noxz.tech/software/acst/index.www
1acst as a tool is designed to detect silent data corruption by first writing
2the mtime and the SHA256 checksum of a file into its extended attributes and
3then, upon later execution, comparing and verifying changes against both the
4mtime and checksum.
5
6.HnS 1
7Download
8.HnE
9
10.URL //noxz.tech/git/acst.git/archive/acst-0.1.4.tar.gz "acst 0.1.4"
11(30kb) (2023-03-09)
12
13.HnS 1
14Manual
15.HnE
16
17.CDS
18.COS
19ACST(1) General Commands Manual ACST(1)
20
21NAME
22 acst - Actual C-implementation of a Simple shaTag
23
24SYNOPSIS
25 acst [-dhmnqvx] <FILE...>
26
27DESCRIPTION
28 acst is a minimal and simplified implementation in C of, or rather,
29 inspired by, shatag and also inspired by cshatag.
30
31 acst as a tool is designed to detect silent data corruption by first
32 writing the mtime and the SHA256 checksum of a file into its extended
33 attributes and then, upon later execution, comparing and verifying
34 changes against both the mtime and checksum. For this to work, the file
35 system intended to be verified must first support extended user
36 attributes, either by being mounted with user_xattr enabled or by other
37 means. Depending on how these variables differ, various file statuses
38 are being reported (see the FILE STATUSES section).
39
40 acst won't follow symlinks due to the risks of creating reference loops
41 or referencing data outside of the indented scope of subdirectories.
42 acst also won't descend into directories on other file systems than the
43 one specified using the FILE argument. Keep in mind that if multiple
44 files with different file systems are specified using the FILE
45 argument, they will get traversed indifferent of each other. For
46 example, if you specify two different partitions mounted on two
47 different directories, they would both be traversed.
48
49 acst reads names of files to open from standard input if the only FILE
50 argument is '-'. To open files starting with '-', use '--' to cancel
51 parsing of arguments.
52
53 acst does not aim to be format-compatible with shatag and uses
54 different names for the extended attributes but similar formats for the
55 extended attributes (see the COMPATIBILITY section).
56
57OPTIONS
58 -d Check for duplicates among files based on stored checksums from
59 acst's extended attributes. Return values when checking for
60 duplicates are normally 0 for success or 1 for fatal errors (in
61 other words, the RETURN VALUES section does not apply).
62 Certainty of the result is, of course, dependent on checksums
63 being created or corrected fairly recently as no checksums are
64 being computed during the duplicate check.
65
66 -h Print brief usage information to standard output and exit.
67
68 -m Summarize information at end of execution.
69
70 -n Don't create or update any extended file attributes. File
71 hashing and checking will be performed, but no extended file
72 attributes will be created or updated.
73
74 -q Quiet mode. If specified one time ok files are not being
75 reported. If specified two times, only corrupt, backdated, and
76 malformed files and errors are being reported.
77
78 -x Remove acts's extended attributes (xattrs) from FILE.
79
80 -v prints version information to stderr, then exits.
81
82RETURN VALUES
83 0 Success
84
85 1 Wrong number of or invalid arguments.
86
87 2 One or more files, including directories when executed with the
88 recursive flag, could not be opened.
89
90 3 One or more files is not a regular file and probably a symlink
91 of sorts.
92
93 4 Extended attributes could not be written to one or more files.
94
95 5 At least one file was found to be corrupt, backdated or
96 malformed.
97
98 6 More than one type of error has occurred.
99
100FILE STATUSES
101 During program execution and processing of each file various file
102 statuses will appear on stdout. Following are descriptions of these
103 statuses.
104
105 ok Checksum is correct and mtime is unchanged.
106
107 hash ok
108 Checksum is correct and mtime was changed.
109
110 outdated
111 Checksum is incorrect and mtime is newer than the one stored as
112 an extended Attribute.
113
114 backdated
115 Checksum is incorrect and mtime is older than the one stored as
116 an extended Attribute.
117
118 malformed
119 Extended attributes could not be read as otherwise intended.
120
121 corrupt
122 Checksum is incorrect but mtime stayed the same.
123
124 disrupted
125 File was modified during hash computation.
126
127 new Extended attributes are missing and were added.
128
129 xattr removed
130 Extended attributes were removed.
131
132 dup Duplicate of checksum among files checked.
133
134EXAMPLES
135 find /mnt/memorystick -xdev -type f | acst - > /root/acst.log
136 will use find to recursively traverse through files in
137 /mnt/memorystick within the same file system and log the result
138 to /root/acst.log.
139
140 find /home/user01 /strg/shr/media -type f | acst - > /root/acst.log
141 will recursively process files in both /home/user01 and
142 /mnt/memorystick even if they belong to different file systems,
143 and then log the result to /root/acst.log.
144
145 find /home/user01 /strg/shr/media -type f | acst -m - > /root/acst.log
146 will perform the same operation as above with the addition of
147 also summarizing the result of the execution to the log.
148
149 find /mnt/memorystick -xdev -type f | acst -x - > /root/acst.log
150 will recursively process and remove extended attributes from
151 files in /mnt/memorystick and log the result to /root/acst.log.
152
153 find /mnt/memorystick -xdev -type f | acst -d -
154 will recursively check for duplicates among files in
155 /mnt/memorystick based on checksums stored as extended
156 attributes.
157
158COMPATIBILITY
159 acst writes to user.acst.cs and user.acst.ts instead of the
160 user.shatag.sha256 and user.shatag.ts specified by shatag.
161 acst writes the user.acst.ts field with full integer nanosecond
162 precision, while python-implemented shatag doesn't.
163
164AUTHOR
165 Chris Noxz <chris@noxz.tech>
166
167COPYRIGHT
168 Copyright © 2022 Chris Noxz.
169
170 License: GPLv3+
171
172 GNU GPL version 3 or later
173 <https://www.gnu.org/licenses/licenses.html>.
174
175 This is free software: you are free to change and redistribute it.
176 There is NO WARRANTY, to the extent permitted by law.
177
178SEE ALSO
179 shatag(1), cshatag(1), sha256sum(1), getfattr(1), setfattr(1)
180
181 The original shatag utility, written in python by Maxime Augier:
182 https://bitbucket.org/maugier/shatag
183 and cshatag utility, written in Go by Jakob Unterwurzacher:
184 https://github.com/rfjakob/cshatag
185
186AVAILABILITY
187 Up-to-date sources can be found at:
188 https://noxz.tech/git/acst
189 https://noxz.tech/software/acst
190
191 acst-0.1.4 ACST(1)
192.COE
193.CDE
194
195.HnS 1
196Installation
197.HnE
198
199Edit config.mk to match your local setup (acst is installed into the
200.I /usr/local
201namespace by default), then simply enter the following command to install (if
202necessary as root):
203
204.CDS
205.COS
206make clean install
207.COE
208.CDE
209
210get source
211.URL //noxz.tech/git/acst.git here .
