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from: @(#)lfs_cleanerd.8 8.2 (Berkeley) 12/11/93
.Dd August 6, 2009 .Dt LFS_CLEANERD 8 .Os .Sh NAME .Nm lfs_cleanerd .Nd garbage collect a log-structured file system .Sh SYNOPSIS .Nm .Op Fl bcDdfmqs .Op Fl i Ar segment-number .Op Fl l Ar load-threshhold .Op Fl n Ar number-of-segments .Op Fl r Ar report-frequency .Op Fl t Ar timeout
a node .Sh DESCRIPTION The .Nm command starts a daemon process which garbage-collects the log-structured file system residing at the point named by .Ar node in the global file system namespace. This command is normally executed by .Xr mount_lfs 8 when the log-structured file system is mounted. The daemon will exit within a few minutes of when the file system it was cleaning is unmounted.
p Garbage collection on a log-structured file system is done by scanning the file system's segments for active, i.e. referenced, data and copying it to new segments. When all of the active data in a given segment has been copied to a new segment that segment can be marked as empty, thus reclaiming the space taken by the inactive data which was in it.
p The following options are available: l -tag -width indent t Fl b Use bytes written, rather than segments read, when determining how many segments to clean at once. t Fl c Coalescing mode. For each live inode, check to see if it has too many blocks that are not contiguous, and if it does, rewrite it. After a single pass through the filesystem the cleaner will exit. This option has been reported to corrupt file data; do not use it. t Fl D Stay in the foreground, do not become a daemon process. Does not print additional debugging information (in contrast to .Fl d ) . t Fl d Run in debug mode. Do not become a daemon process, and print debugging information. More .Fl d s give more detailed debugging information. t Fl f Use filesystem idle time as the criterion for aggressive cleaning, instead of system load. t Fl i Ar segment-number Invalidate the segment with segment number .Ar segment-number . This option is used by .Xr resize_lfs 8 , and should not be specified on the command line. t Fl l Ar load-threshhold Clean more aggressively when the system load is below the given threshhold. The default threshhold is 0.2. t Fl m Does nothing. This option is present for historical compatibility. t Fl n Ar number-of-segments Clean this number of segments at a time: that is, pass this many segments' blocks through a single call to lfs_markv, or, if .Fl b was also given, pass this many segments' worth of blocks through a single call to lfs_markv. t Fl q Quit after cleaning once. t Fl r Ar report-frequency Give an efficiency report after every .Ar report-frequency times through the main loop. t Fl s When cleaning the file system, send only a few blocks through lfs_markv at a time. Don't use this option. t Fl t Ar timeout Poll the filesystem every .Ar timeout seconds, looking for opportunities to clean. The default is 300, that is, five minutes. Note that .Nm will be automatically awakened when the filesystem is active, so it is not usually necessary to set .Ar timeout to a low value. .El .Sh SEE ALSO .Xr lfs_bmapv 2 , .Xr lfs_markv 2 , .Xr lfs_segwait 2 , .Xr mount_lfs 8 .Sh HISTORY The .Nm utility first appeared in x 4.4 .