17 Jun 2016 • on

Habitat Tips & Tricks

In the first 48 hours with habitat, here are a few things that I’ve learned.

1. Debugging hab builds

You can see additional output if you prefix any hab command with DEBUG=1

[0][default:/src:0]# DEBUG=1 build

$ DEBUG=1 hab pkg build . -k yourdepot

2. Extract a habitat file

.hart files are basically just a tarball with metadata. You can explode the contents using tail, xzcat and tar

tail -n +6 /tmp/foo-bar.hart | xzcat | tar xf - -C .

The files will be extracted to the current directory.

3. Use variables from other habitat packages

Suppose you have a jar. How do you set JAVA_HOME when JAVA_HOME is defined in core/jdk8 ?

Put the following inside hooks/run or hooks/init

export JAVA_HOME=$(hab pkg path core/jdk8)

Example hook file

4. Installing a habitat package you just built from studio

Once you have built a package, you presumably want to test it. At the end of the build notice the line Artifact: /src/results/foo-bar-1.0.0....hart

[0][default:/src:0]# build
....
'/hab/cache/artifacts/spuder-ant-1.9.7-20160617211801-x86_64-linux.hart' -> '/src/results/spuder-ant-1.9.7-20160617211801-x86_64-linux.hart'
   ant: hab-plan-build cleanup
   ant:
   ant: Source Cache: /hab/cache/src/ant-1.9.7
   ant: Installed Path: /hab/pkgs/spuder/ant/1.9.7/20160617211801
   ant: Artifact: /src/results/spuder-ant-1.9.7-20160617211801-x86_64-linux.hart
   ant: Build Report: /src/results/last_build.env
   ant: SHA256 Checksum: 7f6de0e8388212396dafd67152392c72b6456f3eb9814da03cd835cacd7634ef
   ant: Blake2b Checksum: 633a61e417debb57c32ea7c998f546b23fcbf94d45ab44e7dc59bd78e7b67d38
   ant:
   ant: I love it when a plan.sh comes together.
   ant:
   ant: Build time: 0m22s

If you built your package from outside of studio, there will be a file that contains this same information

results/last_build.env

To Install the package that was just created

[0][default:/src:0]# hab pkg install foo/bar

If your package has a runtime, (or service to run) you can start it like so

[0][default:/src:0]# hab start foo/bar

If your package doesn’t have a runtime, but does contain an executable, see the next tip.

5. Test run executable from inside habitat studio

You can test that your binary works using hab pkg exec foo/bar bazz

[0][default:/src:0]# hab pkg install /src/results/foo/bar/1.0.0/xxxx.hart
[1][default:/src:0]# hab pkg exec foo/bar bazz

[0][default:/src:0]# hab pkg exec core/curl curl --version
curl 7.47.1 (x86_64-pc-linux-gnu) libcurl/7.47.1 OpenSSL/1.0.2h zlib/1.2.8
Protocols: dict file ftp ftps gopher http https imap imaps pop3 pop3s smb smbs smtp smtps telnet tftp
Features: IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP UnixSockets

[0][default:/src:0]$ hab pkg exec core/which which --version
GNU which v2.21, Copyright (C) 1999 - 2015 Carlo Wood.
GNU which comes with ABSOLUTELY NO WARRANTY;
This program is free software; your freedom to use, change
and distribute this program is protected by the GPL.

6. Making package from local directory

All the current examples from habitat show examples where the source is downloadable from a url. But what if you want to put your plan.sh file inside your project?

Set pkg_source and pkg_shasum to any made up value (can’t be empty) Override the do_download, do_verify and do_unpack to return 0

pkg_origin=foo
pkg_name=bar
pkg_version=1.0.0
pkg_maintainer='Example <example@example.com>'
pkg_license=('Apache 2')
pkg_distname=$pkg_name
pkg_source='.' # This can't be blank, but setting it to a non http URL does nothing
pkg_shasum='0' # This can't be blank. it will be overwritten later
pkg_deps=()
pkg_build_deps=()

do_download() {
  return 0
}

do_verify() {
  return 0
}

do_unpack() {
  return 0
}

do_build() {
  return 0
}

do_install() {
  # Copy everything from present directory to the root of habitat package
  # $PLAN_CONTEXT = the current directory when studio was started
  # $pkg_prefix = /src (which becomes the root directory of the habitat package)
  cp -a $PLAN_CONTEXT/. $pkg_prefix/
}

7. Understand `pkg_dirname`

When you download and extract a .tar.gz or .zip file containing your source code, it may or may not unzip to a sane directory name.

You can tell habitat where to look for the source code by modifying pkg_dirname

E.g. If source code foobar.tgz extracts to foobar-dumbfolder123

pkg_dirname=${pkg_name}-dumbfolder${pkg_version}