makedumpfile - make a small dumpfile of kdump
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 DUMPFILE1 DUMPFILE2
[
DUMPFILE3 ..]
makedumpfile [
OPTION] [-x
VMLINUX|-i
VMCOREINFO]
--num-threads
THREADNUM VMCORE DUMPFILE
makedumpfile --reassemble
DUMPFILE1 DUMPFILE2
[
DUMPFILE3 ..]
DUMPFILE
makedumpfile -g
VMCOREINFO -x
VMLINUX
makedumpfile [
OPTION] [--xen-syms
XEN-SYMS|--xen-vmcoreinfo
VMCOREINFO]
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
With kdump, the memory image of the first kernel (called "panicked
kernel") can be taken as /proc/vmcore while the second kernel (called
"kdump kernel" or "capture kernel") is running. This
document represents /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, makedumpfile
allows user to filter out targeted kernel data. The filter config file can be
used to specify kernel/module symbols and its members 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 character '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 operators, functions,
nested loops to traverse and erase kernel data. --eppic requires
eppic_makedumpfile.so and eppic library.
eppic_makedumpfile.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
DUMPFILE 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: single
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.
- -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 specify 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 ',', makedumpfile
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 generated on
the other system that is running the same first kernel. [-x
VMLINUX] must be specified.
Example:
# makedumpfile -g vmcoreinfo -x vmlinux
-
--config FILTERCONFIGFILE
- Used in conjunction with -x VMLINUX option, to
specify the filter config file FILTERCONFIGFILE that contains erase
commands to filter out desired kernel data from vmcore while creating
DUMPFILE. For filter command syntax please refer to
makedumpfile.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) cannot 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
standard 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 specifying 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
reassembled into dumpfile on the following example.
Example:
# makedumpfile --reassemble dumpfile1 dumpfile2 dumpfile
-
-b <order>
- Cache 2^order pages in ram when generating DUMPFILE
before writing to output. The default value is 4.
-
--cyclic-buffer buffer_size
- Specify the buffer size in kilo bytes for bitmap data.
Filtering processing will be divided into multi cycles to fix the memory
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 automatically 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 dumpfile
- -X
- Exclude all the user domain pages from Xen kdump's
VMCORE, and extracts the part of xen and domain-0. If VMCORE
contains VMCOREINFO 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 following 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
output, 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/disabled).
- -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
operations 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.
- 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 failure, you should specify --work-dir option to
use file system on storage for the bitmap file.
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.
-
Written by Masaki Tachibana, and Ken'ichi Ohmichi.
crash(8),
gdb(1),
kexec(8),
makedumpfile.conf(5)