eatmydata - Man Page

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

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.

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.

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.

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.