eatmydata - Online in the Cloud

PROGRAM:

NAME

eatmydata - transparently disable fsync() and other data-to-disk synchronization calls

SYNOPSIS

eatmydata [--] command [ command arguments ... ]

DESCRIPTION

eatmydata 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 libeatmydata overrides respective C library calls with custom functions
that don't trigger synchronization but return success nevertheless.

You may use eatmydata in two ways. In normal mode, just execute eatmydata directly and
pass a command-to-be-run and its arguments via command line. In order to use symlink mode,
create a symlink to /usr/bin/eatmydata with the filename (a.k.a basename) of another
program in the PATH and execute eatmydata via that symlink. Then eatmydata will find that
program in the PATH and run it in the libeatmydata environment repassing all command line
options.

OPTIONS

Please note that eatmydata does not process any command line options in symlink mode. All
command line options will be repassed to the underlying executable as-is.

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, eatmydata will fail.

command arguments
Arbitrary number of arguments to pass to the command being executed.

-- Optional command separator for compatibility with similar utilities. Ignored at the
moment.

EXAMPLES

Given PATH is /usr/bin and both /usr/bin/aptitude and /usr/bin/eatmydata are installed,
the following:

$ ln -s /usr/bin/eatmydata ./aptitude
$ ./aptitude moo

is equivalent to:

$ eatmydata -- aptitude moo

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:

# ln -s /usr/bin/eatmydata /usr/local/bin/aptitude

and enjoy sync-free aptitude system-wide.

CAVEAT

When using eatmydata with setarch (including alias such as linux32), or anyway with
chroots with a different architectures than the host's, make sure to install the matching
architecture of libeatmydata1 both in the setarch environment and host's.

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.
The safest way to manually load libeatmydata is by setting the following two environment
variables (shell syntax):

LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+"$LD_LIBRARY_PATH:"}/usr/lib/libeatmydata
LD_PRELOAD=${LD_PRELOAD:+"$LD_PRELOAD "}libeatmydata.so

These two variables accounts the case of a Debian Jessie host with a Debian Wheezy chroot,
where the position of the library changed.

November 2014 eatmydata(1)

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