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FASTRM(1)		  InterNetNews Documentation		     FASTRM(1)

NAME
       fastrm -	Quickly	remove a list of files

SYNOPSIS
       fastrm [-de] [-c|-cI] [-s|-sM] [-u|-uN] base-directory

DESCRIPTION
       fastrm reads a list of either file names	or storage API tokens, one per
       line, from its standard input and removes them.	Storage	API tokens are
       removed via the SMcancel() interface.  fastrm does not delete files
       safely or with an eye to	security, but rather cuts every	corner it can
       to delete files as fast as it can.  It should therefore never be	run on
       publically writable directories,	or in any other	environment where a
       hostile party may control the directory structure in which it is
       working.

       If a file name is not an	absolute path name, it is considered to	be
       relative	to base-directory as given on the command line.	 The base-
       directory parameter must	be a simple absolute pathname (it must not
       contain multiple	consecutive slashes or references to the special
       directories "." or "..").

       fastrm is designed to be	faster than the	typical	"| xargs rm" pipeline
       when given a sorted list	of file	names as input.	 For example, fastrm
       will usually chdir(2) into a directory before removing files from it,
       meaning that if its input is sorted, most names passed to unlink(2)
       will be simple names.  This can substantially reduce the	operating
       system overhead from directory lookups.

       fastrm assumes that its input is	valid and that it is safe to call
       unlink(2) on every file name it is given.  As a safety measure,
       however,	fastrm when running as root will check with stat(2) that a
       file name doesn't specify a directory before removing it.  (In some
       operating systems, root is allowed to unlink directories, even
       directories which aren't	empty, which can cause file system
       corruption.)

       The input to fastrm should always be sorted -- or even better be	in the
       order file names	are output by find(1) -- if speed is an	issue and the
       input isn't solely storage API tokens.  (It deals fine with unsorted
       input, but is unlikely to be any	faster in that case than a simple "|
       xargs rm" command.)  Sorting may	even slightly speed up the removal of
       storage API tokens due to caching effects, since	sorting	will tend to
       keep all	of the tokens from a particular	storage	method together.

       Various additional optimizations	for removing files can be turned on
       and/or tuned with options (see below).  Which options will be most
       effective depends heavily on the	underlying structure of	the file
       system, the way in which	directories are	stored and searched, and
       similar,	often underdocumented, operating system	implementation
       details.	 The more sophisticated	the underlying operating system	and
       file system, the	more likely that it will already perform the
       equivalent of these optimizations internally.

OPTIONS
       -c[I]
	   Controls when fastrm	calls chdir(2).	 If the	number of files	to be
	   unlinked from a given directory is at least I, then fastrm will
	   change to that directory before unlinking those files.  Otherwise,
	   it will use either the absolute path	names or a path	name relative
	   to the current directory (whichever is likely more efficient).  The
	   I parameter is optional; if just -c is given, -c1 is	assumed, which
	   will	cause fastrm to	always chdir before calling unlink(2).	The
	   default is -c3.  Use	-c0 to prevent fastrm from ever	using
	   chdir(2).

       -d  Don't remove	any files.  Instead, print a list of the files that
	   would be removed to standard	output.	 Each line contains either the
	   current directory of	fastrm at the time it would do the unlink and
	   the relative	path name it would pass	to unlink(2) as	two fields
	   separated by	whitespace and a "/", the absolute path	name (as a
	   single field) that would be passed to unlink(2), or the string
	   "Token" and the storage API token that would	be removed.

       -e  Treat an empty input	file as	an error.  This	is most	useful when
	   fastrm is last in a pipeline	after a	preceding sort(1) command,
	   ensuring that fastrm	will fail if the sort fails.

       -s[M]
	   When	-s is given and	the number of files to remove in a directory
	   is greater than M, rather than remove files in the order given,
	   fastrm will open the	directory and read it, unlinking files in the
	   order that they appear in the directory.  On	systems	with a per-
	   process directory cache or that use a linear	search to find files
	   in a	directory, this	should make directory lookups faster.  The M
	   parameter is	optional; if just -s is	given, -s5 is assumed.

	   When	this option is in effect, fastrm won't attempt to remove files
	   that	it doesn't see in the directory, possibly significantly
	   speeding it up if most of the files to be removed have already been
	   deleted.  However, using this option	requires fastrm	to do more
	   internal work and it	also assumes that the order of directory
	   listings is stable in the presence of calls to unlink(2) between
	   calls to readdir(3).	 This may be a dangerous assumption with some
	   sophisticated file systems (and in general this option is only
	   useful with file systems that use unindexed linear searches to find
	   files in directories	or when	most of	the files to be	removed	have
	   already been	deleted).

	   This	optimization is	off by default.

       -u[N]
	   Specifying this option promises that	there are no symbolic links in
	   the directory tree from which files are being removed.  This	allows
	   fastrm to make an additional	optimization to	its calls to chdir(2),
	   constructing	a relative path	using "../.." and the like to pass to
	   chdir(2) rather than	always using absolute paths.  Since this
	   reduces the number of directory lookups needed with deeply nested
	   directory structures	(such as that typically	created	by traditional
	   news	spool storage),	it can be a significant	optimization, but it
	   breaks horribly in the presence of symbolic links to	directories.

	   When	-u is given, fastrm will use at	most N levels of ".."
	   segments to construct paths.	 N is optional;	if just	-u is given,
	   -u1 is assumed.

	   This	optimization is	off by default.

       fastrm also accepts -a and -r options, which do nothing at all except
       allow you to say	"fastrm	-usa", "fastrm -usr", or "fastrm -user".
       These happen to often be	convenient sets	of options to use.

EXIT STATUS
       fastrm exits with a status of zero if there were	no problems, and an
       exit status of 1	if something went wrong.  Attempting to	remove a file
       that does not exist is not considered a problem.

EXAMPLES
       fastrm is typically invoked by INN via expirerm(8) using	a command
       like:

	   fastrm -e <patharticles in inn.conf>	< expire.list

       To enable all optimizations and see the affect on the order of removal
       caused by -s, use:

	   fastrm -d -s	-e -u <patharticles> < expire.list

       If your file system has indexed directory lookups, but you have a
       deeply nested directory structure, you may want to use a	set of flags
       like:

	   fastrm -e -u3 <patharticles>	< expire.list

       to strongly prefer relative paths but not to use	readdir(2) to order
       the calls to unlink(2).

       You may want to edit expirerm(8)	to change the flags passed to fastrm.

WARNINGS
       fastrm cuts corners and does not	worry about security, so it does not
       use chdir(2) safely and could be	tricked	into removing files other than
       those that were intended	if run on a specially constructed file tree or
       a file tree that	is being modified while	it is running.	It should
       therefore never be used with world-writable directories or any other
       directory that might be controlled or modified by an attacker.

NOTES
       fastrm defers opening the storage subsystem or attempting to parse any
       INN configuration files until it	encounters a token in the list of
       files to	remove.	 It's therefore	possible to use	fastrm outside of INN
       as a general fast file removal program.

HISTORY
       fastrm was originally written by	<kre@munnari.oz.au>.  This manual page
       was rewritten in	POD by Russ Allbery <eagle@eyrie.org> for
       InterNetNews.

       $Id: fastrm.pod 9767 2014-12-07 21:13:43Z iulius	$

SEE ALSO
       expirerm(8).

INN 2.6.1			  2015-09-12			     FASTRM(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | EXAMPLES | WARNINGS | NOTES | HISTORY | SEE ALSO

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