Not packaged for Precise

As you can see on the packages.ubuntu.com site with a query, this isn't available in Precise (12.04), but only for Quantal (12.10) and newer.

Rather than installing from source, here's how to build your own package from the sources of Quantal.

Manual package build (backport)

This is a very very verbose description - for anyone building a package for the first time.

1. Install basic packages to build software and packages: build-essential and devscripts .




2. Go to the source package (gflags) page at Launchpad: https://launchpad.net/ubuntu/+source/gflags




3. Unfold the section for "The Quantal Quetzal (supported) 2.0-1" version.




4. Locate the source package description file (.dsc extension). At the time of writing this is https://launchpad.net/ubuntu/+archive/primary/+files/gflags_2.0-1.dsc




5. Copy the link to your clipboard.




6. Open a terminal and download the source package using dget:

   
   
   

   dget https://launchpad.net/ubuntu/+archive/primary/+files/gflags_2.0-1.dsc
   
   

   
   
   

   This will fail the first time:

   
   
   

   gpg: Signature made Thu 31 May 2012 14:48:41 CEST using RSA key ID 8AE09345
   
   gpg: Can't check signature: public key not found
   
   Validation FAILED!!
   
   




7. Install the required RSA key as in the error message above:

   
   
   

   gpg --keyserver keyserver.ubuntu.com --recv-key 8AE09345
   
   




8. Configure the DPKG development scripts to use your GPG keyring:

   
   
   

   echo 'DSCVERIFY_KEYRINGS="/etc/apt/trusted.gpg:~/.gnupg/pubring.gpg"' > ~/.devscripts
   
   

   
   
   

   See Added key, but dget still shows "gpg: Can't check signature: public key not found" for why.




9. Run the earlier dget command again. This should now succeed.




10. Hop into the directory created:

    
    
    

    cd gflags-2.0/
    
    




11. Try building the package.

    
    
    

    debuild -uc -us
    
    

    
    
    

    Explanation for the options: unsigned changes file, unsigned new .dsc file. As you are not redistributing the package, there's no need to sign anything.

    
    
    

    This may fail due to missing build dependencies, e.g.:

    
    
    

    dpkg-checkbuilddeps: Unmet build dependencies: debhelper
    
    

    
    
    

    Note this is really system specific.




12. Install the build dependencies (satisfy all above from the output you get), e.g.:

    
    
    

    sudo apt-get install debhelper
    
    




13. Try building the package again:

    
    
    

    debuild -uc -us
    
    




14. One directory below, you'll find your packages, e.g.:

    
    
    

    $ cd ..
    
    $ ls -al *gflags*.deb
    
    -rw-r--r-- 1 gert gert 108450 Jun 24 18:59 libgflags2_2.0-1_amd64.deb
    
    -rw-r--r-- 1 gert gert 147590 Jun 24 18:59 libgflags-dev_2.0-1_amd64.deb
    
    -rw-r--r-- 1 gert gert  14778 Jun 24 18:59 libgflags-doc_2.0-1_all.deb
    
    




15. Install them:

    
    
    

    sudo dpkg -i *gflags*.deb
    
    

    
    
    

    In case this fails because of binary dependencies not satisfied, run

    
    
    

    sudo apt-get install -f
    
    

Done!

You can remove or update them any time, like any other package.

The next time you will build any package you will not have to go through all the hoops... in general the recipe is like:

1. dget <.dsc-file>




2. cd thefolder




3. debuild -uc -us




4. sudo dpkg -i ../*somepattern*.deb