Support saving crash dumps on systems hosted in RAM

By default, Kdump copies the entire vmcore to the disk and reboots the
system afterwards. While this works in most cases, it does not work for
systems hosted in RAM where the crash dump will be lost once rebooted.
To support this scenario, a new option in the kdump.conf,
save_core_to_ram, is added and commented out. Setting this option to 1
will allow a compressed crash dump to be produced by utilizing the
core_collector option if specified, otherwise the dmesg log will be
extracted from the vmcore. This is especially necessary because there is
no disk to save the dump to, and there is not enough space in the
pre-allocated crashkernel memory space to save an entire vmcore.

Author: nangelastro

SPECS/kexec-tools/kdump.conf

@@ -162,6 +162,18 @@
 #             to send fence_kdump notifications to.
 #             (this option is mandatory to enable fence_kdump).
 #
+# save_core_to_ram <0 | 1>
+#           - By default, the entire vmcore gets copied and the system reboots
+#             after the crash dump is saved. Enabling this option by specifying
+#             1 will instead save a compressed dump and not reboot after the
+#             dump is saved. The core_collector option, if also specified, is
+#             used to determine how the crash dump should be compressed. If the
+#             core_collector option is not set, then only the dmesg log will
+#             be saved.
+#
+#             This option is particularly useful when the operating system is
+#             running in RAM and reboots would otherwise remove the crash dump.
+#
 
 #raw /dev/vg/lv_kdump
 #ext4 /dev/vg/lv_kdump
@@ -183,3 +195,4 @@ core_collector makedumpfile -l --message-level 1 -d 31
 #dracut_args --omit-drivers "cfg80211 snd" --add-drivers "ext2 ext3"
 #fence_kdump_args -p 7410 -f auto -c 0 -i 10
 #fence_kdump_nodes node1 node2
+#save_core_to_ram 0

SPECS/kexec-tools/kdumpctl

@@ -87,6 +87,29 @@ save_core()
 	fi
 }
 
+save_compressed_core()
+{
+	coredir="/var/crash/`date +"%Y-%m-%d-%H:%M"`"
+	mkdir -p "$coredir"
+	CORE_COLLECTOR=`grep ^core_collector $KDUMP_CONFIG_FILE | cut -d\  -f2`
+
+	if [[ -n "$CORE_COLLECTOR" ]]; then
+		# Utilize the core_collector option set in kdump.conf to produce a compressed crash dump.
+		CORE_COLLECTOR=`type -P $CORE_COLLECTOR`
+		$CORE_COLLECTOR /proc/vmcore "$coredir/vmcore"
+		if [ $? != 0 ]; then
+			echo "failed to collect vmcore with $CORE_COLLECTOR to $coredir" >&2
+		fi
+	else
+		# Resort to extracting the dmesg log from vmcore instead of compressing and filtering the vmcore.
+		# This should produce the minimum-sized output that can reliably fit in memory.
+		makedumpfile --dump-dmesg "$coredir/vmcore" "$coredir/dmesg" >/dev/null 2>&1
+		if [ $? != 0 ]; then
+			echo "failed to extract dmesg from vmcore to $coredir" >&2
+		fi
+	fi
+}
+
 rebuild_fadump_initrd()
 {
 	local target_initrd_tmp
@@ -243,7 +266,7 @@ check_config()
 		case "$config_opt" in
 		\#* | "")
 			;;
-		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|failure_action|default|final_action|force_rebuild|force_no_rebuild|dracut_args|fence_kdump_args|fence_kdump_nodes)
+		raw|ext2|ext3|ext4|minix|btrfs|xfs|nfs|ssh|sshkey|path|core_collector|kdump_post|kdump_pre|extra_bins|extra_modules|failure_action|default|final_action|force_rebuild|force_no_rebuild|dracut_args|fence_kdump_args|fence_kdump_nodes|save_core_to_ram)
 			# remove inline comments after the end of a directive.
 			[ -z "$config_val" ] && {
 				echo "Invalid kdump config value for option $config_opt."
@@ -882,7 +905,7 @@ save_raw()
 		coredir="${kdump_dir}/`date +"%Y-%m-%d-%H:%M"`"
 	fi
 
-	mkdir -p "$coredir"
+	mkdir -p $coredir
 	[ -d "$coredir" ] || {
 		echo "failed to create $coredir"
 		return 1
@@ -1248,6 +1271,23 @@ main ()
 	case "$1" in
 	  start)
 		if [ -s /proc/vmcore ]; then
+			local _save_core_to_ram save_core_to_ram="0"
+			_save_core_to_ram=`grep ^save_core_to_ram $KDUMP_CONFIG_FILE 2>/dev/null`
+
+			if [ $? -eq 0 ]; then
+				save_core_to_ram=`echo $_save_core_to_ram | cut -d' '  -f2`
+
+				if [ "$save_core_to_ram" != "0" ] && [ "$save_core_to_ram" != "1" ]; then
+					echo "Error: save_core_to_ram value is invalid"
+					return 1
+				fi
+			fi
+
+			if [ "$save_core_to_ram" == "1" ]; then
+				save_compressed_core
+				exit 0
+			fi
+
 			save_core
 			reboot
 		else

SPECS/kexec-tools/kexec-tools.signatures.json

@@ -20,14 +20,14 @@
   "kdump-lib-initramfs.sh": "ff4b63f99470ee796fd7e4a532dde241c4da02909306926a08a172457775a92a",
   "kdump-lib.sh": "3d50507626d4a92b8448c7d6604923f6f460c4cb5c8b18977381a7d5e516dfba",
   "kdump-udev-throttler": "125d538a59172f779b40ea32fea1e4eb50d849f25eb2537a48328d4401136679",
-  "kdump.conf": "c4cd6c4a2f00e7df10d939bc2f35f8b6b8a3edd71245aa3ba0d7fff53d9f42e8",
+  "kdump.conf": "2e65b6237560286f74530e104ee6556387b5c08ced883b1bb0a443d1e6d3c0cb",
   "kdump.conf.5": "bab6c7b171f76e8c6df91bb7db852815caacbc3cd3d4309a1dc58d36950440e4",
   "kdump.service": "ed8d22fafa6cfafaddcfd9fec82e3fa7fa42aa0366f69676fafa97e200b0506a",
   "kdump.sysconfig": "d03a24659c08aa4ce5a8e54edbe64e149f8c572c76c4e338d84dbdfbeab8fb63",
   "kdump.sysconfig.aarch64": "a829f3a0f88d983ccec2782b048f12a2eafca71aac4dd42acac2eaea8f7dd8d9",
   "kdump.sysconfig.i386": "1175bcc11be49841d4b8c3f9612e68bb7b2e0e8f00067ffa782fd9dba04f821d",
   "kdump.sysconfig.x86_64": "850b3be780165d0721edb8d34b2ba28aafc60b29850ff627daf04190369e359c",
-  "kdumpctl": "34976fa2ca34a455f393d2ac212a628d73ba4113b44f0e819c3cb5b1195e504b",
+  "kdumpctl": "0672f1df54e36f16188e9a3a1b51dff81fbb03686e9f0669c526d9f80a6294ce",
   "kdumpctl.8": "025a39d212eed0584da7c23c1bb50d6ab797a0fa3c686ac6b80391af875dbaec",
   "kexec-kdump-howto.txt": "e783390a9aa582a2b5e7981cd3277081385340b5873a3f0633c789811876eccb",
   "kexec-tools-2.0.27.tar.xz": "38d78bcfa33a88928324b57dc81f50c1dfc279eede45e80957ca18f4e84b8187",

SPECS/kexec-tools/kexec-tools.spec

@@ -330,6 +330,9 @@ done
 /usr/share/makedumpfile/
 
 %changelog
+* Mon Mar 31 2026 Nicholas Angelastro <nangelastro@microsoft.com> - 2.0.27-9
+- Support saving crash dumps on systems hosted in RAM
+
 * Tue Nov 11 2025 Mayank Singh <mayansingh@microsoft.com> - 2.0.27-8
 - Updated dependency handling for kexec-tools:
   Changed from hard dependency on a single package.