Read files in advance during boot
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(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.
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
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.
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.
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.
Discards all pack files and
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
Dump the contents of the pack file to standard output in
a pretty format, does not trace or read the contents into
Used with --dump to sort
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 © 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.
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
Pack files for these other devices are also stored under
/var/lib/ureadahead and are named
When tracing, these will be automatically generated.
Report bugs at
Scott James Remnant <scott[:at:]netsplit[:dot:]com>