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Subject[patch 7/7] Add documentation for extended crashkernel syntax
This adds the documentation for the extended crashkernel syntax into

Signed-off-by: Bernhard Walle <>

Documentation/kdump/kdump.txt | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
--- a/Documentation/kdump/kdump.txt
+++ b/Documentation/kdump/kdump.txt
@@ -231,6 +231,32 @@ Dump-capture kernel config options (Arch
any space below the alignment point will be wasted.

+Extended crashkernel syntax
+While the "crashkernel=size[@offset]" syntax is sufficient for most
+configurations, sometimes it's handy to have the reserved memory dependent
+on the value of System RAM -- that's mostly for distributors that pre-setup
+the kernel command line to avoid a unbootable system after some memory has
+been removed from the machine.
+The syntax is:
+ crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
+ range=start-[end]
+For example:
+ crashkernel=512M-2G:64M,2G-:128M
+This would mean:
+ 1) if the RAM is smaller than 512M, then don't reserve anything
+ (this is the "rescue" case)
+ 2) if the RAM size is between 512M and 2G, then reserve 64M
+ 3) if the RAM size is larger than 2G, then reserve 128M
Boot into System Kernel

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