Add '-u' switch that would uncompress cores that were compressed by

kernel during dump time.

A real life scenario is that cores are compressed to reduce
size of dumpon partition, but we either don't care about space
in the /var/crash or we have a filesystem level compression of
/var/crash. And we want cores to be uncompressed in /var/crash
because we'd like to instantily read them with kgdb. In this
case we want kernel to write cores compressed, but savecore(1)
write them uncompressed.

Reviewed by:	markj, gallatin
Relnotes:	yes
Differential Revision:	https://reviews.freebsd.org/D27245

1 files changed, 4 insertions, 2 deletions

diff --git a/sbin/savecore/savecore.8 b/sbin/savecore/savecore.8
index e7b0414b62dc..512da5cc3dae 100644
--- a/sbin/savecore/savecore.8
+++ b/sbin/savecore/savecore.8
@@ -28,7 +28,7 @@
 .\"     From: @(#)savecore.8	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD$
 .\"
-.Dd March 17, 2018
+.Dd November 17, 2020
 .Dt SAVECORE 8
 .Os
 .Sh NAME
@@ -45,7 +45,7 @@
 .Op Ar device ...
 .Nm
 .Op Fl -libxo
-.Op Fl fkvz
+.Op Fl fkuvz
 .Op Fl m Ar maxdumps
 .Op Ar directory Op Ar device ...
 .Sh DESCRIPTION
@@ -92,6 +92,8 @@ Once the number of stored dumps is equal to
 .Ar maxdumps
 the counter will restart from
 .Dv 0 .
+.It Fl u
+Uncompress the dump in case it was compressed by the kernel.
 .It Fl v
 Print out some additional debugging information.
 Specify twice for more information.