summaryrefslogtreecommitdiffstats
path: root/manpages/mksquashfs.1
blob: 47377f4df7fa29a3f61e2121a4c94d8fc6eea7e1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
.\" DO NOT MODIFY THIS FILE!  It was generated by help2man 1.48.5.
.TH MKSQUASHFS "1" "March 2023" "mksquashfs version 4.6.1" "User Commands"
.SH NAME
mksquashfs - tool to create and append to squashfs filesystems
.SH SYNOPSIS
.B mksquashfs
\fI\,source1 source2 \/\fR...  \fI\,FILESYSTEM \/\fR[\fI\,OPTIONS\/\fR] [\fI\,-e list of exclude dirs/files\/\fR]
.SH DESCRIPTION
Squashfs is a highly compressed read-only filesystem for Linux.
It uses either gzip/xz/lzo/lz4/zstd compression to compress both files, inodes
and directories.  Inodes in the system are very small and all blocks are
packed to minimise data overhead. Block sizes greater than 4K are supported
up to a maximum of 1Mbytes (default block size 128K).

Squashfs is intended for general read-only filesystem use, for archival
use (i.e. in cases where a .tar.gz file may be used), and in constrained
block device/memory systems (e.g. embedded systems) where low overhead is
needed.
.SH OPTIONS
.SS "Filesystem compression options:"
.TP
\fB\-b\fR BLOCK_SIZE
set data block to BLOCK_SIZE.  Default 128 Kbytes. Optionally a suffix of K or M can be given to specify Kbytes or Mbytes respectively.
.TP
\fB\-comp\fR COMP
select COMP compression. Compressors available: gzip (default), lzo, lz4, xz, zstd.
.TP
\fB\-noI\fR
do not compress inode table.
.TP
\fB\-noId\fR
do not compress the uid/gid table (implied by \fB\-noI\fR).
.TP
\fB\-noD\fR
do not compress data blocks.
.TP
\fB\-noF\fR
do not compress fragment blocks.
.TP
\fB\-noX\fR
do not compress extended attributes.
.TP
\fB\-no\-compression\fR
do not compress any of the data or metadata.  This is equivalent to specifying \fB\-noI\fR \fB\-noD\fR \fB\-noF\fR and \fB\-noX\fR.
.SS "Filesystem build options:"
.TP
\fB\-tar\fR
read uncompressed tar file from standard in (stdin).
.TP
\fB\-no\-strip\fR
act like tar, and do not strip leading directories from source files.
.TP
\fB\-tarstyle\fR
alternative name for \fB\-no\-strip\fR.
.TP
\fB\-cpiostyle\fR
act like cpio, and read file pathnames from standard in (stdin).
.TP
\fB\-cpiostyle0\fR
like \fB\-cpiostyle\fR, but filenames are null terminated.  Can be used with find \fB\-print0\fR action.
.TP
\fB\-reproducible\fR
build filesystems that are reproducible (default).
.TP
\fB\-not\-reproducible\fR
build filesystems that are not reproducible.
.TP
\fB\-mkfs\-time\fR TIME
set filesystem creation timestamp to TIME. TIME can be an unsigned 32\-bit int indicating seconds since the epoch (1970\-01\-01) or a string value which is passed to the "date" command to parse. Any string value which the date command recognises can be used such as "now", "last week", or "Wed Feb 15 21:02:39 GMT 2023".
.TP
\fB\-all\-time\fR TIME
set all file timestamps to TIME. TIME can be an unsigned 32\-bit int indicating seconds since the epoch (1970\-01\-01) or a string value which is passed to the "date" command to parse. Any string value which the date command recognises can be used such as "now", "last week", or "Wed Feb 15 21:02:39 GMT 2023".
.TP
\fB\-root\-time\fR TIME
set root directory time to TIME. TIME can be an unsigned 32\-bit int indicating seconds since the epoch (1970\-01\-01) or a string value which is passed to the "date" command to parse. Any string value which the date command recognises can be used such as "now", "last week", or "Wed Feb 15 21:02:39 GMT 2023".
.TP
\fB\-root\-mode\fR MODE
set root directory permissions to octal MODE.
.TP
\fB\-root\-uid\fR VALUE
set root directory owner to specified VALUE, VALUE can be either an integer uid or user name.
.TP
\fB\-root\-gid\fR VALUE
set root directory group to specified VALUE, VALUE can be either an integer gid or group name.
.TP
\fB\-all\-root\fR
make all files owned by root.
.TP
\fB\-force\-uid\fR VALUE
set all file uids to specified VALUE, VALUE can be either an integer uid or user name.
.TP
\fB\-force\-gid\fR VALUE
set all file gids to specified VALUE, VALUE can be either an integer gid or group name.
.TP
\fB\-pseudo\-override\fR
make pseudo file uids and gids override \fB\-all\-root\fR, \fB\-force\-uid\fR and \fB\-force\-gid\fR options.
.TP
\fB\-no\-exports\fR
do not make filesystem exportable via NFS (\fB\-tar\fR default).
.TP
\fB\-exports\fR
make filesystem exportable via NFS (default).
.TP
\fB\-no\-sparse\fR
do not detect sparse files.
.TP
\fB\-no\-tailends\fR
do not pack tail ends into fragments (default).
.TP
\fB\-tailends\fR
pack tail ends into fragments.
.TP
\fB\-no\-fragments\fR
do not use fragments.
.TP
\fB\-no\-duplicates\fR
do not perform duplicate checking.
.TP
\fB\-no\-hardlinks\fR
do not hardlink files, instead store duplicates.
.TP
\fB\-keep\-as\-directory\fR
if one source directory is specified, create a root directory containing that directory, rather than the contents of the directory.
.SS "Filesystem filter options:"
.TP
\fB\-p\fR PSEUDO\-DEFINITION
add pseudo file definition.  The definition should be quoted.
.TP
\fB\-pf\fR PSEUDO\-FILE
add list of pseudo file definitions from PSEUDO\-FILE, use \- for stdin.  Pseudo file definitions should not be quoted.
.TP
\fB\-sort\fR SORT_FILE
sort files according to priorities in SORT_FILE.  One file or dir with priority per line.  Priority \fB\-32768\fR to 32767, default priority 0.
.TP
\fB\-ef\fR EXCLUDE_FILE
list of exclude dirs/files.  One per line.
.TP
\fB\-wildcards\fR
allow extended shell wildcards (globbing) to be used in exclude dirs/files.
.TP
\fB\-regex\fR
allow POSIX regular expressions to be used in exclude dirs/files.
.TP
\fB\-max\-depth\fR LEVELS
descend at most LEVELS of directories when scanning filesystem.
.TP
\fB\-one\-file\-system\fR
do not cross filesystem boundaries.  If a directory crosses the boundary, create an empty directory for each mount point.  If a file crosses the boundary ignore it.
.TP
\fB\-one\-file\-system\-x\fR
do not cross filesystem boundaries. Like \fB\-one\-file\-system\fR option except directories are also ignored if they cross the boundary.
.SS "Filesystem extended attribute (xattrs) options:"
.TP
\fB\-no\-xattrs\fR
do not store extended attributes.
.TP
\fB\-xattrs\fR
store extended attributes (default).
.TP
\fB\-xattrs\-exclude\fR REGEX
exclude any xattr names matching REGEX.  REGEX is a POSIX regular expression, e.g. \fB\-xattrs\-exclude\fR '^user.' excludes xattrs from the user namespace.
.TP
\fB\-xattrs\-include\fR REGEX
include any xattr names matching REGEX.  REGEX is a POSIX regular expression, e.g. \fB\-xattrs\-include\fR '^user.' includes xattrs from the user namespace.
.TP
\fB\-xattrs\-add\fR NAME=VAL
add the xattr NAME with VAL to files.  If an user xattr it will be added to regular files and directories (see man 7 xattr).  Otherwise it will be added to all files.  VAL by default will be treated as binary (i.e. an uninterpreted byte sequence), but it can be prefixed with 0s, where it will be treated as base64 encoded, or prefixed with 0x, where val will be treated as hexidecimal.  Additionally it can be prefixed with 0t where this encoding is similar to binary encoding, except backslashes are specially treated, and a backslash followed by 3 octal digits can be used to encode any ASCII character, which obviously can be used to encode control codes.  The option can be repeated multiple times to add multiple xattrs.
.SS "Mksquashfs runtime options:"
.TP
\fB\-version\fR
print version, licence and copyright message.
.TP
\fB\-exit\-on\-error\fR
treat normally ignored errors as fatal.
.TP
\fB\-quiet\fR
no verbose output.
.TP
\fB\-info\fR
print files written to filesystem.
.TP
\fB\-no\-progress\fR
do not display the progress bar.
.TP
\fB\-progress\fR
display progress bar when using the \fB\-info\fR option.
.TP
\fB\-percentage\fR
display a percentage rather than the full progress bar. Can be used with dialog \fB\-\-gauge\fR etc.
.TP
\fB\-throttle\fR PERCENTAGE
throttle the I/O input rate by the given percentage. This can be used to reduce the I/O and CPU consumption of Mksquashfs.
.TP
\fB\-limit\fR PERCENTAGE
limit the I/O input rate to the given percentage. This can be used to reduce the I/O and CPU consumption of Mksquashfs (alternative to \fB\-throttle\fR).
.TP
\fB\-processors\fR NUMBER
use NUMBER processors.  By default will use number of processors available.
.TP
\fB\-mem\fR SIZE
use SIZE physical memory for caches.  Use K, M or G to specify Kbytes, Mbytes or Gbytes respectively.
.TP
\fB\-mem\-percent\fR PERCENT
use PERCENT physical memory for caches.  Default 25%.
.TP
\fB\-mem\-default\fR
print default memory usage in Mbytes.
.SS "Filesystem append options:"
.TP
\fB\-noappend\fR
do not append to existing filesystem.
.TP
\fB\-root\-becomes\fR NAME
when appending source files/directories, make the original root become a subdirectory in the new root called NAME, rather than adding the new source items to the original root.
.TP
\fB\-no\-recovery\fR
do not generate a recovery file.
.TP
\fB\-recovery\-path\fR NAME
use NAME as the directory to store the recovery file.
.TP
\fB\-recover\fR NAME
recover filesystem data using recovery file NAME.
.SS "Filesystem actions options:"
.TP
\fB\-action\fR ACTION@EXPRESSION
evaluate EXPRESSION on every file, and execute ACTION if it returns TRUE.
.TP
\fB\-log\-action\fR ACTION@EXPRESSION
as above, but log expression evaluation results and actions performed.
.TP
\fB\-true\-action\fR ACTION@EXPRESSION
as above, but only log expressions which return TRUE.
.TP
\fB\-false\-action\fR ACTION@EXPRESSION
as above, but only log expressions which return FALSE.
.TP
\fB\-action\-file\fR FILE
as action, but read actions from FILE.
.TP
\fB\-log\-action\-file\fR FILE
as \fB\-log\-action\fR, but read actions from FILE.
.TP
\fB\-true\-action\-file\fR FILE
as \fB\-true\-action\fR, but read actions from FILE.
.TP
\fB\-false\-action\-file\fR FILE
as \fB\-false\-action\fR, but read actions from FILE.
.SS "Tar file only options:"
.TP
\fB\-default\-mode\fR MODE
tar files often do not store permissions for intermediate directories.  This option sets the default directory permissions to octal MODE, rather than 0755. This also sets the root inode mode.
.TP
\fB\-default\-uid\fR UID
tar files often do not store uids for intermediate directories.  This option sets the default directory owner to UID, rather than the user running Mksquashfs. This also sets the root inode uid.
.TP
\fB\-default\-gid\fR GID
tar files often do not store gids for intermediate directories.  This option sets the default directory group to GID, rather than the group of the user running Mksquashfs.  This also sets the root inode gid.
.TP
\fB\-ignore\-zeros\fR
allow tar files to be concatenated together and fed to Mksquashfs.  Normally a tarfile has two consecutive 512 byte blocks filled with zeros which means EOF and Mksquashfs will stop reading after the first tar file on encountering them. This option makes Mksquashfs ignore the zero filled blocks.
.SS "Expert options (these may make the filesystem unmountable):"
.TP
\fB\-nopad\fR
do not pad filesystem to a multiple of 4K.
.TP
\fB\-offset\fR OFFSET
skip OFFSET bytes at the beginning of FILESYSTEM. Optionally a suffix of K, M or G can be given to specify Kbytes, Mbytes or Gbytes respectively. Default 0 bytes.
.TP
\fB\-o\fR OFFSET
synonym for \fB\-offset\fR.
.SS "Miscellaneous options:"
.TP
\fB\-fstime\fR TIME
alternative name for \fB\-mkfs\-time\fR.
.TP
\fB\-always\-use\-fragments\fR
alternative name for \fB\-tailends\fR.
.TP
\fB\-root\-owned\fR
alternative name for \fB\-all\-root\fR.
.TP
\fB\-noInodeCompression\fR
alternative name for \fB\-noI\fR.
.TP
\fB\-noIdTableCompression\fR
alternative name for \fB\-noId\fR.
.TP
\fB\-noDataCompression\fR
alternative name for \fB\-noD\fR.
.TP
\fB\-noFragmentCompression\fR
alternative name for \fB\-noF\fR.
.TP
\fB\-noXattrCompression\fR
alternative name for \fB\-noX\fR.
.TP
\fB\-help\fR
output this options text to stdout.
.TP
\fB\-h\fR
output this options text to stdout.
.TP
\fB\-Xhelp\fR
print compressor options for selected compressor.
.SH "PSEUDO FILE DEFINITION FORMAT"
.TP
\fB\-p\fR "filename d mode uid gid"
create a directory.
.TP
\fB\-p\fR "filename m mode uid gid"
modify filename.
.TP
\fB\-p\fR "filename b mode uid gid major minor"
create a block device.
.TP
\fB\-p\fR "filename c mode uid gid major minor"
create a character device.
.TP
\fB\-p\fR "filename f mode uid gid command"
create file from stdout of command.
.TP
\fB\-p\fR "filename s mode uid gid symlink"
create a symbolic link.
.TP
\fB\-p\fR "filename i mode uid gid [s|f]"
create a socket (s) or FIFO (f).
.TP
\fB\-p\fR "filename x name=val"
create an extended attribute.
.TP
\fB\-p\fR "filename l linkname"
create a hard\-link to linkname.
.TP
\fB\-p\fR "filename L pseudo_filename"
same, but link to pseudo file.
.TP
\fB\-p\fR "filename D time mode uid gid"
create a directory with timestamp time.
.TP
\fB\-p\fR "filename M time mode uid gid"
modify a file with timestamp time.
.TP
\fB\-p\fR "filename B time mode uid gid major minor"
create block device with timestamp time.
.TP
\fB\-p\fR "filename C time mode uid gid major minor"
create char device with timestamp time.
.TP
\fB\-p\fR "filename F time mode uid gid command"
create file with timestamp time.
.TP
\fB\-p\fR "filename S time mode uid gid symlink"
create symlink with timestamp time.
.TP
\fB\-p\fR "filename I time mode uid gid [s|f]"
create socket/fifo with timestamp time.
.SH "COMPRESSORS AVAILABLE AND COMPRESSOR SPECIFIC OPTIONS"
.SS "gzip (default):"
.TP
\fB\-Xcompression\-level\fR COMPRESSION\-LEVEL
COMPRESSION\-LEVEL should be 1 .. 9 (default 9).
.TP
\fB\-Xwindow\-size\fR WINDOW\-SIZE
WINDOW\-SIZE should be 8 .. 15 (default 15).
.TP
\fB\-Xstrategy\fR strategy1,strategy2,...,strategyN
Compress using strategy1,strategy2,...,strategyN in turn and choose the best compression. Available strategies: default, filtered, huffman_only, run_length_encoded and fixed.
.SS "lzo:"
.TP
\fB\-Xalgorithm\fR ALGORITHM
Where ALGORITHM is one of: lzo1x_1, lzo1x_1_11, lzo1x_1_12, lzo1x_1_15, lzo1x_999 (default).
.TP
\fB\-Xcompression\-level\fR COMPRESSION\-LEVEL
COMPRESSION\-LEVEL should be 1 .. 9 (default 8) Only applies to lzo1x_999 algorithm.
.SS "lz4:"
.TP
\fB\-Xhc\fR
Compress using LZ4 High Compression.
.SS "xz:"
.TP
\fB\-Xbcj\fR filter1,filter2,...,filterN
Compress using filter1,filter2,...,filterN in turn (in addition to no filter), and choose the best compression. Available filters: x86, arm, armthumb, powerpc, sparc, ia64.
.TP
\fB\-Xdict\-size\fR DICT\-SIZE
Use DICT\-SIZE as the XZ dictionary size.  The dictionary size can be specified as a percentage of the block size, or as an absolute value.  The dictionary size must be less than or equal to the block size and 8192 bytes or larger.  It must also be storable in the xz header as either 2^n or as 2^n+2^(n+1). Example dict\-sizes are 75%, 50%, 37.5%, 25%, or 32K, 16K, 8K etc.
.SS "zstd:"
.TP
\fB\-Xcompression\-level\fR COMPRESSION\-LEVEL
COMPRESSION\-LEVEL should be 1 .. 22 (default 15).
.SH ENVIRONMENT
.TP
SOURCE_DATE_EPOCH
If set, this is used as the filesystem creation timestamp.  Also any file timestamps which are after SOURCE_DATE_EPOCH will be clamped to SOURCE_DATE_EPOCH.  See https://reproducible\-builds.org/docs/source\-date\-epoch/ for more information.
.SH EXAMPLES
.TP
mksquashfs DIRECTORY IMAGE.SQFS
Create a Squashfs filesystem from the contents of DIRECTORY, writing the output
to IMAGE.SQSH.  Mksquashfs will use the default compressor (normally gzip), and
block size of 128 Kbytes.
.TP
mksquashfs DIRECTORY FILE1 FILE2 IMAGE.SQFS
Create a Squashfs filesystem containing DIRECTORY and FILE1 and FILE2.  If
multiple sources are specified on the command line they will be combined into
a single directory.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -b 1M -comp zstd
Use a block size of 1 Mbyte and Zstandard compression to create the filesystem. 
.TP
mksquashfs DIRECTORY IMAGE.SQFS -e file1 file2
Exclude file1 and file2 from DIRECTORY when creating filesystem.  No wildcard
matching of files.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -wildcards -e "*.gz"
Exclude anything in DIRECTORY which matches the wildcard pattern "*.gz".
.TP
mksquashfs DIRECTORY IMAGE.SQFS -wildcards -e "... *.gz"
Exclude files which match the wildcard pattern "*.gz" anywhere within DIRECTORY
and its sub-directories.  The initial "..." indicates the wildcard pattern is
"non-anchored" and will match anywhere.
.PP
Note: when passing wildcarded names to Mksquashfs, they should be quoted (as in
the above examples), to ensure that they are not processed by the shell.

.SS Using pseudo file definitions
.TP
mksquashfs DIRECTORY IMAGE.SQFS -p "build_dir d 0644 0 0"
Create a directory called "build_dir" in the output filesystem.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -p "version.txt l /tmp/build/version"
Create a reference called "version.txt" to a file outside DIRECTORY, which acts
as if the file "/tmp/build/version" was copied or hard-linked into DIRECTORY
before calling Mksquashfs.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -p "date.txt f 0644 0 0 date"
Create a file called "date.txt" which holds the output (stdout) from running
the "date" command.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -p "\\"hello world\\" f 0644 0 0 date"
As above, but, showing that filenames can have spaces, if they are quoted.
The quotes need to be blackslashed to protect them from the shell.
.TP
mksquashfs - IMAGE.SQFS -p "input f 0644 root root dd if=/dev/sda1 bs=1024" -p "/ d 0644 0 0"
Create a file containing the contents of partition /dev/sda1".  Ordinarily
Mksquashfs given a device, fifo, or named socket will place that special file
within the Squashfs filesystem, the above allows input from these special files
to be captured and placed in the Squashfs filesystem.   Note there are no other
sources than the pseudo file, and so the command line source is "-".  If there
are no other sources than pseudo files, the root (/) directory must be defined
too, as seen in this example.
.TP
unsquashfs -pf - IMAGE.SQFS | mksquashfs - NEW.SQFS -pf -
Transcode IMAGE.SQFS to NEW.SQFS by piping the pseudo file output from
Unsquashfs to Mksquashfs using stdout and stdin.  This can convert from
earlier Squashfs filesystems or change compression algorithm, block size etc.
without needing to unpack into an intermediate directory or file.
.PP
Note: pseudo file definitions should be quoted (as in the above examples), to
ensure that they are passed to Mksquashfs as a single argument, and to ensure
that they are not processed by the shell.

.SS Using extended attribute options
.TP
mksquashfs DIRECTORY IMAGE.SQFS -no-xattrs
Do not store any extended attributes in the Squashfs filesystem.  Any extended
attributes in the source files will be ignored.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -xattrs-include "^user."
Filter the extended attributes in the source files, and only store extended
attributes in the user namespace in the Squashfs filesystem.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -xattrs-exclude "^user."
Filter the extended attributes in the source files, and don't store any
extended attributes in the user namespace in the Squashfs filesystem.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -xattrs-add "user.comment=hello world"
Add the extended attribute called "user.comment" with the content "hello world"
to all files and directories in the Squashfs filesystem.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -xattrs-add "user.comment=0thello world\\012"
Add the extended attribute called "user.comment" to all files and directories,
but in this case the contents of the extended attribute will be "hello world"
with a trailing newline character (012 octal).
.TP
mksquashfs DIRECTORY IMAGE.SQFS -xattrs-add "user.comment=0saGVsbG8gd29ybGQ="
Add the extended attribute called "user.comment" to all files and directories,
where the value is given in base64 encoding, representing "hello world".
.TP
mksquashfs DIRECTORY IMAGE.SQFS -action "-xattrs-include(^user.) @ type(f)"
Filter the extended attributes but only in regular files (type f), and only
store extended attributes in the user namespace.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -p "hello_world x user.comment=0tsalve mundi\\012"
Add the extended attribute called "user.comment" to the file called
"hello_world", with the contents of the extended attribute being "salve mundi"
with a trailing newline character (012 octal).

.SS Using Actions to not compress, change attributes etc.
.TP
mksquashfs DIRECTORY IMAGE.SQSH -action "uncompressed @ (name(*.jpg) || name(*.mpg) ) || (name(*.img) && filesize(+1G))"
Specify that any files matching the wildcards "*.jpg" and "*.mpg" should not be
compressed.  Additionally, it also specifies any files matching the wildcard
"*.img" and are larger than 1 Gigabyte should be uncompressed too.  This shows
test operators can be combined with logical expressions.
.TP
mksquashfs DIRECTORY IMAGE.SQSH -action "chmod(o+r)@! perm(o+r)"
If any files within DIRECTORY are not readable by "others", then make them
readable by others in the Squashfs filesystem.
.TP
mksquashfs DIRECTORY IMAGE.SQSH -action "uid(phillip)@! perm(o+r)"
As previous, match on any files which are not readable by "others", but, in
this case change the owner of the file to "phillip" in the Squashfs filesystem.
.TP
mksquashfs DIRECTORY IMAGE.SQSH -action "prune @ type(l) && ! exists"
Delete any symbolic link within DIRECTORY which points outside of DIRECTORY,
i.e. will be unresolvable in the Squashfs filesystem.
.TP
mksquashfs DIRECTORY IMAGE.SQSH -action "exclude @ depth(3)"
Create a Squashfs filesystem containing the two top most levels (contents of
DIRECTORY and immediate sub-directories), and exclude anything at level 3 or
below.
.TP
mksquashfs DIRECTORY IMAGE.SQFS -action "-xattrs-include(^user.) @ type(f)"
Filter the extended attributes but only in regular files (type f), and only
store extended attributes in the user namespace.
.PP
Note: actions should be quoted (as in the above examples), to ensure that they
are passed to Mksquashfs as a single argument, and to ensure that they are not
processed by the shell.
.SH AUTHOR
Written by Phillip Lougher <phillip@squashfs.org.uk>
.SH COPYRIGHT
Copyright \(co 2023 Phillip Lougher <phillip@squashfs.org.uk>
.PP
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2,
or (at your option) any later version.
.PP
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
.SH "SEE ALSO"
unsquashfs(1), sqfstar(1), sqfscat(1)
.PP
The README for the Squashfs\-tools 4.6.1 release, describing the new features can be
read here https://github.com/plougher/squashfs\-tools/blob/master/README\-4.6.1
.PP
The Squashfs\-tools USAGE guide can be read here
https://github.com/plougher/squashfs\-tools/blob/master/USAGE\-4.6
.PP
The ACTIONS\-README file describing how to use the new actions feature can be
read here https://github.com/plougher/squashfs\-tools/blob/master/ACTIONS\-README