[Patch v5 5/6] kexec-kdump-howto.txt: renew the path section

[Baoquan He]

In case no target is specified explicitly in /etc/kdump.conf, the behavior
of path is changed, a check need be taken to see if any separate file
system is mounted on any tier of 'path', and also to take the relevant
action. Now the path section need be renewed accordingly.

Signed-off-by: Baoquan He <bhe at redhat.com>
---
 kexec-kdump-howto.txt | 50 +++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 39 insertions(+), 11 deletions(-)

diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt
index 7ffeab9..5582e40 100644
--- a/kexec-kdump-howto.txt
+++ b/kexec-kdump-howto.txt
@@ -364,18 +364,46 @@ to send over the necessary ssh key file. Restart the kdump service via
 '/sbin/systemctl restart kdump.service' to commit this change to your kdump initrd.
 
 Path
+====
+"path" represents the file system path in which vmcore will be saved. In
+fact kdump creates a directory $hostip-$date with-in "path" and saves
+vmcore there. So practically dump is saved in $path/$hostip-$date/. To
+simplify discussion further, if we say dump will be saved in $path, it
+is implied that kdump will create another directory inside path and
+save vmcore there.
+
+If a dump target is specified in kdump.conf, then "path" is relative to the
+specified dump target. For example, if dump target is "ext4 /dev/sda", then
+dump will be saved in "$path" directory on /dev/sda.
+
+Same is the case for nfs dump. If user specified "nfs foo.com:/export/tmp/"
+as dump target, then dump will effectively be saved in
+"foo.com:/export/tmp/var/crash/" directory.
+
+Interpretation of path changes a bit if user has not specified a dump
+target explicitly in kdump.conf. In this case, "path" represents the
+absolute path from root. And dump target and adjusted path are arrived
+at automatically depending on what's mounted in the current system.
+
+Following are few examples.
+
+path /var/crash/
+----------------
+Assuming there is no disk mounted on /var/ or on /var/crash, dump will
+be saved on disk backing rootfs in directory /var/crash.
+
+path /var/crash/ (A separate disk mounted on /var)
+--------------------------------------------------
+Say a disk /dev/sdb is mouted on /var. In this case dump target will
+become /dev/sdb and path will become "/crash" and dump will be saved
+on "sdb:/crash/" directory.
+
+path /var/crash/ (NFS mounted on /var)
+-------------------------------------
+Say foo.com:/export/tmp is mounted on /var. In this case dump target is
+nfs server and path will be adjusted to "/crash" and dump will be saved to
+foo.com:/export/tmp/crash/ directory.
 
-By default, local file system vmcore files are written to /var/crash/%DATE
-on the local system, ssh/scp dumps to /var/crash/%HOST-%DATE on the target
-system, dedicated file system partition dumps to ./var/crash/%DATE, and
-NFS dumps to ./var/crash/%HOST-%DATE, the latter two both relative to
-their respective mount points within the kdump initrd (usually /mnt). The
-'/var/crash' portion of the path can be overridden using kdump.conf's 'path'
-variable, should you wish to write the vmcore out to a different location. For
-example, 'path /data/coredumps' would lead to vmcore files being written to
-/data/coredumps/%DATE if you were dumping to your local file system.  Note
-that the path option is ingnored if your kdump configuration results in the
-core being saved from the initscripts in the root filesystem.
 
 Kdump Post-Capture Executable
 
-- 
1.8.5.3