The fsck and bcachefs scripts simply worked by running 'exec bcachefs
...', but this executes whatever is out of `$PATH`, which is likely not
what a user expected when working inside the bcachefs-tools tree.
This replaces the local uses of 'exec bcachefs' to use bash's
readlink/dirname builtins in order to find the location of the currently
executing wrapper, and execute the 'bcachefs' tool from there.
This allows executing these wrappers from anywhere, provided 'bcachefs'
is just right next to them, with the correct semantics.
As a result, this also allows removing a tiny hack from the Nix
expressions, allowing the included default.nix to use completely
standard mkDerivation builders, with no extra patch/fixup phases.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
This adds Nix expressions for bcachefs-tools that are modular, work in
purely sandboxed build environments (e.g. on NixOS itself, or macOS, where
sandboxing is enabled by default), use a fixed copy of Nixpkgs (to avoid hidden,
global state) and uses standard build idioms.
This change uses a fixed version of Nixpkgs, one that will always be used for
every build of bcachefs-tools, for all users, rather than relying on whatever
copy of Nixpkgs the user has available.
This has a major benefit in that it allows the build to work in sandboxed
environments such as NixOS, and it correctly declares all of the necessary
dependencies that bcachefs-tools needs. This is done simply by using
stdenv.mkDerivation in order to write a "normal" Nix expression, where the
previous version used a variant of the stdenv builder, but this isn't needed for
the most part. (Doing this has other knock-on benefits, such as the usage of
standardized options like `enableParallelBuild = true;` -- allowing `nix-build`
to automatically do parallel builds, etc.)
Another major benefit of this change is that anyone can now use `nix-shell` to
develop/hack on bcachefs-tools incrementally; simply running nix-shell will put
you in a Bash shell environment where all of bcachefs-tools' dependencies are
proprerly provided, no matter the state of the outside build environment/host
operating system:
$ nix-shell
[nix-shell:~/src/bcachefs-tools]$ make -j4 # works immediately
As mentioned before, with this change, by default, nix-build and
nix-shell run using a prepackaged copy of an upstream Nixpkgs snapshot. This is
done purely to ensure anyone who builds bcachefs-tools using Nix does, in fact,
get a reproducible build. Without this, nix-build defaults to using the the
`<nixpkgs>` NIX_PATH entry in order to fetch dependencies; meaning that two
users on different channels will get different results (for example, if you have
the November 2017 channel but I have the October 2017 channel, the results may
be different).
With this patch, a user running
$ nix-build
will always use the exact same copy of nixpkgs to bootstrap the build,
regardless of whatever channels the user has. This bootstrap mechanism does not
even depend on an existing copy of Nixpkgs itself; e.g. it can work with a
completely empty `NIX_PATH`.
This is arguably anti-modular, but for end-user applications like
bcachefs-tools, fixing the version of Nixpkgs is not normally a huge deal. Users
who wish to use a different copy of Nixpkgs can provide this with an argument to
nix-build directly, using the `nixpkgs` argument to the expression:
$ nix-build --pure --arg nixpkgs 'import <nixpkgs> {}'
This uses the `<nixpkgs>` provided inside your `NIX_PATH` environment variable
to acquire dependencies, which by default is managed using `nix-channel`. If you
have a copy of the Nixpkgs source code e.g. from a `git clone`, you may use that
too by simply using `-I` to prepend your Nixpkgs to `NIX_PATH` (see `man
nix-build` for more):
$ nix-build --pure \
-I nixpkgs=$HOME/src/nixpkgs \
--arg nixpkgs 'import <nixpkgs> {}'
Signed-off-by: Austin Seipp <aseipp@pobox.com>
This removes the implicit `-I libbcachefs` argument to $(CC), which in turn
requires a set of minor changes throughout the tools. There are two advantages
to this setup:
1) It is (arguably) easier to read, since the location of bcachefs includes
are easier to understand at a glance ("where does util.h live?")
2) It removes the need for a hack to include glibc's copy of
dirent.h explicitly via '/usr/include/dirent.h', because libbcachefs/
*also* has a dirent.h file and the compiler cannot disambiguate them.
This has some ramifications on systems where /usr/include may not
exist, such as NixOS.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
We will not always have .git available in some cases. For example, if someone
simply downloaded a tarball of the tree, or if we're building with something
like Nix and want to exclude the .git folder, we need to cope and build the
source anyway.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
