kdump(1)

NAME

kdump - display kernel trace data

SYNOPSIS

kdump [-dEnlHRsT] [-f trfile]  [-m  maxdata]  [-p  pid]  [-t
[cnisuw]]

DESCRIPTION

The kdump command displays the kernel trace files produced

with ktrace(1)
in human readable format. By default, the file ktrace.out

in the current
directory is displayed.

The options are as follows:

-d Display all numbers in decimal.

-E Display elapsed timestamps (time since beginning

of trace).

-f trfile Display the specified file instead of

ktrace.out.

-H List the thread ID (tid) of the thread with each

trace

record, if available. If no thread ID is avail

able, 0 will
be printed.

-l Loop reading the trace file, once the end-of

file is reached,

waiting for more data.

-m maxdata Display at most maxdata bytes when decoding I/O.

-n Suppress ad hoc translations. Normally kdump

tries to decode

many system calls into a more human readable

format. For
example, ioctl(2) values are replaced with the

macro name and
errno values are replaced with the strerror(3)

string. Suppressing this feature yields a more consistent

output format
and is easily amenable to further processing.

-p pid Display only trace events that correspond to the

process pid.

This may be useful when there are multiple pro

cesses recorded
in the same trace file.

-R Display relative timestamps (time since previous

entry).

-s Suppress display of I/O data.

-T Display absolute timestamps for each entry (sec

onds since

epoch).

-t cnisuw See the -t option of ktrace(1).

The output format of kdump is line oriented with several

fields. The
example below shows a section of a kdump generated by the

following commands:

?> ktrace echo "ktrace"

?> kdump

85045 echo CALL writev(0x1,0x804b030,0x2)
85045 echo GIO fd 1 wrote 7 bytes

"ktrace
"

85045 echo RET writev 7

The first field is the PID of the process being traced. The

second field
is the name of the program being traced. The third field is

the operation that the kernel performed on behalf of the process. If

thread IDs
are being printed, then an additional thread ID column will

be added to
the output between the PId field and program name field.

In the first line above, the kernel executes the writev(2)

system call on
behalf of the process so this is a CALL operation. The

fourth field
shows the system call that was executed, including its argu

ments. The
writev(2) system call takes a file descriptor, in this case

1, or standard output, then a pointer to the iovector to write, and

the number of
iovectors that are to be written. In the second line we see

the operation was GIO, for general I/O, and that file descriptor 1

had seven bytes
written to it. This is followed by the seven bytes that

were written,
the string "ktrace" with a carriage return and line feed.

The last line
is the RET operation, showing a return from the kernel, what

system call
we are returning from, and the return value that the process

received.
Seven bytes were written by the writev(2) system call, so 7

is the return
value.

The possible operations are:

Name Operation Fourth

field
CALL enter syscall syscall

name and

arguments

RET return from syscall syscall

name and return

value

NAMI file name lookup path to

file
GENIO general I/O fd,

read/write, number

of bytes

SIG signal signal

name, handler,

mask, code

CSW context switch stop/resume

user/kernel
USER data from user process the data

SEE ALSO

ktrace(1)

HISTORY

The kdump command appeared in 4.4BSD.

BSD February 14, 2006

BSD