xref: /freebsd/usr.bin/ktrace/ktrace.1 (revision 8d20be1e22095c27faf8fe8b2f0d089739cc742e)
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28.\"	@(#)ktrace.1	8.1 (Berkeley) 6/6/93
29.\" $FreeBSD$
30.\"
31.Dd May 31, 2012
32.Dt KTRACE 1
33.Os
34.Sh NAME
35.Nm ktrace
36.Nd enable kernel process tracing
37.Sh SYNOPSIS
38.Nm
39.Op Fl aCcdi
40.Op Fl f Ar trfile
41.Op Fl g Ar pgrp | Fl p Ar pid
42.Op Fl t Ar trstr
43.Nm
44.Op Fl adi
45.Op Fl f Ar trfile
46.Op Fl t Ar trstr
47.Ar command
48.Sh DESCRIPTION
49The
50.Nm
51utility enables kernel trace logging for the specified processes.
52Kernel trace data is logged to the file
53.Pa ktrace.out .
54The kernel operations that are traced include system calls, namei
55translations, signal processing, and
56.Tn I/O .
57.Pp
58Once tracing is enabled on a process, trace data will be logged until
59either the process exits or the trace point is cleared.
60A traced process can generate enormous amounts of log data quickly;
61It is strongly suggested that users memorize how to disable tracing before
62attempting to trace a process.
63The following command is sufficient to disable tracing on all user-owned
64processes, and, if executed by root, all processes:
65.Pp
66.Dl \&$ ktrace -C
67.Pp
68The trace file is not human readable; use
69.Xr kdump 1
70to decode it.
71.Pp
72The utility may be used only with a kernel that has been built with the
73.Dq KTRACE
74option in the kernel configuration file.
75.Pp
76The options are:
77.Bl -tag -width indent
78.It Fl a
79Append to the trace file instead of recreating it.
80.It Fl C
81Disable tracing on all user-owned processes, and, if executed by root, all
82processes in the system.
83.It Fl c
84Clear the trace points associated with the specified file or processes.
85.It Fl d
86Descendants; perform the operation for all current children of the
87designated processes.
88.It Fl f Ar trfile
89Log trace records to
90.Ar trfile
91instead of
92.Pa ktrace.out .
93.It Fl g Ar pgid
94Enable (disable) tracing on all processes in the process group (only one
95.Fl g
96flag is permitted).
97.It Fl i
98Inherit; pass the trace flags to all future children of the designated
99processes.
100.It Fl p Ar pid
101Enable (disable) tracing on the indicated process id (only one
102.Fl p
103flag is permitted).
104.It Fl t Ar trstr
105The string argument represents the kernel trace points, one per letter.
106The following table equates the letters with the tracepoints:
107.Pp
108.Bl -tag -width flag -compact
109.It Cm c
110trace system calls
111.It Cm f
112trace page faults
113.It Cm i
114trace
115.Tn I/O
116.It Cm n
117trace namei translations
118.It Cm p
119trace capability check failures
120.It Cm s
121trace signal processing
122.It Cm t
123trace various structures
124.It Cm u
125userland traces
126.It Cm w
127context switches
128.It Cm y
129trace
130.Xr sysctl 3
131requests
132.It Cm +
133trace the default set of trace points -
134.Cm c , i , n , p , s , t , u , y
135.El
136.It Ar command
137Execute
138.Ar command
139with the specified trace flags.
140.El
141.Pp
142The
143.Fl p ,
144.Fl g ,
145and
146.Ar command
147options are mutually exclusive.
148.Sh EXAMPLES
149# trace all kernel operations of process id 34
150.Dl $ ktrace -p 34
151.Pp
152# trace all kernel operations of processes in process group 15 and
153# pass the trace flags to all current and future children
154.Dl $ ktrace -idg 15
155.Pp
156# disable all tracing of process 65
157.Dl $ ktrace -cp 65
158.Pp
159# disable tracing signals on process 70 and all current children
160.Dl $ ktrace -t s -cdp 70
161.Pp
162# enable tracing of
163.Tn I/O
164on process 67
165.Dl $ ktrace -ti -p 67
166.Pp
167# run the command "w", tracing only system calls
168.Dl $ ktrace -tc w
169.Pp
170# disable all tracing to the file "tracedata"
171.Dl $ ktrace -c -f tracedata
172.Pp
173# disable tracing of all user-owned processes
174.Dl $ ktrace -C
175.Sh SEE ALSO
176.Xr kdump 1
177.Sh HISTORY
178The
179.Nm
180command appeared in
181.Bx 4.4 .
182.Sh BUGS
183Only works if
184.Ar trfile
185is a regular file.
186