paxmirabilis/src/cpio.1

.\"     $MirOS: src/bin/pax/cpio.1,v 1.15 2006/07/21 17:34:59 tg Exp $
.\"     $OpenBSD: cpio.1,v 1.23 2006/01/03 17:22:47 jmc Exp $
.\"
.\" Copyright (c) 2005 Thorsten Glaser <tg@66h.42h.de>
.\" Copyright (c) 1997 SigmaSoft, Th. Lockert
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd July 21, 2006
.Dt CPIO 1
.Os MirBSD
.\" for portability
.de Mx
.nr cF \\n(.f
.nr cZ \\n(.s
.ds aa \&\f\\n(cF\s\\n(cZ
.if \\n(aC==0 \{\
.       ie \\n(.$==0 \&MirOS\\*(aa
.       el .aV \\$1 \\$2 \\$3 \\$4 \\$5 \\$6 \\$7 \\$8 \\$9
.\}
.if \\n(aC>\\n(aP \{\
.       nr aP \\n(aP+1
.       ie \\n(C\\n(aP==2 \{\
.               as b1 \&MirOS\ #\&\\*(A\\n(aP\\*(aa
.               ie \\n(aC>\\n(aP \{\
.                       nr aP \\n(aP+1
.                       nR
.               \}
.               el .aZ
.       \}
.       el \{\
.               as b1 \&MirOS\\*(aa
.               nR
.       \}
.\}
..
.Sh NAME
.Nm cpio
.Nd copy file archives in and out
.Sh SYNOPSIS
.Nm cpio
.Fl o
.Op Fl aABcLvzZ
.Op Fl C Ar bytes
.Op Fl F Ar archive
.Op Fl H Ar format
.Op Fl M Ar flag
.Op Fl O Ar archive
.Ar "< name-list"
.Op Ar "> archive"
.Nm cpio
.Fl i
.Op Fl bBcdfmrsStuvzZ6
.Op Fl C Ar bytes
.Op Fl E Ar file
.Op Fl F Ar archive
.Op Fl H Ar format
.Op Fl I Ar archive
.Op Ar "pattern ..."
.Op Ar "< archive"
.Nm cpio
.Fl p
.Op Fl adlLmuv
.Ar destination-directory
.Ar "< name-list"
.Sh DESCRIPTION
The
.Nm
command copies files to and from a
.Nm
archive.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl o
Create an archive.
Reads the list of files to store in the
archive from standard input, and writes the archive on standard
output.
.Bl -tag -width Ds
.It Fl a
Reset the access times on files that have been copied to the
archive.
.It Fl A
Append to the specified archive.
.It Fl B
Set block size of output to 5120 bytes.
.It Fl c
Use ASCII format for
.Nm
header for portability.
.It Fl C Ar bytes
Set the block size of output to
.Ar bytes .
.It Fl F Ar archive
.It Fl O Ar archive
Use the specified file name as the archive to write to.
.It Fl H Ar format
Write the archive in the specified format.
Recognised formats are:
.Pp
.Bl -tag -width sv4cpio -compact
.It Ar bcpio
Old binary
.Nm
format.
Selected by
.Fl 6 .
.It Ar cpio
Old octal character
.Nm
format.
Selected by
.Fl c .
.It Ar sv4cpio
SVR4 hex
.Nm
format.
.It Ar sv4crc
SVR4 hex
.Nm
format with checksums.
This is the default format for creating new archives.
.It Ar tar
Old tar format.
.It Ar ustar
POSIX ustar format.
.It "\ "
.It Ar bin
These
.It Ar crc
four
.It Ar newc
formats
.It Ar odc
are supported for backwards compatibility only.
.El
.It Fl L
Follow symbolic links.
.It Fl M Ar flag
Configure the archive normaliser.
.Ar flag
is either a numeric value compatible to
.Xr strtonum 3
which is directly stored in the flags word, or
one of the following values, prefixed with
.Dq no-
to turn them off, or not, to turn them on:
.Pp
.Bl -tag -width xxxxxx -compact
.It Ar inodes
0x0001: Serialise inodes, zero device info.
.It Ar links
0x0002: Store content of hard links only once.
.It Ar mtime
0x0004: Zero out the file modification time.
.It Ar uidgid
0x0008: Set owner to 0:0 (root:wheel).
.It Ar dist
0x000B: Clean everything except mtime.
.It Ar set
0x0003: Keep ownership and mtime intact.
.It Ar norm
0x000F: Clean everything.
.It Ar root
0x0009: Clean owner and device information.
.It Ar verb
0x0010: Debug this option.
.It Ar debug
0x0020: Debug file header storage.
.El
.Pp
This option is only implemented for the cpio, sv4cpio,
sv4crc, and ustar file format writing routines.
For the ustar format, the
.Ar inodes
and
.Ar links
specifiers are ignored.
.It Fl v
Be verbose about operations.
List filenames as they are written to the archive.
.It Fl z
Compress archive using
.Xr gzip 1
format.
.It Fl Z
Compress archive using
.Xr compress 1
format.
.El
.It Fl i
Restore files from an archive.
Reads the archive file from
standard input and extracts files matching the
.Ar patterns
that were specified on the command line.
.Bl -tag -width Ds
.It Fl b
Do byte and word swapping after reading in data from the
archive, for restoring archives created on systems with
a different byte order.
.It Fl B
Set the block size of the archive being read to 5120 bytes.
.It Fl c
Expect the archive headers to be in ASCII format.
.It Fl C Ar bytes
Read archive written with a block size of
.Ar bytes .
.It Fl d
Create any intermediate directories as needed during
restore.
.It Fl E Ar file
Read list of file name patterns to extract or list from
.Ar file .
.It Fl f
Restore all files except those matching the
.Ar patterns
given on the command line.
.It Fl F Ar archive
.It Fl I Ar archive
Use the specified file as the input for the archive.
.It Fl H Ar format
Read an archive of the specified format.
Recognised formats are:
.Pp
.Bl -tag -width sv4cpio -compact
.It Ar bcpio
Old binary
.Nm
format.
.It Ar cpio
Old octal character
.Nm
format.
.It Ar sv4cpio
SVR4 hex
.Nm
format.
.It Ar sv4crc
SVR4 hex
.Nm
format with checksums.
.It Ar tar
Old tar format.
.It Ar ustar
POSIX ustar format.
.It "\ "
.It Ar bin
These
.It Ar crc
four
.It Ar newc
formats
.It Ar odc
are supported for backwards compatibility only.
.El
.It Fl m
Restore modification times on files.
.It Fl r
Rename restored files interactively.
.It Fl s
Swap bytes after reading data from the archive.
.It Fl S
Swap words after reading data from the archive.
.It Fl t
Only list the contents of the archive, no files or
directories will be created.
.It Fl u
Overwrite files even when the file in the archive is
older than the one that will be overwritten.
.It Fl v
Be verbose about operations.
List filenames as they are copied in from the archive.
.It Fl z
Uncompress archive using
.Xr gzip 1
format.
.It Fl Z
Uncompress archive using
.Xr compress 1
format.
.It Fl 6
Process old-style
.Nm
format archives.
.El
.It Fl p
Copy files from one location to another in a single pass.
The list of files to copy are read from standard input and
written out to a directory relative to the specified
.Ar directory
argument.
.Bl -tag -width Ds
.It Fl a
Reset the access times on files that have been copied.
.It Fl d
Create any intermediate directories as needed to write
the files at the new location.
.It Fl l
When possible, link files rather than creating an
extra copy.
.It Fl L
Follow symbolic links.
.It Fl m
Restore modification times on files.
.It Fl u
Overwrite files even when the original file being copied is
older than the one that will be overwritten.
.It Fl v
Be verbose about operations.
List filenames as they are copied.
.El
.El
.Sh ENVIRONMENT
.Bl -tag -width Fl
.It Ev TMPDIR
Path in which to store temporary files.
.El
.Sh ERRORS
.Nm
will exit with one of the following values:
.Bl -tag -width 2n
.It 0
All files were processed successfully.
.It 1
An error occurred.
.El
.Pp
Whenever
.Nm
cannot create a file or a link when extracting an archive or cannot
find a file while writing an archive, or cannot preserve the user
ID, group ID, file mode, or access and modification times when the
.Fl p
option is specified, a diagnostic message is written to standard
error and a non-zero exit value will be returned, but processing
will continue.
In the case where
.Nm
cannot create a link to a file,
.Nm
will not create a second copy of the file.
.Pp
If the extraction of a file from an archive is prematurely terminated
by a signal or error,
.Nm
may have only partially extracted the file the user wanted.
Additionally, the file modes of extracted files and directories may
have incorrect file bits, and the modification and access times may
be wrong.
.Pp
If the creation of an archive is prematurely terminated by a signal
or error,
.Nm
may have only partially created the archive, which may violate the
specific archive format specification.
.Sh SEE ALSO
.Xr pax 1 ,
.Xr tar 1
.Sh AUTHORS
Keith Muller at the University of California, San Diego.
.Sh CAVEATS
Different file formats have different maximum file sizes.
It is recommended that a format such as cpio or ustar
be used for larger files.
.Pp
.Bl -column "File format" "Maximum file size" -offset indent -compact
.It Sy "File format" Ta Sy "Maximum file size"
.It bcpio Ta 4 Gibibytes
.It sv4cpio Ta 4 Gibibytes
.It cpio Ta 8 Gibibytes
.It tar Ta 8 Gibibytes
.It ustar Ta 8 Gibibytes
.El
.Sh BUGS
The
.Fl s
and
.Fl S
options are currently not implemented.
.Sh CAVEATS
The backwards-compatible format options are not available in the
.Xr pax 1
front-end.
.Pp
The
.Fl M
option is a MirBSD extensions, available starting with
.Mx 8 .
Archives written using these options are, however, compatible to
the standard and should be readable on any other system.
The only option whose behaviour is not explicitly allowed by the
standard is hard link unification (write file contens only once)
selected by
.Fl M Ar 0x0002 .
// Log In
// CVSweb
Project: FreeWRT
// Summary // Activity // Search // Tracker // Lists // News // SCM // Wiki
1	.\" $MirOS: src/bin/pax/cpio.1,v 1.15 2006/07/21 17:34:59 tg Exp $
2	.\" $OpenBSD: cpio.1,v 1.23 2006/01/03 17:22:47 jmc Exp $
3	.\"
4	.\" Copyright (c) 2005 Thorsten Glaser <tg@66h.42h.de>
5	.\" Copyright (c) 1997 SigmaSoft, Th. Lockert
6	.\" All rights reserved.
7	.\"
8	.\" Redistribution and use in source and binary forms, with or without
9	.\" modification, are permitted provided that the following conditions
10	.\" are met:
11	.\" 1. Redistributions of source code must retain the above copyright
12	.\" notice, this list of conditions and the following disclaimer.
13	.\" 2. Redistributions in binary form must reproduce the above copyright
14	.\" notice, this list of conditions and the following disclaimer in the
15	.\" documentation and/or other materials provided with the distribution.
16	.\"
17	.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18	.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19	.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20	.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21	.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22	.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23	.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24	.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25	.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26	.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27	.\"
28	.Dd July 21, 2006
29	.Dt CPIO 1
30	.Os MirBSD
31	.\" for portability
32	.de Mx
33	.nr cF \\n(.f
34	.nr cZ \\n(.s
35	.ds aa \&\f\\n(cF\s\\n(cZ
36	.if \\n(aC==0 \{\
37	. ie \\n(.$==0 \&MirOS\\*(aa
38	. el .aV \\$1 \\$2 \\$3 \\$4 \\$5 \\$6 \\$7 \\$8 \\$9
39	.\}
40	.if \\n(aC>\\n(aP \{\
41	. nr aP \\n(aP+1
42	. ie \\n(C\\n(aP==2 \{\
43	. as b1 \&MirOS\ #\&\\(A\\n(aP\\(aa
44	. ie \\n(aC>\\n(aP \{\
45	. nr aP \\n(aP+1
46	. nR
47	. \}
48	. el .aZ
49	. \}
50	. el \{\
51	. as b1 \&MirOS\\*(aa
52	. nR
53	. \}
54	.\}
55	..
56	.Sh NAME
57	.Nm cpio
58	.Nd copy file archives in and out
59	.Sh SYNOPSIS
60	.Nm cpio
61	.Fl o
62	.Op Fl aABcLvzZ
63	.Op Fl C Ar bytes
64	.Op Fl F Ar archive
65	.Op Fl H Ar format
66	.Op Fl M Ar flag
67	.Op Fl O Ar archive
68	.Ar "< name-list"
69	.Op Ar "> archive"
70	.Nm cpio
71	.Fl i
72	.Op Fl bBcdfmrsStuvzZ6
73	.Op Fl C Ar bytes
74	.Op Fl E Ar file
75	.Op Fl F Ar archive
76	.Op Fl H Ar format
77	.Op Fl I Ar archive
78	.Op Ar "pattern ..."
79	.Op Ar "< archive"
80	.Nm cpio
81	.Fl p
82	.Op Fl adlLmuv
83	.Ar destination-directory
84	.Ar "< name-list"
85	.Sh DESCRIPTION
86	The
87	.Nm
88	command copies files to and from a
89	.Nm
90	archive.
91	.Pp
92	The options are as follows:
93	.Bl -tag -width Ds
94	.It Fl o
95	Create an archive.
96	Reads the list of files to store in the
97	archive from standard input, and writes the archive on standard
98	output.
99	.Bl -tag -width Ds
100	.It Fl a
101	Reset the access times on files that have been copied to the
102	archive.
103	.It Fl A
104	Append to the specified archive.
105	.It Fl B
106	Set block size of output to 5120 bytes.
107	.It Fl c
108	Use ASCII format for
109	.Nm
110	header for portability.
111	.It Fl C Ar bytes
112	Set the block size of output to
113	.Ar bytes .
114	.It Fl F Ar archive
115	.It Fl O Ar archive
116	Use the specified file name as the archive to write to.
117	.It Fl H Ar format
118	Write the archive in the specified format.
119	Recognised formats are:
120	.Pp
121	.Bl -tag -width sv4cpio -compact
122	.It Ar bcpio
123	Old binary
124	.Nm
125	format.
126	Selected by
127	.Fl 6 .
128	.It Ar cpio
129	Old octal character
130	.Nm
131	format.
132	Selected by
133	.Fl c .
134	.It Ar sv4cpio
135	SVR4 hex
136	.Nm
137	format.
138	.It Ar sv4crc
139	SVR4 hex
140	.Nm
141	format with checksums.
142	This is the default format for creating new archives.
143	.It Ar tar
144	Old tar format.
145	.It Ar ustar
146	POSIX ustar format.
147	.It "\ "
148	.It Ar bin
149	These
150	.It Ar crc
151	four
152	.It Ar newc
153	formats
154	.It Ar odc
155	are supported for backwards compatibility only.
156	.El
157	.It Fl L
158	Follow symbolic links.
159	.It Fl M Ar flag
160	Configure the archive normaliser.
161	.Ar flag
162	is either a numeric value compatible to
163	.Xr strtonum 3
164	which is directly stored in the flags word, or
165	one of the following values, prefixed with
166	.Dq no-
167	to turn them off, or not, to turn them on:
168	.Pp
169	.Bl -tag -width xxxxxx -compact
170	.It Ar inodes
171	0x0001: Serialise inodes, zero device info.
172	.It Ar links
173	0x0002: Store content of hard links only once.
174	.It Ar mtime
175	0x0004: Zero out the file modification time.
176	.It Ar uidgid
177	0x0008: Set owner to 0:0 (root:wheel).
178	.It Ar dist
179	0x000B: Clean everything except mtime.
180	.It Ar set
181	0x0003: Keep ownership and mtime intact.
182	.It Ar norm
183	0x000F: Clean everything.
184	.It Ar root
185	0x0009: Clean owner and device information.
186	.It Ar verb
187	0x0010: Debug this option.
188	.It Ar debug
189	0x0020: Debug file header storage.
190	.El
191	.Pp
192	This option is only implemented for the cpio, sv4cpio,
193	sv4crc, and ustar file format writing routines.
194	For the ustar format, the
195	.Ar inodes
196	and
197	.Ar links
198	specifiers are ignored.
199	.It Fl v
200	Be verbose about operations.
201	List filenames as they are written to the archive.
202	.It Fl z
203	Compress archive using
204	.Xr gzip 1
205	format.
206	.It Fl Z
207	Compress archive using
208	.Xr compress 1
209	format.
210	.El
211	.It Fl i
212	Restore files from an archive.
213	Reads the archive file from
214	standard input and extracts files matching the
215	.Ar patterns
216	that were specified on the command line.
217	.Bl -tag -width Ds
218	.It Fl b
219	Do byte and word swapping after reading in data from the
220	archive, for restoring archives created on systems with
221	a different byte order.
222	.It Fl B
223	Set the block size of the archive being read to 5120 bytes.
224	.It Fl c
225	Expect the archive headers to be in ASCII format.
226	.It Fl C Ar bytes
227	Read archive written with a block size of
228	.Ar bytes .
229	.It Fl d
230	Create any intermediate directories as needed during
231	restore.
232	.It Fl E Ar file
233	Read list of file name patterns to extract or list from
234	.Ar file .
235	.It Fl f
236	Restore all files except those matching the
237	.Ar patterns
238	given on the command line.
239	.It Fl F Ar archive
240	.It Fl I Ar archive
241	Use the specified file as the input for the archive.
242	.It Fl H Ar format
243	Read an archive of the specified format.
244	Recognised formats are:
245	.Pp
246	.Bl -tag -width sv4cpio -compact
247	.It Ar bcpio
248	Old binary
249	.Nm
250	format.
251	.It Ar cpio
252	Old octal character
253	.Nm
254	format.
255	.It Ar sv4cpio
256	SVR4 hex
257	.Nm
258	format.
259	.It Ar sv4crc
260	SVR4 hex
261	.Nm
262	format with checksums.
263	.It Ar tar
264	Old tar format.
265	.It Ar ustar
266	POSIX ustar format.
267	.It "\ "
268	.It Ar bin
269	These
270	.It Ar crc
271	four
272	.It Ar newc
273	formats
274	.It Ar odc
275	are supported for backwards compatibility only.
276	.El
277	.It Fl m
278	Restore modification times on files.
279	.It Fl r
280	Rename restored files interactively.
281	.It Fl s
282	Swap bytes after reading data from the archive.
283	.It Fl S
284	Swap words after reading data from the archive.
285	.It Fl t
286	Only list the contents of the archive, no files or
287	directories will be created.
288	.It Fl u
289	Overwrite files even when the file in the archive is
290	older than the one that will be overwritten.
291	.It Fl v
292	Be verbose about operations.
293	List filenames as they are copied in from the archive.
294	.It Fl z
295	Uncompress archive using
296	.Xr gzip 1
297	format.
298	.It Fl Z
299	Uncompress archive using
300	.Xr compress 1
301	format.
302	.It Fl 6
303	Process old-style
304	.Nm
305	format archives.
306	.El
307	.It Fl p
308	Copy files from one location to another in a single pass.
309	The list of files to copy are read from standard input and
310	written out to a directory relative to the specified
311	.Ar directory
312	argument.
313	.Bl -tag -width Ds
314	.It Fl a
315	Reset the access times on files that have been copied.
316	.It Fl d
317	Create any intermediate directories as needed to write
318	the files at the new location.
319	.It Fl l
320	When possible, link files rather than creating an
321	extra copy.
322	.It Fl L
323	Follow symbolic links.
324	.It Fl m
325	Restore modification times on files.
326	.It Fl u
327	Overwrite files even when the original file being copied is
328	older than the one that will be overwritten.
329	.It Fl v
330	Be verbose about operations.
331	List filenames as they are copied.
332	.El
333	.El
334	.Sh ENVIRONMENT
335	.Bl -tag -width Fl
336	.It Ev TMPDIR
337	Path in which to store temporary files.
338	.El
339	.Sh ERRORS
340	.Nm
341	will exit with one of the following values:
342	.Bl -tag -width 2n
343	.It 0
344	All files were processed successfully.
345	.It 1
346	An error occurred.
347	.El
348	.Pp
349	Whenever
350	.Nm
351	cannot create a file or a link when extracting an archive or cannot
352	find a file while writing an archive, or cannot preserve the user
353	ID, group ID, file mode, or access and modification times when the
354	.Fl p
355	option is specified, a diagnostic message is written to standard
356	error and a non-zero exit value will be returned, but processing
357	will continue.
358	In the case where
359	.Nm
360	cannot create a link to a file,
361	.Nm
362	will not create a second copy of the file.
363	.Pp
364	If the extraction of a file from an archive is prematurely terminated
365	by a signal or error,
366	.Nm
367	may have only partially extracted the file the user wanted.
368	Additionally, the file modes of extracted files and directories may
369	have incorrect file bits, and the modification and access times may
370	be wrong.
371	.Pp
372	If the creation of an archive is prematurely terminated by a signal
373	or error,
374	.Nm
375	may have only partially created the archive, which may violate the
376	specific archive format specification.
377	.Sh SEE ALSO
378	.Xr pax 1 ,
379	.Xr tar 1
380	.Sh AUTHORS
381	Keith Muller at the University of California, San Diego.
382	.Sh CAVEATS
383	Different file formats have different maximum file sizes.
384	It is recommended that a format such as cpio or ustar
385	be used for larger files.
386	.Pp
387	.Bl -column "File format" "Maximum file size" -offset indent -compact
388	.It Sy "File format" Ta Sy "Maximum file size"
389	.It bcpio Ta 4 Gibibytes
390	.It sv4cpio Ta 4 Gibibytes
391	.It cpio Ta 8 Gibibytes
392	.It tar Ta 8 Gibibytes
393	.It ustar Ta 8 Gibibytes
394	.El
395	.Sh BUGS
396	The
397	.Fl s
398	and
399	.Fl S
400	options are currently not implemented.
401	.Sh CAVEATS
402	The backwards-compatible format options are not available in the
403	.Xr pax 1
404	front-end.
405	.Pp
406	The
407	.Fl M
408	option is a MirBSD extensions, available starting with
409	.Mx 8 .
410	Archives written using these options are, however, compatible to
411	the standard and should be readable on any other system.
412	The only option whose behaviour is not explicitly allowed by the
413	standard is hard link unification (write file contens only once)
414	selected by
415	.Fl M Ar 0x0002 .