1FASTRM(1) InterNetNews Documentation FASTRM(1)
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6 fastrm - Quickly remove a list of files
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9 fastrm [-de] [-c|-cI] [-s|-sM] [-u|-uN] base-directory
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12 fastrm reads a list of either file names or storage API tokens, one per
13 line, from its standard input and removes them. Storage API tokens are
14 removed via the SMcancel() interface. fastrm does not delete files
15 safely or with an eye to security, but rather cuts every corner it can
16 to delete files as fast as it can. It should therefore never be run on
17 publically writable directories, or in any other environment where a
18 hostile party may control the directory structure in which it is
19 working.
20 If a file name is not an absolute path name, it is considered to be
22 relative to base-directory as given on the command line. The base-
23 directory parameter must be a simple absolute pathname (it must not
24 contain multiple consecutive slashes or references to the special
25 directories "." or "..").
26 fastrm is designed to be faster than the typical "| xargs rm" pipeline
28 when given a sorted list of file names as input. For example, fastrm
29 will usually chdir(2) into a directory before removing files from it,
30 meaning that if its input is sorted, most names passed to unlink(2)
31 will be simple names. This can substantially reduce the operating
32 system overhead from directory lookups.
33 fastrm assumes that its input is valid and that it is safe to call
35 unlink(2) on every file name it is given. As a safety measure,
36 however, fastrm when running as root will check with stat(2) that a
37 file name doesn't specify a directory before removing it. (In some
38 operating systems, root is allowed to unlink directories, even
39 directories which aren't empty, which can cause file system
40 corruption.)
41 The input to fastrm should always be sorted -- or even better be in the
43 order file names are output by find(1) -- if speed is an issue and the
44 input isn't solely storage API tokens. (It deals fine with unsorted
45 input, but is unlikely to be any faster in that case than a simple "|
46 xargs rm" command.) Sorting may even slightly speed up the removal of
47 storage API tokens due to caching effects, since sorting will tend to
48 keep all of the tokens from a particular storage method together.
49 Various additional optimizations for removing files can be turned on
51 and/or tuned with options (see below). Which options will be most
52 effective depends heavily on the underlying structure of the file
53 system, the way in which directories are stored and searched, and
54 similar, often underdocumented, operating system implementation
55 details. The more sophisticated the underlying operating system and
56 file system, the more likely that it will already perform the
57 equivalent of these optimizations internally.
58
60 -c[I]
61 Controls when fastrm calls chdir(2). If the number of files to be
62 unlinked from a given directory is at least I, then fastrm will
63 change to that directory before unlinking those files. Otherwise,
64 it will use either the absolute path names or a path name relative
65 to the current directory (whichever is likely more efficient). The
66 I parameter is optional; if just -c is given, -c1 is assumed, which
67 will cause fastrm to always chdir before calling unlink(2). The
68 default is -c3. Use -c0 to prevent fastrm from ever using
69 chdir(2).
70 -d Don't remove any files. Instead, print a list of the files that
72 would be removed to standard output. Each line contains either the
73 current directory of fastrm at the time it would do the unlink and
74 the relative path name it would pass to unlink(2) as two fields
75 separated by whitespace and a "/", the absolute path name (as a
76 single field) that would be passed to unlink(2), or the string
77 "Token" and the storage API token that would be removed.
78 -e Treat an empty input file as an error. This is most useful when
80 fastrm is last in a pipeline after a preceding sort(1) command,
81 ensuring that fastrm will fail if the sort fails.
82 -s[M]
84 When -s is given and the number of files to remove in a directory
85 is greater than M, rather than remove files in the order given,
86 fastrm will open the directory and read it, unlinking files in the
87 order that they appear in the directory. On systems with a per-
88 process directory cache or that use a linear search to find files
89 in a directory, this should make directory lookups faster. The M
90 parameter is optional; if just -s is given, -s5 is assumed.
91 When this option is in effect, fastrm won't attempt to remove files
93 that it doesn't see in the directory, possibly significantly
94 speeding it up if most of the files to be removed have already been
95 deleted. However, using this option requires fastrm to do more
96 internal work and it also assumes that the order of directory
97 listings is stable in the presence of calls to unlink(2) between
98 calls to readdir(3). This may be a dangerous assumption with some
99 sophisticated file systems (and in general this option is only
100 useful with file systems that use unindexed linear searches to find
101 files in directories or when most of the files to be removed have
102 already been deleted).
103 This optimization is off by default.
105 -u[N]
107 Specifying this option promises that there are no symbolic links in
108 the directory tree from which files are being removed. This allows
109 fastrm to make an additional optimization to its calls to chdir(2),
110 constructing a relative path using "../.." and the like to pass to
111 chdir(2) rather than always using absolute paths. Since this
112 reduces the number of directory lookups needed with deeply nested
113 directory structures (such as that typically created by traditional
114 news spool storage), it can be a significant optimization, but it
115 breaks horribly in the presence of symbolic links to directories.
116 When -u is given, fastrm will use at most N levels of ".."
118 segments to construct paths. N is optional; if just -u is given,
119 -u1 is assumed.
120 This optimization is off by default.
122 fastrm also accepts -a and -r options, which do nothing at all except
124 allow you to say "fastrm -usa", "fastrm -usr", or "fastrm -user".
125 These happen to often be convenient sets of options to use.
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128 fastrm exits with a status of zero if there were no problems, and an
129 exit status of 1 if something went wrong. Attempting to remove a file
130 that does not exist is not considered a problem.
131
133 fastrm is typically invoked by INN via expirerm(8) using a command
134 like:
135 fastrm -e <patharticles in inn.conf> < expire.list
137 To enable all optimizations and see the affect on the order of removal
139 caused by -s, use:
140 fastrm -d -s -e -u <patharticles> < expire.list
142 If your file system has indexed directory lookups, but you have a
144 deeply nested directory structure, you may want to use a set of flags
145 like:
146 fastrm -e -u3 <patharticles> < expire.list
148 to strongly prefer relative paths but not to use readdir(2) to order
150 the calls to unlink(2).
151 You may want to edit expirerm(8) to change the flags passed to fastrm.
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155 fastrm cuts corners and does not worry about security, so it does not
156 use chdir(2) safely and could be tricked into removing files other than
157 those that were intended if run on a specially constructed file tree or
158 a file tree that is being modified while it is running. It should
159 therefore never be used with world-writable directories or any other
160 directory that might be controlled or modified by an attacker.
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163 fastrm defers opening the storage subsystem or attempting to parse any
164 INN configuration files until it encounters a token in the list of
165 files to remove. It's therefore possible to use fastrm outside of INN
166 as a general fast file removal program.
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169 fastrm was originally written by <kre@munnari.oz.au>. This manual page
170 was rewritten in POD by Russ Allbery <eagle@eyrie.org> for
171 InterNetNews.
172 $Id: fastrm.pod 9767 2014-12-07 21:13:43Z iulius $
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176 expirerm(8).
177INN 2.6.4 2015-09-12 FASTRM(1)