MAKEDUMPFILE(8) Linux System Administrator's Manual MAKEDUMPFILE(8)
NAME
makedumpfile - make a small dumpfile of kdump
SYNOPSIS
makedumpfile [OPTION] [-x VMLINUX|-i VMCOREINFO] VMCORE DUMPFILE
makedumpfile -F [OPTION] [-x VMLINUX|-i VMCOREINFO] VMCORE
makedumpfile [OPTION] -x VMLINUX [--config FILTERCONFIGFILE] [--eppic
EPPICMACRO] VMCORE DUMPFILE
makedumpfile -R DUMPFILE
makedumpfile --split [OPTION] [-x VMLINUX|-i VMCOREINFO] VMCORE DUMP-
FILE1 DUMPFILE2 [DUMPFILE3 ..]
makedumpfile [OPTION] [-x VMLINUX|-i VMCOREINFO] --num-threads THREAD-
NUM VMCORE DUMPFILE
makedumpfile --reassemble DUMPFILE1 DUMPFILE2 [DUMPFILE3 ..] DUMPFILE
makedumpfile -g VMCOREINFO -x VMLINUX
makedumpfile [OPTION] [--xen-syms XEN-SYMS|--xen-vmcoreinfo VMCORE-
INFO] VMCORE DUMPFILE
makedumpfile --dump-dmesg [--partial-dmesg] [-x VMLINUX|-i VMCOREINFO]
VMCORE LOGFILE
makedumpfile [OPTION] -x VMLINUX --diskset=VMCORE1 --diskset=VMCORE2
[--diskset=VMCORE3 ..] DUMPFILE
makedumpfile -h
makedumpfile -v
DESCRIPTION
With kdump, the memory image of the first kernel (called "panicked ker-
nel") can be taken as /proc/vmcore while the second kernel (called
"kdump kernel" or "capture kernel") is running. This document repre-
sents /proc/vmcore as VMCORE. makedumpfile makes a small DUMPFILE by
compressing dump data or by excluding unnecessary pages for analysis,
or both. makedumpfile needs the first kernel's debug information, so
that it can distinguish unnecessary pages by analyzing how the first
kernel uses the memory. The information can be taken from VMLINUX or
VMCOREINFO.
makedumpfile can exclude the following types of pages while copying
VMCORE to DUMPFILE, and a user can choose which type of pages will be
excluded.
- Pages filled with zero
- Cache pages without private flag (non-private cache)
- Cache pages with private flag (private cache)
- User process data pages
- Free pages
makedumpfile provides two DUMPFILE formats (the ELF format and the
kdump-compressed format). By default, makedumpfile makes a DUMPFILE in
the kdump-compressed format. The kdump-compressed format is readable
only with the crash utility, and it can be smaller than the ELF format
because of the compression support. The ELF format is readable with GDB
and the crash utility. If a user wants to use GDB, DUMPFILE format has
to be explicitly specified to be the ELF format.
Apart from the exclusion of unnecessary pages mentioned above, make-
dumpfile allows user to filter out targeted kernel data. The filter
config file can be used to specify kernel/module symbols and its mem-
bers that need to be filtered out through the erase command syntax.
makedumpfile reads the filter config and builds the list of memory
addresses and its sizes after processing filter commands. The memory
locations that require to be filtered out are then poisoned with char-
acter 'X' (58 in Hex). Refer to makedumpfile.conf(5) for file format.
Eppic macros can also be used to specify kernel symbols and its members
that need to be filtered. Eppic provides C semantics including language
constructs such as conditional statements, logical and arithmetic oper-
ators, functions, nested loops to traverse and erase kernel data.
--eppic requires eppic_makedumpfile.so and eppic library. eppic_make-
dumpfile.so can be built from makedumpfile source. Refer to
http://code.google.com/p/eppic/ to build eppic library libeppic.a and
for more information on writing eppic macros.
To analyze the first kernel's memory usage, makedumpfile can refer to
VMCOREINFO instead of VMLINUX. VMCOREINFO contains the first kernel's
information (structure size, field offset, etc.), and VMCOREINFO is
small enough to be included into the second kernel's initrd.
If the second kernel is running on its initrd without mounting a root
file system, makedumpfile cannot refer to VMLINUX because the second
kernel's initrd cannot include a large file like VMLINUX. To solve the
problem, makedumpfile makes VMCOREINFO beforehand, and it refers to
VMCOREINFO instead of VMLINUX while the second kernel is running.
VMCORE has contained VMCOREINFO since linux-2.6.24, and a user does not
need to specify neither -x nor -i option.
If the second kernel is running on its initrd without mounting any file
system, a user needs to transport the dump data to a remote host. To
transport the dump data by SSH, makedumpfile outputs the dump data in
the intermediate format (the flattened format) to the standard output.
By piping the output data to SSH, a user can transport the dump data to
a remote host. Note that analysis tools (crash utility before version
5.1.2 or GDB) cannot read the flattened format directly, so on a remote
host the received data in the flattened format needs to be rearranged
to a readable DUMPFILE format by makedumpfile (or makedumpfile-R.pl).
makedumpfile can read a DUMPFILE in the kdump-compressed format instead
of VMCORE and re-filter it. This feature is useful in situation that
users need to reduce the file size of DUMPFILE for sending it somewhere
by ftp/scp/etc. (If all of the page types, which are specified by a new
dump_level, are excluded from an original DUMPFILE already, a new DUMP-
FILE is the same as an original DUMPFILE.)
For example, makedumpfile can create a DUMPFILE of dump_level 31 from
the one of dump_level 3 like the following:
Example:
# makedumpfile -c -d 3 /proc/vmcore dumpfile.1
# makedumpfile -c -d 31 dumpfile.1 dumpfile.2
makedumpfile can read VMCORE(s) in three kinds of sadump formats: sin-
gle partition format, diskset format and media backup format, and can
convert each of them into kdump-compressed format with filtering and
compression processing. Note that for VMCORE(s) created by sadump, you
always need to pass VMLINUX with -x option. Also, to pass multiple
VMCOREs created on diskset configuration, you need to use --diskset
option.
OPTIONS
-c,-l,-p,-z
Compress dump data by the page using the following compression
library respectively:
-c : zlib
-l : lzo
-p : snappy
-z : zstd
(-l, -p and -z option need USELZO=on, USESNAPPY=on and
USEZSTD=on respectively when building makedumpfile)
A user cannot specify this option with -E option, because the
ELF format does not support compressed data.
Example:
# makedumpfile -c -d 31 -x vmlinux /proc/vmcore dumpfile
-d dump_level
Specify the type of unnecessary page for analysis.
Pages of the specified type are not copied to DUMPFILE. The page
type marked in the following table is excluded. A user can spec-
ify multiple page types by setting the sum of each page type for
dump_level. The maximum of dump_level is 31. Note that a
dump_level for Xen dump filtering is 0 or 1 on a machine other
than x86_64. On a x86_64 machine, even 2 or bigger dump level
will be effective if you specify domain-0's vmlinux with -x
option. Then the pages are excluded only from domain-0.
If specifying multiple dump_levels with the delimiter ',', make-
dumpfile retries to create DUMPFILE using the next dump_level
when the size of a dumpfile exceeds the limit specified with
'-L' or when a "No space on device" error happens. For example,
if dump_level is "11,31" and makedumpfile fails with dump_level
11, makedumpfile retries with dump_level 31.
Example:
# makedumpfile -d 11 -x vmlinux /proc/vmcore dumpfile
# makedumpfile -d 11,31 -x vmlinux /proc/vmcore dumpfile
Base level:
dump_level consists of five bits, so there are five base levels
to specify the type of unnecessary page.
1 : Exclude the pages filled with zero.
2 : Exclude the non-private cache pages.
4 : Exclude all cache pages.
8 : Exclude the user process data pages.
16 : Exclude the free pages.
Here is the all combinations of the bits.
| |non- | | |
dump | zero |private|private| user | free
level | page |cache |cache | data | page
-------+------+-------+-------+------+------
0 | | | | |
1 | X | | | |
2 | | X | | |
3 | X | X | | |
4 | | X | X | |
5 | X | X | X | |
6 | | X | X | |
7 | X | X | X | |
8 | | | | X |
9 | X | | | X |
10 | | X | | X |
11 | X | X | | X |
12 | | X | X | X |
13 | X | X | X | X |
14 | | X | X | X |
15 | X | X | X | X |
16 | | | | | X
17 | X | | | | X
18 | | X | | | X
19 | X | X | | | X
20 | | X | X | | X
21 | X | X | X | | X
22 | | X | X | | X
23 | X | X | X | | X
24 | | | | X | X
25 | X | | | X | X
26 | | X | | X | X
27 | X | X | | X | X
28 | | X | X | X | X
29 | X | X | X | X | X
30 | | X | X | X | X
31 | X | X | X | X | X
-L SIZE
Limit the size of the output file to SIZE bytes. An incomplete
DUMPFILE or LOGFILE is written if the size would otherwise
exceed SIZE.
-E Create DUMPFILE in the ELF format.
This option cannot be specified with the -c, -l or -p options,
because the ELF format does not support compressed data.
Example:
# makedumpfile -E -d 31 -x vmlinux /proc/vmcore dumpfile
-f Force existing DUMPFILE to be overwritten and mem-usage to work
with older kernel as well.
Example:
# makedumpfile -f -d 31 -x vmlinux /proc/vmcore dumpfile
This command overwrites DUMPFILE even if it already exists.
# makedumpfile -f --mem-usage /proc/kcore
Kernel version lesser than v4.11 will not work with --mem-usage
functionality until it has been patched with upstream commit
464920104bf7. Therefore if you have patched your older kernel
then use -f.
-x VMLINUX
Specify the first kernel's VMLINUX with debug information to
analyze the first kernel's memory usage.
This option is necessary if VMCORE does not contain VMCOREINFO,
[-i VMCOREINFO] is not specified, and dump_level is 2 or more.
The page size of the first kernel and the second kernel should
match.
Example:
# makedumpfile -d 31 -x vmlinux /proc/vmcore dumpfile
-i VMCOREINFO
Specify VMCOREINFO instead of VMLINUX for analyzing the first
kernel's memory usage.
VMCOREINFO should be made beforehand by makedumpfile with -g
option, and it contains the first kernel's information.
This option is necessary if VMCORE does not contain VMCOREINFO,
[-x VMLINUX] is not specified, and dump_level is 2 or more.
Example:
# makedumpfile -d 31 -i vmcoreinfo /proc/vmcore dumpfile
-g VMCOREINFO
Generate VMCOREINFO from the first kernel's VMLINUX with debug
information.
VMCOREINFO must be generated on the system that is running the
first kernel. With -i option, a user can specify VMCOREINFO gen-
erated on the other system that is running the same first ker-
nel. [-x VMLINUX] must be specified.
Example:
# makedumpfile -g vmcoreinfo -x vmlinux
--config FILTERCONFIGFILE
Used in conjunction with -x VMLINUX option, to specify the fil-
ter config file FILTERCONFIGFILE that contains erase commands to
filter out desired kernel data from vmcore while creating DUMP-
FILE. For filter command syntax please refer to makedump-
file.conf(5).
--eppic EPPICMACRO
Used in conjunction with -x VMLINUX option, to specify the eppic
macro file that contains filter rules or directory that contains
eppic macro files to filter out desired kernel data from vmcore
while creating DUMPFILE. When directory is specified, all the
eppic macros in the directory are processed.
-F Output the dump data in the flattened format to the standard
output for transporting the dump data by SSH.
Analysis tools (crash utility before version 5.1.2 or GDB) can-
not read the flattened format directly. For analysis, the dump
data in the flattened format should be rearranged to a normal
DUMPFILE (readable with analysis tools) by -R option. By which
option is specified with -F option, the format of the rearranged
DUMPFILE is fixed. In other words, it is impossible to specify
the DUMPFILE format when the dump data is rearranged with -R
option. If specifying -E option with -F option, the format of
the rearranged DUMPFILE is the ELF format. Otherwise, it is the
kdump-compressed format. All the messages are output to standard
error output by -F option because standard output is used for
the dump data.
Example:
# makedumpfile -F -c -d 31 -x vmlinux /proc/vmcore \
| ssh user@host "cat > dumpfile.tmp"
# makedumpfile -F -c -d 31 -x vmlinux /proc/vmcore \
| ssh user@host "makedumpfile -R dumpfile"
# makedumpfile -F -E -d 31 -i vmcoreinfo /proc/vmcore \
| ssh user@host "makedumpfile -R dumpfile"
# makedumpfile -F -E --xen-vmcoreinfo VMCOREINFO /proc/vmcore \
| ssh user@host "makedumpfile -R dumpfile"
-R Rearrange the dump data in the flattened format from the stan-
dard input to a normal DUMPFILE (readable with analysis tools).
Example:
# makedumpfile -R dumpfile < dumpfile.tmp
# makedumpfile -F -d 31 -x vmlinux /proc/vmcore \
| ssh user@host "makedumpfile -R dumpfile"
Instead of using -R option, a perl script "makedumpfile-R.pl"
rearranges the dump data in the flattened format to a normal
DUMPFILE, too. The perl script does not depend on architecture,
and most systems have perl command. Even if a remote host does
not have makedumpfile, it is possible to rearrange the dump data
in the flattened format to a readable DUMPFILE on a remote host
by running this script.
Example:
# makedumpfile -F -d 31 -x vmlinux /proc/vmcore \
| ssh user@host "makedumpfile-R.pl dumpfile"
--split
Split the dump data to multiple DUMPFILEs in parallel. If speci-
fying DUMPFILEs on different storage devices, a device can share
I/O load with other devices and it reduces time for saving the
dump data. The file size of each DUMPFILE is smaller than the
system memory size which is divided by the number of DUMPFILEs.
This feature supports only the kdump-compressed format.
Example:
# makedumpfile --split -d 31 -x vmlinux /proc/vmcore dumpfile1
dumpfile2
--num-threads THREADNUM
Using multiple threads to read and compress data of each page in
parallel. And it will reduces time for saving DUMPFILE. Note
that if the usable cpu number is less than the thread number, it
may lead to great performance degradation. This feature only
supports creating DUMPFILE in kdump-comressed format from VMCORE
in kdump-compressed format or elf format.
Example:
# makedumpfile -d 31 --num-threads 4 /proc/vmcore dumpfile
--reassemble
Reassemble multiple DUMPFILEs, which are created by --split
option, into one DUMPFILE. dumpfile1 and dumpfile2 are reassem-
bled into dumpfile on the following example.
Example:
# makedumpfile --reassemble dumpfile1 dumpfile2 dumpfile
-b <order>
Cache 2^order pages in ram when generating DUMPFILE before writ-
ing to output. The default value is 4.
--cyclic-buffer buffer_size
Specify the buffer size in kilo bytes for bitmap data. Filter-
ing processing will be divided into multi cycles to fix the mem-
ory consumption, the number of cycles is represented as:
num_of_cycles = system_memory / (buffer_size * 1024 *
bit_per_bytes * page_size )
The lesser number of cycles, the faster working speed is
expected. By default, buffer_size will be calculated automati-
cally depending on system memory size, so ordinary users don't
need to specify this option.
Example:
# makedumpfile --cyclic-buffer 1024 -d 31 -x vmlinux
/proc/vmcore dumpfile
--splitblock-size splitblock_size
Specify the splitblock size in kilo bytes for analysis with
--split. If --splitblock N is specified, difference of each
splitted dumpfile size is at most N kilo bytes.
Example:
# makedumpfile --splitblock-size 1024 -d 31 -x vmlinux --split
/proc/vmcore dumpfile1 dumpfile2
--work-dir
Specify the working directory for the temporary bitmap file. If
this option isn't specified, the bitmap will be saved on memory.
Filtering processing has to do 2 pass scanning to fix the memory
consumption, but it can be avoided by using working directory on
file system. So if you specify this option, the filtering speed
may be bit faster.
Example:
# makedumpfile --work-dir /tmp -d 31 -x vmlinux /proc/vmcore
dumpfile
--non-mmap
Never use mmap(2) to read VMCORE even if it supports mmap(2).
Generally, reading VMCORE with mmap(2) is faster than without
it, so ordinary users don't need to specify this option. This
option is mainly for debugging.
Example:
# makedumpfile --non-mmap -d 31 -x vmlinux /proc/vmcore dumpfile
--xen-syms XEN-SYMS
Specify the XEN-SYMS with debug information to analyze the xen's
memory usage. This option extracts the part of xen and
domain-0.
Example:
# makedumpfile -E --xen-syms xen-syms /proc/vmcore dumpfile
--xen-vmcoreinfo VMCOREINFO
Specify VMCOREINFO instead of XEN-SYMS for analyzing the xen's
memory usage.
VMCOREINFO should be made beforehand by makedumpfile with -g
option, and it contains the xen's information.
Example:
# makedumpfile -E --xen-vmcoreinfo VMCOREINFO /proc/vmcore dump-
file
-X Exclude all the user domain pages from Xen kdump's VMCORE, and
extracts the part of xen and domain-0. If VMCORE contains VMCOR-
EINFO for Xen, it is not necessary to specify --xen-syms and
--xen-vmcoreinfo.
Example:
# makedumpfile -E -X /proc/vmcore dumpfile
--xen_phys_start xen_phys_start_address
This option is only for x86_64. Specify the
xen_phys_start_address, if the xen code/data is relocatable and
VMCORE does not contain xen_phys_start_address in the CRASHINFO.
xen_phys_start_address can be taken from the line of "Hypervisor
code and data" in /proc/iomem. For example, specify 0xcee00000
as xen_phys_start_address if /proc/iomem is the following:
-------------------------------------------------------
# cat /proc/iomem
...
cee00000-cfd99999 : Hypervisor code and data
...
-------------------------------------------------------
Example:
# makedumpfile -E -X --xen_phys_start 0xcee00000 /proc/vmcore
dumpfile
--message-level message_level
Specify the message types.
Users can restrict outputs printed by specifying message_level
with this option. The message type marked with an X in the fol-
lowing table is printed. For example, according to the table,
specifying 7 as message_level means progress indicator, common
message, and error message are printed, and this is a default
value. Note that the maximum value of message_level is 31.
message | progress | common | error | debug | report
level | indicator| message | message | message | message
---------+----------+---------+---------+---------+---------
0 | | | | |
1 | X | | | |
2 | | X | | |
3 | X | X | | |
4 | | | X | |
5 | X | | X | |
6 | | X | X | |
* 7 | X | X | X | |
8 | | | | X |
9 | X | | | X |
10 | | X | | X |
11 | X | X | | X |
12 | | | X | X |
13 | X | | X | X |
14 | | X | X | X |
15 | X | X | X | X |
16 | | | | | X
17 | X | | | | X
18 | | X | | | X
19 | X | X | | | X
20 | | | X | | X
21 | X | | X | | X
22 | | X | X | | X
23 | X | X | X | | X
24 | | | | X | X
25 | X | | | X | X
26 | | X | | X | X
27 | X | X | | X | X
28 | | | X | X | X
29 | X | | X | X | X
30 | | X | X | X | X
31 | X | X | X | X | X
--vtop virtual_address
This option is useful, when user debugs the translation problem
of virtual address. If specifing virtual_address, its physical
address is printed. It makes debugging easy by comparing the
output of this option with the one of "vtop" subcommand of the
crash utility. "--vtop" option only prints the translation out-
put, and it does not affect the dumpfile creation.
--dump-dmesg
This option overrides the normal behavior of makedumpfile.
Instead of compressing and filtering a VMCORE to make it
smaller, it simply extracts the dmesg log from a VMCORE and
writes it to the specified LOGFILE. If a VMCORE does not contain
VMCOREINFO for dmesg, it is necessary to specfiy [-x VMLINUX] or
[-i VMCOREINFO].
Example:
# makedumpfile --dump-dmesg /proc/vmcore dmesgfile
# makedumpfile --dump-dmesg -x vmlinux /proc/vmcore dmesgfile
--partial-dmesg
This option will make --dump-dmesg extract only dmesg logs since
that buffer was last cleared on the crashed kernel, through
"dmesg --clear" for example.
--mem-usage
This option is currently supported on x86_64, arm64, ppc64 and
s390x. This option is used to show the page numbers of current
system in different use. It should be executed in 1st kernel. By
the help of this, user can know how many pages is dumpable when
different dump_level is specified. It analyzes the 'System Ram'
and 'kernel text' program segment of /proc/kcore excluding the
crashkernel range, then calculates the page number of different
kind per vmcoreinfo. So currently /proc/kcore need be specified
explicitly.
Example:
# makedumpfile --mem-usage /proc/kcore
--diskset=VMCORE
Specify multiple VMCOREs created on sadump diskset configuration
the same number of times as the number of VMCOREs in increasing
order from left to right. VMCOREs are assembled into a single
DUMPFILE.
Example:
# makedumpfile -x vmlinux --diskset=vmcore1 --diskset=vmcore2
dumpfile
-D Print debugging message.
-h (--help)
Show help message and LZO/snappy support status (enabled/dis-
abled).
-v Show the version of makedumpfile.
--check-params
Only check whether the command-line parameters are valid or not,
and exit. Preferable to be given as the first parameter.
--dry-run
Do not write the output dump file while still performing opera-
tions specified by other options. This option cannot be used
with the --dump-dmesg, --reassemble and -g options.
--show-stats
Display report messages. This is an alternative to enabling bit
4 in the level provided to --message-level.
ENVIRONMENT VARIABLES
TMPDIR This environment variable is used in 1st kernel environment for
a temporary memory bitmap file. If your machine has a lots of
memory and you use small tmpfs on /tmp, makedumpfile can fail
for a little memory because makedumpfile makes a very large
temporary memory bitmap file in this case. To avoid this fail-
ure, you should specify --work-dir option to use file system on
storage for the bitmap file.
DIAGNOSTICS
makedumpfile exits with the following value.
0 : makedumpfile succeeded.
1 : makedumpfile failed without the following reasons.
2 : makedumpfile failed due to the different version between VMLINUX
and VMCORE.
AUTHORS
Written by Masaki Tachibana, and Ken'ichi Ohmichi.
SEE ALSO
crash(8), gdb(1), kexec(8), makedumpfile.conf(5)
makedumpfile v1.7.2 20 Oct 2022 MAKEDUMPFILE(8)
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