Introduction to Rust

The Rust programming language is designed to be a safe, concurrent, practical language.

This package is updated on a six-weekly release cycle. Because it is such a large and slow package to build, is at the moment only required by a few packages in this book, and particularly because newer versions tend to break older mozilla packages, the BLFS editors take the view that it should only be updated when that is necessary (either to fix problems, or to allow a new version of a package to build).

As with many other programming languages, rustc (the rust compiler) needs a binary from which to bootstrap. It will download a stage0 binary at the start of the build, so you cannot compile it without an Internet connection.



Although BLFS usually installs in /usr, when you later upgrade to a newer version of rust the old libraries in /usr/lib/rustlib will remain, with various hashes in their names, but will not be usable and will waste space. The editors recommend placing the files in the /opt directory. In particular, if you have reason to rebuild with a modified configuration (e.g. using the shipped LLVM after building with shared LLVM, perhaps to compile crates for architectures which the BLFS LLVM build does not support) it is possible for the install to leave a broken cargo program. In such a situation, either remove the existing installation first, or use a different prefix such as /opt/rustc-1.76.0-build2.

If you prefer, you can of course change the prefix to /usr.

The current rustbuild build-system will use all processors, although it does not scale well and often falls back to just using one core while waiting for a library to compile. However it can be mostly limited to a specified number of processors by a combination of adding the switch --jobs <N> (e.g. '--jobs 4' to limit to 4 processors) on each invocation of python3 and using an environment variable CARGO_BUILD_JOBS=<N>. At the moment this is not effective when some of the rustc tests are run.

The current version of rust's num_cpus crate now recognizes that cgroups can be used to restrict which processors it is allowed to use. So if your machine lacks DRAM (typically, less than 2GB DRAM per core) that might be an alternative to taking CPUs offline. Read the section called “Use Linux Control Group to Limit the Resource Usage” for how to use a cgroup.

At the moment Rust does not provide any guarantees of a stable ABI.



Rustc defaults to building for ALL supported architectures, using a shipped copy of LLVM. In BLFS the build is only for the X86 architecture. If you intend to develop rust crates, this build may not be good enough for your purposes.

The build times of this version when repeated on the same machine are often reasonably consistent, but as with all compilations using rustc there can be some very slow outliers.

This package is known to build and work properly using an LFS 12.1 platform.

Package Information

  • Download (HTTP):

  • Download MD5 sum: 14a8ac688b461a3127090cad513aee05

  • Download size: 155 MB

  • Estimated disk space required: 8.9 GB (298 MB installed); add 6.4 GB if running the tests

  • Estimated build time: 6.7 SBU (including download time; add 6.2 SBU for tests, both using parallelism=8)

Additional Downloads

Rust Dependencies


CMake-3.28.3 and cURL-8.6.0



An Internet connection is needed for building this package.




If a recommended dependency is not installed, a shipped copy in the Rustc source tarball will be built and used.


GDB-14.1 (used by the test suite if it is present), git-2.44.0 (required by the test suite), cranelift, jemalloc, libgccjit (read command explanation in GCC-13.2.0), and libgit2

Editor Notes:

Installation of Rust



Currently the rust compiler produces SSE2 instructions for 32-bit x86, causing the generated code to be broken on 32-bit systems without a SSE2-capable processor. All x86 processor models released after 2004 should be SSE2-capable. Run lscpu | grep sse2 as a test. If it outputs anything, your CPU is SSE2-capable and OK. Otherwise you may try to build this package on a SSE2-capable system with the following fix applied:

sed 's@pentium4@pentiumpro@' -i \

And copy the resulting /opt/rustc-1.76.0 to the system without SSE2 capability. But this change is still under upstream review and not tested by BLFS editors.

To install into the /opt directory, remove any existing /opt/rustc symlink and create a new directory (i.e. with a different name if trying a modified build of the same version). As the root user:

mkdir -pv /opt/rustc-1.76.0      &&
ln -svfn rustc-1.76.0 /opt/rustc


If multiple versions of Rust are installed in /opt, changing to another version only requires changing the /opt/rustc symbolic link and then running ldconfig.

If running the test suite, apply a patch to prevent the build system from unnecessarily rebuilding the compiler:

patch -Np1 -i ../rustc-1.76.0-testsuite_fix-1.patch

Create a suitable config.toml file which will configure the build.

cat << EOF > config.toml
# see config.toml.example for more possible options
# See the 8.4 book for an old example using shipped LLVM
# e.g. if not installing clang, or using a version before 13.0

# Tell the editors have reviewed the content of this file
# and updated it to follow the major changes of the building system,
# so will not warn us to do such a review.
change-id = 118703

# by default, rust will build for a myriad of architectures
targets = "X86"

# When using system llvm prefer shared libraries
link-shared = true

# omit docs to save time and space (default is to build them)
docs = false

# install extended tools: cargo, clippy, etc
extended = true

# Do not query new versions of dependencies online.
locked-deps = true

# Specify which extended tools (those from the default install).
tools = ["cargo", "clippy", "rustdoc", "rustfmt"]

# Use the source code shipped in the tarball for the dependencies.
# The combination of this and the "locked-deps" entry avoids downloading
# many crates from Internet, and makes the Rustc build more stable.
vendor = true

prefix = "/opt/rustc-1.76.0"
docdir = "share/doc/rustc-1.76.0"

channel = "stable"
description = "for BLFS 12.1"

# BLFS used to not install the FileCheck executable from llvm,
# so disabled codegen tests.  The assembly tests rely on FileCheck
# and cannot easily be disabled, so those will anyway fail if
# FileCheck has not been installed.
#codegen-tests = false

# Enable the same optimizations as the official upstream build.
lto = "thin"
codegen-units = 1

# NB the output of llvm-config (i.e. help options) may be
# dumped to the screen when config.toml is parsed.
llvm-config = "/usr/bin/llvm-config"

# NB the output of llvm-config (i.e. help options) may be
# dumped to the screen when config.toml is parsed.
llvm-config = "/usr/bin/llvm-config"


The python3 commands may output a warning message complaining no codegen-backends config matched the requested path to build a codegen backend. And the provided suggestion (add backend to codegen-backends in config.toml) will not silence it. This warning is bogus and it should be ignored.

Compile Rust by running the following commands:

{ [ ! -e /usr/include/libssh2.h ] ||
  export LIBSSH2_SYS_USE_PKG_CONFIG=1; } &&
python3 build


The test suite will generate some messages in the systemd journal for traps on invalid opcodes, and for segmentation faults. In themselves these are nothing to worry about, just a way for the test to be terminated.

To run the tests (again using all available CPUs) issue:

SSL_CERT_DIR=/etc/ssl/certs \
python3 test --verbose --no-fail-fast | tee rustc-testlog

Two tests,tests/ui/issues/ and tests/debuginfo/, are known to fail.

If FileCheck from LLVM has not been installed, all 47 tests from the assembly suite will fail.

As with all large test suites, other tests might fail on some machines - if the number of additional failures is low, check the log for 'failures:' and review lines above that, particularly the 'stderr:' lines. Any mention of SIGSEGV or signal 11 in a failing test is a cause for concern.

If you get any other failing test which reports an issue number then you should search for that issue. For example, when rustc >= 1.41.1 was built with a version of sysllvm before 10.0 the test for issue 69225 failed and that should be regarded as a critical failure (they released 1.41.1 because of it). Most other failures will not be critical.

Therefore, you should determine the number of failures.

The number of tests which passed and failed can be found by running:

grep '^test result:' rustc-testlog |
 awk '{sum1 += $4; sum2 += $6} END { print sum1 " passed; " sum2 " failed" }'

The other available fields are $8 for those which were ignored (i.e. skipped), $10 for 'measured' and $12 for 'filtered out' but both those last two are probably zero.

Now, as the root user, install the package:



If sudo or su is invoked for switching to the root user, ensure LIBSSH2_SYS_USE_PKG_CONFIG is correctly passed or the following command may completely rebuild this package. For sudo, use the --preserve-env=LIBSSH2_SYS_USE_PKG_CONFIG option. For su, do not use the - or --login options.

python3 install

The building system attempts to install some files twice, and during the second attempt it renames the old one (installed in the first attempt) with the .old suffix. As the root user, remove these files:

find /opt/rustc-1.76.0 -name "*.old" -delete

Still as the root user, symlink a Zsh completion file into the correct location:

install -vdm755 /usr/share/zsh/site-functions      &&
ln -sfv /opt/rustc/share/zsh/site-functions/_cargo \

Finally, unset the LIBSSH2_SYS_USE_PKG_CONFIG variable:


Command Explanations

ln -svfn rustc-1.76.0 /opt/rustc: if this is not the first use of the /opt/rustc symlink, overwrite it by forcing, and use the '-n' flag to avoid getting confusing results from e.g. ls -l.

targets = "X86": this avoids building all the available linux cross-compilers (AArch64, MIPS, PowerPC, SystemZ, etc). Unfortunately, rust insists on installing source files for these below /opt/rustc/lib/src.

extended = true: this installs several tools (specified by the tools entry) alongside rustc.

tools = ["cargo", "clippy", "rustdoc", "rustfmt"]: only build the tools from the 'default' profile in binary command rustup which are recommended for most users. The other tools are unlikely to be useful unless using (old) code analyzers or editing the standard library.

channel = "stable": this ensures only stable features can be used, the default in config.toml is to use development features, which is not appropriate for a released version.

[target.x86_64-unknown-linux-gnu]: the syntax of config.toml requires an llvm-config entry for each target for which system-llvm is to be used. Change the target to [target.i686-unknown-linux-gnu] if you are building on 32-bit x86. This whole section may be omitted if you wish to build against the shipped llvm, or do not have clang, but the resulting build will be larger and take longer.

export LIBSSH2_SYS_USE_PKG_CONFIG=1: Allow cargo to link to system libssh2.

SSL_CERT_DIR=/etc/ssl/certs: Work around an issue causing test failures with the CA certificate store layout used by make-ca-1.13.

--verbose: this switch can sometimes provide more information about a test which fails.

--no-fail-fast: this switch ensures that the test suite will not stop at the first error.

Configuring Rust

Configuration Information

If you installed rustc in /opt, you need to update the following configuration files so that rustc is correctly found by other packages and system processes.

As the root user, create the /etc/profile.d/ file:

cat > /etc/profile.d/ << "EOF"
# Begin /etc/profile.d/

pathprepend /opt/rustc/bin           PATH

# Include /opt/rustc/man in the MANPATH variable to access manual pages
pathappend  /opt/rustc/share/man     MANPATH

# End /etc/profile.d/

Immediately after installation, update the current PATH for your current shell as a normal user:

source /etc/profile.d/


Installed Programs: cargo-clippy, cargo-fmt, cargo, clippy-driver, rust-gdb, rust-gdbgui, rust-lldb, rustc, rustdoc, and rustfmt
Installed Libraries: librustc-driver-<16-byte-hash>.so, libstd-<16-byte-hash>.so, and libtest-<16-byte-hash>.so
Installed Directories: ~/.cargo, /opt/rustc, symbolic link to /opt/rustc-1.76.0

Short Descriptions


provides lint checks for a cargo package


formats all bin and lib files of the current crate using rustfmt


is the Package Manager for Rust


provides lint checks for Rust


is a wrapper script for gdb, pulling in Python pretty-printing modules installed in /opt/rustc-1.76.0/lib/rustlib/etc


is a wrapper script for a graphical front end to gdb that runs in a browser


is a wrapper script for LLDB (the LLVM debugger) pulling in the Python pretty-printing modules


is the rust compiler


generates documentation from rust source code


formats rust code


is the Rust Standard Library, the foundation of portable Rust software