ureadahead
Read files in advance during boot
Synopsis
ureadahead
[OPTIONS]... [PACK]
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description
ureadahead
(über-readahead) is used during boot to read files in
advance of when they are needed such that they are already
in the page cache, improving boot performance.
When started
without any arguments, it checks for the existance and age
of the default pack file /var/lib/ureadahead/pack,
and if not present or older than a month, will discard it
and retrace the boot sequence. The pack will then contain
information about the files opened during boot, and the
blocks that were in memory at the completion of the
boot.
If the file
exists and is newer than a month old, or an alternate
PACK path is given on the command-line, the files
listed in the pack are opened and the blocks read into the
page cache using the readahead(2) system call.
Pack files are
automatically optimised for Solid-State Disks or rotational
Hard Drives, depending on which you have.
options
--verbose
May be used to report on
ureadahead’s operation. In particular, this
causes information about the size of the pack file to be
output when reading and a complete dump of the contents of
the pack file after tracing.
--daemon
Places ureadahead into
the background once the pack file has been read, or once
tracing has been enabled.
This is ignored
when reading on rotational hard drives, since it’s
important for performance reasons not to contend with other
processes for I/O.
--force-trace
Discards all pack files and
forces re-tracing.
--timeout=SECONDS
Normally when tracing,
ureadahead will wait for a TERM or INT
signal before concluding and generating the pack file. This
option instead sets a timeout after which tracing is
terminated.
--dump
Dump the contents of the pack file to standard output in
a pretty format, does not trace or read the contents into
memory.
--sort=SORT
Used with --dump to sort
the output.
The default is
open, which is the order that the files will be
opened. path sorts by path name, disk sorts by
on-disk location, and size sorts by the amount of
data that will be read for that file.
copyright
Copyright © 2009 Canonical Ltd.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE.
files
/var/lib/ureadahead/pack
other mount points
PACK need not be the filename of a pack, instead it may be
the name of a mount point (or indeed any non-file within the
filesystem), in which case the pack for that device is read
instead. This allows ureadahead to be called in the style
ureadahead /usr for filesystems split across
multiple devices.
Pack files for these other devices are also stored under
/var/lib/ureadahead and are named
mountpoint.pack
When tracing, these will be automatically generated.
bugs
Report bugs at
<https://launchpad.net/ubuntu/+source/ureadahead/+bugs>
see also
readahead
author
Written by
Scott James Remnant <scott[:at:]netsplit[:dot:]com>