[PATCH v6 0/6] Improve kdump debugging messages

[Lianbo Jiang]

Sometimes, debugging the kdump service failure becomes very challenging
because there is no complete debugging information, which requires
modification of the options or the scripts like kdumpctl, mkdumprd, etc
to collect the information for troubleshooting.

That means users have to wait for the next failure so that they can
capture the additional information, which could waste valuable time.

This patch series will improve kdump debugging messages and have a
chance to save them to journald or a file. It includes the following
patches:
[1] [PATCH 1/5] introduce the kdump logger from the dracut
[2] [PATCH 2/5] enable the logger for kdump
[3] [PATCH 3/5] kdump.sysconfig: add the kdump logger configurations
[4] [PATCH 4/5] kdumpctl: add the '-d' option to enable the kexec loading
    debugging messages
[5] [PATCH 5/5] Improve debugging in the kdump kernel
[6] [PATCH 6/6] Doc: add a documentation for the usage of logger

In addition, this patch series won't cause performance degradation,
basically this effect can be ignored. I simply checked the result of
executing the loading command as follow:

[1] before
# time kdumpctl start
Detected change(s) in the following file(s):
  /etc/kdump.conf
Rebuilding /boot/initramfs-4.18.0-232.el8.x86_64kdump.img
Tips: If early kdump is enabled, also require rebuilding the system initramfs to make the
changes take effect for early kdump.
kexec: loaded kdump kernel
Starting kdump: [OK]

real    0m9.145s
user    0m20.733s
sys     0m1.765s

[2] after
# time kdumpctl start
kdump: Detected change(s) in the following file(s):  /etc/kdump.conf
kdump: Rebuilding /boot/initramfs-4.18.0-232.el8.x86_64kdump.img
kdump: Tips: If early kdump is enabled, also require rebuilding the system initramfs to
make the changes take effect for early kdump.
kdump: kexec: loaded kdump kernel
kdump: Starting kdump: [OK]

real    0m9.177s
user    0m20.784s
sys     0m1.901s

Changes since v5:
[1] Only added a documentation for the usage of logger, there's
    no code change.

Note:
Currently, kexec-tools disable storing logs to journald in order
to save memory, please refer to the following changes:
+++ b/dracut-module-setup.sh
@@ -788,6 +788,8 @@ kdump_install_random_seed() {
 }
...
 kdump_install_systemd_conf() {
     if ! is_fadump_capable && [ "$failure_action" != "shell"
]; then
         mkdir -p ${initdir}/etc/systemd/journald.conf.d
         echo "[Journal]" >
${initdir}/etc/systemd/journald.conf.d/kdump.conf
         echo "Storage=none" >>
${initdir}/etc/systemd/journald.conf.d/kdump.conf
                       ^^^^
If we want to use the journald in kdump kernel, we have to change it to
"Storage=auto" or "volatile".

Lianbo Jiang (6):
  introduce the kdump logger from the dracut
  enable the logger for kdump
  kdump.sysconfig: add the kdump logger configurations
  kdumpctl: add the '-d' option to enable the kexec loading debugging
    messages
  Improve debugging in the kdump kernel
  Doc: add a documentation for the usage of logger

 dracut-early-kdump-module-setup.sh |   3 +
 dracut-early-kdump.sh              |  24 +-
 dracut-kdump.sh                    |  68 +++---
 dracut-module-setup.sh             |   4 +
 kdump-lib-initramfs.sh             |  67 ++++--
 kdump-lib.sh                       |  23 +-
 kdump-logger.sh                    | 344 +++++++++++++++++++++++++++++
 kdump.sysconfig                    |  16 ++
 kdump.sysconfig.aarch64            |  16 ++
 kdump.sysconfig.i386               |  16 ++
 kdump.sysconfig.ppc64              |  16 ++
 kdump.sysconfig.ppc64le            |  16 ++
 kdump.sysconfig.s390x              |  16 ++
 kdump.sysconfig.x86_64             |  16 ++
 kdumpctl                           | 241 +++++++++++---------
 kexec-kdump-howto.txt              |  35 +++
 kexec-tools.spec                   |   2 +
 mkdumprd                           |  12 +-
 18 files changed, 766 insertions(+), 169 deletions(-)
 create mode 100755 kdump-logger.sh

-- 
2.17.1