How to fix cargo error: The system library `libudev` required by crate `libudev-sys` was not found.

Problem

During cargo build or cargo run, you see an error message such as

example.txt
 error: failed to run custom build command for `libudev-sys v0.1.4`

Caused by:
  process didn't exit successfully: `/home/uli/dev/MyProject/target/debug/build/libudev-sys-83d6f195a2f9191c/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-env-changed=LIBUDEV_NO_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_x86_64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_x86_64_unknown_linux_gnu
  cargo:rerun-if-env-changed=HOST_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG
  cargo:rerun-if-env-changed=LIBUDEV_STATIC
  cargo:rerun-if-env-changed=LIBUDEV_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_STATIC
  cargo:rerun-if-env-changed=PKG_CONFIG_ALL_DYNAMIC
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH_x86_64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH_x86_64_unknown_linux_gnu
  cargo:rerun-if-env-changed=HOST_PKG_CONFIG_PATH
  cargo:rerun-if-env-changed=PKG_CONFIG_PATH
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR_x86_64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR_x86_64_unknown_linux_gnu
  cargo:rerun-if-env-changed=HOST_PKG_CONFIG_LIBDIR
  cargo:rerun-if-env-changed=PKG_CONFIG_LIBDIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_x86_64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_x86_64_unknown_linux_gnu
  cargo:rerun-if-env-changed=HOST_PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR

  --- stderr

  thread 'main' (952655) panicked at /home/uli/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/libudev-sys-0.1.4/build.rs:38:41:
  called `Result::unwrap()` on an `Err` value: "\npkg-config exited with status code 1\n> PKG_CONFIG_ALLOW_SYSTEM_LIBS=1 PKG_CONFIG_ALLOW_SYSTEM_CFLAGS=1 pkg-config --libs --cflags libudev\n\nThe system library `libudev` required by crate `libudev-sys` was not found.\nThe file `libudev.pc` needs to be installed and the PKG_CONFIG_PATH environment variable must contain its parent directory.\nThe PKG_CONFIG_PATH environment variable is not set.\n\nHINT: if you have installed the library, try setting PKG_CONFIG_PATH to the directory containing `libudev.pc`.\n"
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...

Solution

Your Rust project depends on the libudev-sys crate, which, in turn, depends on the system udev library.

On Ubuntu, install it using

example.sh
sudo apt -y install libudev-dev

After that, you can retry your cargo command.


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