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SYSTEMD-READAHEAD-REPLAsystemd-readahead-reSYSTEMD-READAHEAD-REPLAY.SERVICE(8)

NAME
       systemd-readahead-replay.service, systemd-readahead-collect.service,
       systemd-readahead-done.service, systemd-readahead-done.timer, systemd-
       readahead - Disk read ahead logic
SYNOPSIS
       systemd-readahead-replay.service
       systemd-readahead-collect.service
       systemd-readahead-done.service
       systemd-readahead-done.timer
       /usr/lib/systemd/systemd-readahead/systemd-readahead [OPTIONS...]
                                                            COMMAND
                                                            [DIRECTORY | FILE]
DESCRIPTION
       systemd-readahead-collect.service is a service that collects disk usage
       patterns at boot time.  systemd-readahead-replay.service is a service
       that replays this access data collected at the subsequent boot. Since
       disks tend to be magnitudes slower than RAM, this is intended to
       improve boot speeds by pre-loading early at boot all data on disk that
       is known to be read for the complete boot process.
       systemd-readahead-done.service is executed a short while after boot
       completed and signals systemd-readahead-collect.service to end data
       collection. On this signal, this service will then sort the collected
       disk accesses and store information about them in /.readahead.
       Normally, both systemd-readahead-collect.service and
       systemd-readahead-replay.service are activated at boot so that access
       patterns from the preceding boot are replayed and new data collected
       for the subsequent boot. However, on read-only media where the
       collected data cannot be stored, it might be a good idea to disable
       systemd-readahead-collect.service.
       On rotating media, when replaying disk accesses at early boot,
       systemd-readahead-replay.service will order read requests by their
       location on disk. On non-rotating media, they will be ordered by their
       original access timestamp. If the file system supports it,
       systemd-readahead-collect.service will also defragment and rearrange
       files on disk to optimize subsequent boot times.
OPTIONS
       systemd-readahead understands the following options:
       --files-max=
           Maximum number of files to read ahead. Only valid for thes collect
           command.
       --file-size-max=
           Maximum size of files in bytes to read ahead. Only valid for the
           collect and replay commands.
       --timeout=
           Maximum time in microseconds to spend collecting data. Only valid
           for the collect command.
       -h, --help
           Print a short help text and exit.
       --version
           Print a short version string and exit.
COMMANDS
       The following commands are understood by systemd-readahead:
       collect [DIRECTORY]
           Collect read-ahead data on early boot. When terminating, it will
           write out a pack file to the indicated directory containing the
           read-ahead data.
       replay [DIRECTORY]
           Perform read-ahead on the specified directory tree.
       analyze [FILE]
           Dumps the content of the read-ahead pack file to the terminal. For
           each file, the output lists approximately how much will be read
           ahead by the replay command.
SEE ALSO
       systemd(1)

systemd 219                                SYSTEMD-READAHEAD-REPLAY.SERVICE(8)