Compressed Dump

Compressed Dump White Paper, Version 1.3
page 4
When savecrash runs during boot-up, the dump is copied into the filesystem. savecrash will run faster
when copying compressed dump since the dump size will be smaller compared to uncompressed dump.
savecrash option -p can be used to avoid saving portions of the dump that are sitting in dedicated dump
devices. savecrash option -z is ignored since the dump is already compressed. Giving a chunksize lesser
than the size of memory that belongs to one compression unit for compressed dump, will also be ignored.
The dump can be analyzed using the kernel dump debug tools q4, adb and kwdb, linked with the latest lib-
crash. To use older tools, the dump can be converted into any of the older formats using crashutil.
$ crashutil -v CRASHDIR /var/adm/crash/crash.0 /var/adm/crash/crash.1
will create crash.1 in CRASHDIR format, from crash.0 which is in PARDIR format. crash.1 can then be
used for debugging with older q4, adb or kwdb.
Versions of tools supporting the new dump format are as shown in the table below.
4. Manpages
Table 1: Tool versions supporting the new dump format
Tool Version
q4 B.11.22l (printed on startup)
adb 11.23.01 (output of $B com-
mand in adb)
kwdb 2.1.5 (printed on startup)
Table 2: Manpages changed
Man page Comments
crashconf(1M) &
crashconf(2)
Options to turn compression ON/OFF
savecrash(1M) -s and -z options ignored for the newer dumps
crashutil(1M) conversion to older formats
libcrash(5) Performance optimizations for reading compressed
dumps.