nerfed

Purpose

Some archiving applications (tar) lacks options for not performing privileged operations (e.g. mknod), and to enforce archive permissions (chmod) when unpacking an archive. In the case where you are looking to automating unpacking and would like to avoid enforcing some calls due to looking at OS archives, or if you want to automate extracting content of broken archives (containing e.g. folders with the wrong mode), you can just nerf these libc functions: Make them happily return success without action.

The features and inner workings are similar to fakeroot, but where fakeroot takes care to serve a consistent view of anything written to the file system, nerfed will just throw this information away.

Variants

nerfed comes in three flavors:

• nerfed-embedded: Embeds the library within the executable and writes it to /tmp before using it for LD_PRELOAD.
• nerfed-separate: Expects to find the library on a static location in the file system, typically /usr/libexec/nerfed/libeat-function.so. This path can be changed using the PREFIX or PRELOAD_SO_PATH arguments to make.
• libeat-function.so: Library used by the above commands, but with a stable interface that can be used without the helper executables.

Usage

To use with e.g. tar and ignore mknod and chmod:

nerfed --chmod --mknod tar -zxf archive.tar.gz

To accomplish the same action using the library directly:

env LD_PRELOAD=/path/to/libeat-function.so LIBEAT_FUNCTION_CHMOD=1 LIBEAT_FUNCTION_MKNOD=1 tar -zxf archive.tar.gz