.TH eatmydata 1 "November 2014"
.SH NAME
eatmydata \- transparently disable fsync() and other data-to-disk synchronization calls
.SH SYNOPSIS
.B eatmydata
[--] \fIcommand\fR [ \fIcommand arguments\fR ... ]
.SH DESCRIPTION
\fBeatmydata\fR runs a command in the environment where data-to-disk
synchronization calls (like fsync(), fdatasync(), sync(), msync() and open()
O_SYNC / O_DSYNC flags) have no effect. LD_PRELOAD library \fBlibeatmydata\fR
overrides respective C library calls with custom functions that don't trigger
synchronization but return success nevertheless.
.P
You may use \fBeatmydata\fR in two ways. In normal mode, just execute
\fBeatmydata\fR directly and pass a command\-to\-be\-run and its arguments via
command line. In order to use symlink mode, create a symlink to
\fI/usr/bin/eatmydata\fR with the filename (a.k.a basename) of another program
in the PATH and execute \fBeatmydata\fR via that symlink. Then \fBeatmydata\fR
will find that program in the PATH and run it in the libeatmydata environment
repassing all command line options.
.SH OPTIONS
.P
Please note that \fBeatmydata\fR does not process any command line options in
symlink mode. All command line options will be repassed to the underlying
executable as-is.
.TP
.I command
The command to execute. It may be either a full path or the name of the command
in PATH. In case command cannot be found in PATH, \fBeatmydata\fR will fail.
.TP
.I command arguments
Arbitrary number of arguments to pass to the command being executed.
.TP
--
Optional command separator for compatibility with similar utilities. Ignored at
the moment.
.SH EXAMPLES
.P
Given PATH is /usr/bin and both /usr/bin/aptitude and /usr/bin/eatmydata are
installed, the following:
.P
.nf
    $ ln \-s /usr/bin/eatmydata ./aptitude
    $ ./aptitude moo
.fi
.P
is equivalent to:
.P
.nf
    $ eatmydata \-\- aptitude moo
.fi
.P
Therefore, you may use symlink mode to automatically run specific programs in
the libeatmydata environment whenever you run them from PATH. For example,
given standard PATH settings, just do:
.P
.nf
    # ln \-s /usr/bin/eatmydata /usr/local/bin/aptitude
.fi
.P
and enjoy sync\-free aptitude system-wide.
.SH CAVEAT
.P
When using \fBeatmydata\fR with \fBsetarch\fR (including alias such as
\fBlinux32\fR), or anyway with chroots with a different architectures than the
host's, make sure to install the matching architecture of
\fBlibeatmydata1\fR both in the \fBsetarch\fR environment and host's.
.P
Trying to load libeatmydata manually (without using the wrapper script) and
using it through a chroot, especially if the eatmydata version differ between
outside and inside, is probably going to fail do the different position of the
library on the file system.
.br
The safest way to manually load libeatmydata is by setting the following two
environment variables (shell syntax):
.P
.nf
    LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+"$LD_LIBRARY_PATH:"}/usr/lib/libeatmydata
    LD_PRELOAD=${LD_PRELOAD:+"$LD_PRELOAD "}libeatmydata.so
.fi
.P
These two variables accounts the case of a Debian Jessie host with a Debian
Wheezy chroot, where the position of the library changed.