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35 .\" @(#)chmod.1 8.4 (Berkeley) 3/31/94
36 .\" $FreeBSD: src/bin/chmod/chmod.1,v 1.33 2002/10/01 20:32:59 trhodes Exp $
43 .Nd change file modes or Access Control Lists
47 .Op Fl R Op Fl H | L | P
52 .Op Fl R Op Fl H | L | P
58 .Op Fl R Op Fl H | L | P
63 .Op Fl R Op Fl H | L | P
68 .Op Fl R Op Fl H | L | P
74 utility modifies the file mode bits of the listed files
77 operand. It may also be used to modify the Access Control
78 Lists (ACLs) associated with the listed files.
80 The generic options are as follows:
85 option is specified, symbolic links on the command line are followed.
86 (Symbolic links encountered in the tree traversal are not followed by
91 option is specified, all symbolic links are followed.
95 option is specified, no symbolic links are followed.
98 Change the modes of the file hierarchies rooted in the files
99 instead of just the files themselves.
101 Do not display a diagnostic message if
103 could not modify the mode for
108 to be verbose, showing filenames as the mode is modified.
111 flag is specified more than once, the old and new modes of the file
112 will also be printed, in both octal and symbolic notation.
120 options are ignored unless the
123 In addition, these options override each other and the
124 command's actions are determined by the last one specified.
126 Only the owner of a file or the super-user is permitted to change
131 Modes may be absolute or symbolic.
132 An absolute mode is an octal number constructed from the sum of
133 one or more of the following values:
135 .Bl -tag -width 6n -compact -offset indent
137 (the set-user-ID-on-execution bit) Executable files with this bit set
138 will run with effective uid set to the uid of the file owner.
139 Directories with the set-user-id bit set will force all files and
140 sub-directories created in them to be owned by the directory owner
141 and not by the uid of the creating process, if the underlying file
142 system supports this feature: see
149 (the set-group-ID-on-execution bit) Executable files with this bit set
150 will run with effective gid set to the gid of the file owner.
160 Allow write by owner.
162 For files, allow execution by owner.
163 For directories, allow the owner to
164 search in the directory.
166 Allow read by group members.
168 Allow write by group members.
170 For files, allow execution by group members.
171 For directories, allow
172 group members to search in the directory.
174 Allow read by others.
176 Allow write by others.
178 For files, allow execution by others.
179 For directories allow others to
180 search in the directory.
183 For example, the absolute mode that permits read, write and execute by
184 the owner, read and execute by group members, read and execute by
185 others, and no set-uid or set-gid behaviour is 755
186 (400+200+100+040+010+004+001).
188 The symbolic mode is described by the following grammar:
189 .Bd -literal -offset indent
190 mode ::= clause [, clause ...]
191 clause ::= [who ...] [action ...] action
192 action ::= op [perm ...]
193 who ::= a | u | g | o
195 perm ::= r | s | t | w | x | X | u | g | o
200 symbols ``u'', ``g'', and ``o'' specify the user, group, and other parts
201 of the mode bits, respectively.
204 symbol ``a'' is equivalent to ``ugo''.
208 symbols represent the portions of the mode bits as follows:
210 .Bl -tag -width Ds -compact -offset indent
214 The set-user-ID-on-execution and set-group-ID-on-execution bits.
220 The execute/search bits.
222 The execute/search bits if the file is a directory or any of the
223 execute/search bits are set in the original (unmodified) mode.
226 symbol ``X'' are only meaningful in conjunction with the
228 symbol ``+'', and are ignored in all other cases.
230 The user permission bits in the original mode of the file.
232 The group permission bits in the original mode of the file.
234 The other permission bits in the original mode of the file.
239 symbols represent the operation performed, as follows:
242 If no value is supplied for
244 the ``+'' operation has no effect.
245 If no value is supplied for
247 each permission bit specified in
249 for which the corresponding bit in the file mode creation mask
251 Otherwise, the mode bits represented by the specified
257 If no value is supplied for
259 the ``\-'' operation has no effect.
260 If no value is supplied for
262 each permission bit specified in
264 for which the corresponding bit in the file mode creation mask
265 is clear, is cleared.
266 Otherwise, the mode bits represented by the specified
272 The mode bits specified by the
274 value are cleared, or, if no who value is specified, the owner, group
275 and other mode bits are cleared.
276 Then, if no value is supplied for
278 each permission bit specified in
280 for which the corresponding bit in the file mode creation mask
282 Otherwise, the mode bits represented by the specified
291 specifies one or more operations to be performed on the mode
292 bits, and each operation is applied to the mode bits in the
295 Operations upon the other permissions only (specified by the symbol
296 ``o'' by itself), in combination with the
298 symbols ``s'' or ``t'', are ignored.
299 .Sh EXAMPLES OF VALID MODES
300 .Bl -tag -width "u=rwx,go=u-w" -compact
302 make a file readable by anyone and writable by the owner only.
305 deny write permission to group and others.
308 set the read and write permissions to the usual defaults, but
309 retain any execute permissions that are currently set.
312 make a directory or file searchable/executable by everyone if it is
313 already searchable/executable by anyone.
318 make a file readable/executable by everyone and writable by the owner only.
321 clear all mode bits for group and others.
324 set the group bits equal to the user bits, but clear the group write bit.
326 .Sh ACL MANIPULATION OPTIONS
327 ACLs are manipulated using extensions to the symbolic mode
328 grammar. Each file has one ACL, containing an ordered list of entries.
329 Each entry refers to a user or group, and grants or denies a set of
332 The following permissions are applicable to all filesystem objects:
333 .Bl -tag -width 6n -compact -offset indent
335 Delete the item. Deletion may be granted by either this permission
336 on an object or the delete_child right on the containing directory.
338 Read an objects basic attributes. This is implicitly granted if
339 the object can be looked up and not explicitly denied.
341 Write an object's basic attributes.
343 Read extended attributes.
345 Write extended attributes.
347 Read an object's extended security information (ACL).
349 Write an object's security information (ownership, mode, ACL).
351 Change an object's ownership.
354 The following permissions are applicable to directories:
355 .Bl -tag -width 6n -compact -offset indent
359 Look up files by name.
365 Delete a contained object. See the file delete permission above.
368 The following permissions are applicable to non-directory filesystem objects:
369 .Bl -tag -width 6n -compact -offset indent
375 Open for writing, but in a fashion that only allows writes into areas of
376 the file not previously written.
378 Execute the file as a script or program.
381 ACL inheritance is controlled with the following permissions words, which
382 may only be applied to directories:
383 .Bl -tag -width 6n -compact -offset indent
386 .It directory_inherit
387 Inherit to directories.
389 This flag is only relevant to entries inherited by subdirectories; it
390 causes the directory_inherit flag to be cleared in the entry that is
391 inherited, preventing further nested subdirectories from also
392 inheriting the entry.
394 The entry is inherited by created items but not considered when processing
398 The ACL manipulation options are as follows:
401 The +a mode parses a new ACL entry from the next argument on
402 the commandline and inserts it into the canonical location in the
403 ACL. If the supplied entry refers to an identity already listed, the
404 two entries are combined.
408 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
409 # chmod +a "admin allow write" file1
411 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
414 # chmod +a "guest deny read" file1
416 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
420 # chmod +a "admin allow delete" file1
422 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
425 2: admin allow write,delete
427 The +a mode strives to maintain correct canonical form for the ACL.
433 By default, chmod adds entries to the top of the local deny and local
434 allow lists. Inherited entries are added by using the +ai mode.
438 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
441 2: admin allow write,delete
442 3: juser inherited deny delete
443 4: admin inherited allow delete
444 5: backup inherited deny read
445 6: admin inherited allow write-security
446 # chmod +ai "others allow write" file1
448 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
451 2: admin allow write,delete
452 3: juser inherited deny delete
453 4: others inherited allow read
454 5: admin inherited allow delete
455 6: backup inherited deny read
456 7: admin inherited allow write-security
458 When a specific ordering is required, the exact location at which an
459 entry will be inserted is specified with the +a# mode.
463 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
467 # chmod +a# 2 "others deny read" file1
469 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
475 The +ai# mode may be used to insert inherited entries at a specific
476 location. Note that these modes allow non-canonical ACL ordering to
479 The -a mode is used to delete ACL entries. All entries exactly
480 matching the supplied entry will be deleted. If the entry lists a
481 subset of rights granted by an entry, only the rights listed are
482 removed. Entries may also be deleted by index using the -a# mode.
486 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
489 2: admin allow write,delete
492 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
494 1: admin allow write,delete
495 # chmod -a "admin allow write" file1
497 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
499 1: admin allow delete
501 Inheritance is not considered when processing the -a mode; rights and
502 entries will be removed regardless of their inherited state.
504 Individual entries are rewritten using the =a# mode.
508 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
510 1: admin allow delete
511 # chmod =a# 1 "admin allow write,chown"
513 -rw-r--r--+ 1 juser wheel 0 Apr 28 14:06 file1
515 1: admin allow write,chown
517 This mode may not be used to add new entries.
519 Reads the ACL information from stdin, as a sequential list
520 of ACEs, separated by newlines. If the information parses correctly,
521 the existing information is replaced.
523 Returns false if any of the named files have ACLs in non-canonical order.
525 Removes the 'inherited' bit from all entries in the named file(s) ACLs.
527 Removes all inherited entries from the named file(s) ACL(s).
529 Removes the ACL from the named file(s).
534 option is non-standard and its use in scripts is not recommended.
550 utility is expected to be
552 compatible with the exception of the
556 which is not included in that standard.