Cisco Nexus Application Development - SDK

This chapter contains the following topics:

About the Cisco SDK

The Cisco SDK is a development kit that contains all the tools to build applications for execution on a Cisco Nexus switch running the Cisco NX-OS Release 9.2(2t). The basic components are the C cross-compiler, linker, libraries, and header files that are commonly used in many applications. The list is not exhaustive, and you might need to download and build any dependencies that are needed for any particular application. Some applications are ready to be downloaded and used from the Cisco devhub website and do not require building. The SDK can be used to build RPM packages which may be directly installed on a switch.

Installing the SDK

The following lists the system requirements:

  • The SDK can run on most modern 64-bit x86_64 Linux systems. It has been verified on CentOS 7 and Ubuntu 14.04. Install and run the SDK under the Bash shell.

  • The SDK includes binaries for both 32-bit and 64-bit architectures, so it must be run on an x86_64 Linux system that also has 32-bit libraries installed.

Procedure

Check if the 32-bit libraries are installed:

Example:

bash$ ls /lib/ld-linux.so.2

If this file exists, then 32-bit libraries should be installed already. Otherwise, install 32-bit libraries as follows:

  • For CentOS 7: 

    bash$ sudo yum install glibc.i686

  • For Ubuntu 14.04: 

    bash$ sudo apt-get install gcc-multilib

Procedure for Installation and Environment Initialization

The SDK is available for download at: https://devhub.cisco.com/artifactory/open-nxos/.

This file is a self-extracting archive that installs the SDK into a directory of your choice. You are prompted for a path to an SDK installation directory. 

bash$ ./wrlinux-8.0.0.25-glibc-x86_64-n9000-nxos-image-rpm-sdk-sdk.sh
Wind River Linux SDK installer version 8.0-n9000
================================================
Enter target directory for SDK (default: /opt/windriver/wrlinux/8.0-n9000): 
You are about to install the SDK to "/opt/windriver/wrlinux/8.0-n9000". Proceed[Y/n]? Y
Extracting SDK...............................................................................done
Setting it up...done
SDK has been successfully set up and is ready to be used.

Each time that you want to use the SDK in a new shell session, you will need to source the environment setup script. For example:

$ . /opt/windriver/wrlinux/8.0-n9000/environment-setup-x86-wrsmllib32-linux
$ . /opt/windriver/wrlinux/8.0-n9000/environment-setup-x86_64-wrs-linux
bash$

Use the source environment-setup-x86-wrsmllib32-linux and source environment-setup-x86_64-wrs-linux commands to add the SDK-specific paths to your shell environment. Add the SDK-specific paths for each shell you intend to use with the SDK. Adding the SDK-specific paths is the key to setting up the SDK to use the correct versions of the build tools and libraries.

Procedure

Step 1

Browse to the installation directory.

Step 2

Enter the following commands at the Bash prompt: 

bash$ source environment-setup-x86-wrsmllib32-linux
bash$ source environment-setup-x86_64-wrs-linux

Using the SDK to Build Applications

Many of the common Linux build processes work for this scenario. Use the techniques that are best suited for your situation.

The source code for an application package can be retrieved in various ways. For example, you can get the source code either in tar file form or by downloading from a git repository where the package resides.

The following are examples of some of the most common cases.

(Optional) Verify that the application package builds using standard configure/make/make install. 

bash$ tar --xvzf example-app.tgz
bash$ mkdir example-lib-install
bash$ cd example-app/
bash$ ./configure --prefix=/path/to/example-app-install
bash$ make
bash$ make install

Sometimes it is necessary to pass extra options to the ./configure script, for example to specify which optional components and dependencies are needed. Passing extra options depends entirely on the application being built.

Example - Build Ganglia and its dependencies

In this example, we build ganglia, along with the third-party libraries that it requires - libexpat, libapr, and libconfuse.

libexpat 

bash$ wget 'http://downloads.sourceforge.net/project/expat/expat/2.1.0/expat-2.1.0.tar.gz'
bash$ mkdir expat-install
bash$ tar xvzf expat-2.1.0.tar.gz
bash$ cd expat-2.1.0
bash$ ./configure --prefix=/home/sdk-user/expat-install
bash$ make
bash$ make install
bash$ cd ..

libapr 

bash$ wget 'http://www.eu.apache.org/dist/apr/apr-1.5.2.tar.gz'
bash$ mkdir apr-install
bash$ tar xvzf apr-1.5.2.tar.gz
bash$ cd apr-1.5.2
bash$ ./configure --prefix=/home/sdk-user/apr-install
bash$ make
bash$ make install
bash$ cd ..

libconfuse


Note

confuse requires the extra --enable-shared option to ./configure, otherwise it builds a statically linked library instead of the required shared library. 

bash$ wget 'http://savannah.nongnu.org/download/confuse/confuse-2.7.tar.gz'
bash$ mkdir confuse-install
bash$ tar xvzf confuse-2.7.tar.gz
bash$ cd confuse-2.7
bash$ ./configure --prefix=/home/sdk-user/confuse-install --enable-shared
bash$ make
bash$ make install
bash$ cd ..

ganglia


Note

The locations to all the required libraries are passed to ./configure. 

bash$ wget 'http://downloads.sourceforge.net/project/ganglia/ganglia%20monitoring%20core/3.7.2/ganglia-3.7.2.tar.gz'
bash$ mkdir ganglia-install
bash$ tar xvzf ganglia-3.7.2.tar.gz
bash$ cd ganglia-3.7.2
bash$ ./configure --with-libexpat=/home/sdk-user/expat-install --with-libapr=/home/sdk-user/apr-install/bin/apr-1-config --with-libconfuse=/home/sdk-user/confuse-install --prefix=/home/sdk-user/ganglia-install
bash$ make
bash$ make install
bash$ cd ..

Using RPM to Package an Application

If the application successfully builds using "make", then it can be packaged into an RPM.


Note
RPM and spec files

The RPM package format is designed to package up all files (binaries, libraries, configurations, documents, etc) that are needed for a complete install of the given application. The process of creating an RPM file is therefore somewhat non-trivial. To aid in the RPM build process, a .spec file is used that controls everything about the build process.


Note

Many third-party applications are available on the internet in the form of source code packaged into tarballs. In many cases, these tarballs will include a .spec file to help with RPM build process. Unfortunately, many of these .spec files are not updated as frequently as the source code itself. Even worse, sometimes there is no spec file at all. In these cases the spec file may need editing or even creating from scratch so that RPMs can be built.

Creating an RPM Build Environment

Before using the SDK to build RPMs, an RPM build directory structure must be created, and some RPM macros set.

Procedure

Step 1

Create the directory structure: 

bash$ mkdir rpmbuild
bash$ cd rpmbuild
bash$ mkdir BUILD RPMS SOURCES SPECS SRPMS
Step 2

Set the topdir macro to point to the directory structure created above: 

bash$ echo "_topdir ${PWD}" > ~/.rpmmacros
Note 

This step assumes that the current user does not already have a .rpmmacros file that is already set up. If it is inconvenient to alter an existing .rpmmacros file, then the following may be added to all rpmbuild command lines: 

--define "_topdir ${PWD}"
Step 3

Refresh the RPM DB: 

bash$ rm /path/to/sdk/sysroots/x86_64-wrlinuxsdk-linux/var/lib/rpm/__db.*
bash$ rpm --rebuilddb
Note 

The rpm and rpmbuild tools in the SDK have been modified to use /path/to/sdk/sysroots/x86_64-wrlinuxsdk-linux/var/lib/rpm as the RPM database instead of the normal /var/lib/rpm. This modification prevents any conflicts with the RPM database for the host when not using the SDK and removes the need for root access. After SDK installation, the SDK RPM database must be rebuilt through this procedure.

Using General RPM Build Procedure

General RPM Build procedure is as follows: 

bash$ wget --no-check-certificate --directory-prefix=SOURCES http://<URL of example-app tarball>
bash$ # determine location of spec file in tarball:
bash$ tar tf SOURCES/example-app.tar.bz2 | grep '.spec$'
bash$ tar xkvf SOURCES/example-app.tar.bz2 example-app/example-app.spec
bash$ mv example-app/example-app.spec SPECS/
bash$ rm -rf example-app
bash$ rpmbuild -v --bb SPECS/example-app.spec

The result is a binary RPM in RPMS/ that can be copied to the switch and installed. Installation and configuration of applications can vary. Refer to the application documents for those instructions.

This rpmbuild and installation on the switch is required for every software package that is required to support the application. If a software dependency is required that is not already included in the SDK, the source code must be obtained and the dependencies built. On the build machine, the package can be built manually for verification of dependencies. The following example is the most common procedure: 

bash$ tar xkzf example-lib.tgz
bash$ mkdir example-lib-install
bash$ cd example-lib/
bash$ ./configure --prefix=/path/to/example-lib-install
bash$ make
bash$ make install

These commands place the build files (binaries, headers, libraries, and so on) into the installation directory. From here, you can use standard compiler and linker flags to pick up the location to these new dependencies. Any runtime code, such as libraries, are required to be installed on the switch also, so packaging required runtime code into an RPM is required.


Note

There are many support libraries already in RPM form on the Cisco devhub website.

Example to Build RPM for collectd with No Optional Plug-Ins

Download source tarball and extract spec file: 

bash$ wget --no-check-certificate --directory-prefix=SOURCES https://collectd.org/files/collectd-5.5.0.tar.bz2
bash$ tar tf SOURCES/collectd-5.5.0.tar.bz2 | grep '.spec$'
collectd-5.5.0/contrib/redhat/collectd.spec
collectd-5.5.0/contrib/aix/collectd.spec
collectd-5.5.0/contrib/sles10.1/collectd.spec
collectd-5.5.0/contrib/fedora/collectd.spec
bash$ tar xkvf SOURCES/collectd-5.5.0.tar.bz2 collectd-5.5.0/contrib/redhat/collectd.spec
bash$ mv collectd-5.5.0/contrib/redhat/collectd.spec SPECS/
bash$ rm -rf collectd-5.5.0

There are four spec files in this tarball. The Red Hat spec file is the most comprehensive and is the only one that contains the correct collectd version. We will use it as an example.

This spec file sets the RPM up to use /sbin/chkconfig to install collectd. However on a switch, you will use the /usr/sbin/chkconfig instead. Edit the following edited in the spec file: 

bash$ sed -r -i.bak 's%(^|\s)/sbin/chkconfig%\1/usr/sbin/chkconfig%' SPECS/collectd.spec

collectd has numerous optional plug-ins. This spec file enables many plug-ins by default. Many plug-ins have external dependencies, so options to disable these plug-ins must be passed to the rpmbuild command line. Instead of typing out one long command line, we can manage the options in a Bash array as follows: 

bash$ rpmbuild_opts=()
bash$ for rmdep in \
> amqp apache ascent bind curl curl_xml dbi ipmi java memcachec mysql nginx \
> notify_desktop notify_email nut openldap perl pinba ping postgresql python \
> rrdtool sensors snmp varnish virt write_http write_riemann
> do
>  rpmbuild_opts+=("--without")
>  rpmbuild_opts+=(${rmdep})
> done
bash$ rpmbuild_opts+=(--nodeps)
bash$ rpmbuild_opts+=(--define)
bash$ rpmbuild_opts+=("_unpackaged_files_terminate_build 0")

It is then passed to rpmbuild as follows to start the entire build and RPM package process: 

bash$ rpmbuild "${rpmbuild_opts[@]}" -bb SPECS/collectd.spec

You can then find the resulting RPMs for collectd in the RPMS directory.

These RPM files can now be copied to the switch and installed from the switch Bash shell: 

bash$ rpm --noparentdirs -i /bootflash/collectd-5.5.0-1.ia32e.rpm

Example to Build RPM for collectd with Optional Curl Plug-In

The collectd curl plug-in has libcurl as a dependency.

In order to satisfy this link dependency during the RPM build process, it is necessary to download and build curl under the SDK: 

bash$ wget --no-check-certificate http://curl.haxx.se/download/curl-7.24.0.tar.gz
bash$ tar xkvf curl-7.24.0.tar.gz
bash$ cd curl-7.24.0
bash$ ./configure --without-ssl --prefix /path/to/curl-install
bash$ make
bash$ make install
bash$ cd ..

Note
The curl binaries and libraries are installed to /path/to/curl-install. This directory will be created if it does not already exist, so you must have write permissions for the current user. Next, download the source tarball and extract the spec file. This step is exactly the same as in the collectd example for no plugins. 
bash$ wget --no-check-certificate --directory-prefix=SOURCES https://collectd.org/files/collectd-5.5.0.tar.bz2
bash$ tar tf SOURCES/collectd-5.5.0.tar.bz2 | grep '.spec$'
collectd-5.5.0/contrib/redhat/collectd.spec
collectd-5.5.0/contrib/aix/collectd.spec
collectd-5.5.0/contrib/sles10.1/collectd.spec
collectd-5.5.0/contrib/fedora/collectd.spec
bash$ tar xkvf SOURCES/collectd-5.5.0.tar.bz2 collectd-5.5.0/contrib/redhat/collectd.spec
bash$ mv collectd-5.5.0/contrib/redhat/collectd.spec SPECS/
bash$ rm -rf collectd-5.5.0

Note
There are four spec files in this tarball. The Red Hat spec file is the most comprehensive, and it is the only one to contain the correct collectd version. We will use that one as an example.

This spec file sets the RPM up to use /sbin/chkconfig to install collectd. However on a switch, you must use /usr/sbin/chkconfig instead, so the following can be edited in the spec file: 

bash$ sed -r -i.bak 's%(^|\s)/sbin/chkconfig%\1/usr/sbin/chkconfig%' SPECS/collectd.spec

Here a deviation from the previous example is encountered. The collectd rpmbuild process needs to know the location of libcurl. Edit the collectd spec file to add the following.

Find the string %configure in SPECS/collectd.spec. This line and those following it define the options that rpmbuild will pass to the ./configure script.

Add the following option: 

--with-libcurl=/path/to/curl-install/bin/curl-config \

Next a Bash array is built again to contain the rpmbuild command options. Note the following differences:

  • curl is removed from the list of plug-ins not to be built

  • The addition of --with curl=force 

bash$ rpmbuild_opts=()
bash$ for rmdep in \
> amqp apache ascent bind curl_xml dbi ipmi java memcachec mysql nginx \
> notify_desktop notify_email nut openldap perl pinba ping postgresql python \
> rrdtool sensors snmp varnish virt write_http write_riemann
> do
>  rpmbuild_opts+=("--without")
>  rpmbuild_opts+=(${rmdep})
> done
bash$ rpmbuild_opts+=("--with")
bash$ rpmbuild_opts+=("curl=force")bash$ rpmbuild_opts+=(--nodeps)
bash$ rpmbuild_opts+=(--define)
bash$ rpmbuild_opts+=("_unpackaged_files_terminate_build 0")

It is then passed to rpmbuild as follows to start the entire build and RPM package process: 

bash$ rpmbuild "${rpmbuild_opts[@]}" -bb SPECS/collectd.spec

The resulting RPMs in the RPMs directory will now also include collectd-curl. These RPM files can now be copied to the switch and installed from the switch Bash shell: 

bash$ rpm --noparentdirs -i /bootflash/collectd-5.5.0-1.ia32e.rpm
bash$ rpm --noparentdirs -i /bootflash/collectd-curl-5.5.0-1.ia32e.rpm