lfs_cleanerd(8) - NetBSD Manual Pages

LFS_CLEANERD(8)         NetBSD System Manager's Manual         LFS_CLEANERD(8)


NAME

     lfs_cleanerd -- garbage collect a log-structured file system


SYNOPSIS

     lfs_cleanerd [-bcDdfmqs] [-i segment-number] [-l load-threshhold]
                  [-n number-of-segments] [-r report-frequency] [-t timeout]
                  node


DESCRIPTION

     The lfs_cleanerd command starts a daemon process which garbage-collects
     the log-structured file system residing at the point named by node in the
     global file system namespace.  This command is normally executed by
     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.

     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.

     The following options are available:

     -b      Use bytes written, rather than segments read, when determining
             how many segments to clean at once.

     -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.

     -D      Stay in the foreground, do not become a daemon process.  Does not
             print additional debugging information (in contrast to -d).

     -d      Run in debug mode.  Do not become a daemon process, and print
             debugging information.  More -d s give more detailed debugging
             information.

     -f      Use filesystem idle time as the criterion for aggressive clean-
             ing, instead of system load.

     -i segment-number
             Invalidate the segment with segment number segment-number.  This
             option is used by resize_lfs(8), and should not be specified on
             the command line.

     -l load-threshhold
             Clean more aggressively when the system load is below the given
             threshhold.  The default threshhold is 0.2.

     -m      Does nothing.  This option is present for historical compatibil-
             ity.

     -n 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 -b
             was also given, pass this many segments' worth of blocks through
             a single call to lfs_markv.

     -q      Quit after cleaning once.

     -r report-frequency
             Give an efficiency report after every report-frequency times
             through the main loop.

     -s      When cleaning the file system, send only a few blocks through
             lfs_markv at a time.  Don't use this option.

     -t timeout
             Poll the filesystem every timeout seconds, looking for opportuni-
             ties to clean.  The default is 300, that is, five minutes.  Note
             that lfs_cleanerd will be automatically awakened when the
             filesystem is active, so it is not usually necessary to set
             timeout to a low value.


SEE ALSO

     lfs_bmapv(2), lfs_markv(2), lfs_segwait(2), mount_lfs(8)


HISTORY

     The lfs_cleanerd utility first appeared in 4.4BSD.

NetBSD 8.0                      August 6, 2009                      NetBSD 8.0