile as default core_collector, then they
+need to specify one using core_collector option to change the behavior.
+
+Note: If "makedumpfile -F" is used then you will get a flattened format
+vmcore.flat, you will need to use "makedumpfile -R" to rearrange the
+dump data from stdard input to a normal dumpfile (readable with analysis
+tools).
+For example: "makedumpfile -R vmcore < vmcore.flat"
 
 Caveats: