wxPython is Kicking my Ass!

Let me preface by saying that I’m not a programmer nor software developer nor anything of the sorts. I’m a sysadmin with scripting skills to solve automation problems, for the most part. I took all the C++ classes in High School but I never pursued software development as a serious academic interest or career. I know “about” software development and it’s practices but I don’t feel that I have any particularly interesting skills in the field.

Now that I want to write a site-specific GUI-based LDAP management tool as referenced in a previous post, I’m jumping back into software development a little bit. I’ve decided to use wxPython for a few reasons. We already use it within our group, we have in-house expertise in the form of an actual developer and the GUI-builder tools seem to work best with wxPython (wxGlade was producing bad wxPerl code, go figure).

Let me also say that I’ve never been a big python guy. I’m really a perl kind of dude, so this learning a new object oriented API while learning python at the same time is a challenge… but I’m making progress! Basically, wxPython seriously kicked my ass for about 3 days but now I’m gaining speed and things are moving faster than I expected. Python and wxPython are starting to make more sense and behave.

So far I have a frame with menubar, statusbar and a three-tabbed notebook with a grid on each tab of the notebook. The program is able to connect to an LDAP server (with TLS) and query the directory for all the users, groups and autofs information and then display that information in the grid… and that’s about it so far. I need to build in new user, group and autofs functionality as well as basic editing of existing entries (in place editing with wx.Grid looks really nice but I haven’t tried it yet!).

Although my ass has been kicked for the last few days, I’m actually feeling pretty optimistic about it now.

Hopefully I can share the kludge code at some point, though it will never be easily transportable to different environments since I’m not building this to be the end-all-be-all LDAP user/group/autofs management tool, just one tailored for our environment.

Cfengine 3 Snippets Part 1: DenyHosts

I’ve recently begun looking into configuration management with cfengine 3. I’ve ignored this growing sub-field of system administration for too long and I just can’t ignore it anymore. After spending quite some time researching the philosophies, methods and different tools out there, I settled on starting out with cfengine 3. There’s no special reason that I chose cfengine instead of puppet, bcfg2, chef or AutomateIT. I haven’t used any of these tools and thus I cannot pass judgement on them or their methods. All these projects seem to have intelligent and highly motivated people behind them. I simply gravitated towards cfengine because of its strong academic background and the fact that version 3 now represents the most recent and modern research in the field by Mark Burgess et. al.

As part of my learning experience with cfengine, I’ve decided to start posting some of the code that I’ve begun developing in the hopes that by writing about it, I can learn better, faster and maybe even receive some helpful comments from readers along the way. Beware, I’m a cfengine newbie and so what I post here should NOT be copy and pasted into your environment unless you’re ok with the potential of wildly breaking things!

The first snippet of code I want to discuss is related to managing our DenyHosts configuration. As part of our “security policy”, I would like to ensure that every RedHat/CentOS system is running a properly configured DenyHosts instance. Here is what I’ve come up with so far.


RHEL/CentOS, NFS and Firewalls

I recently decided that it’s about time to setup consistent, explicit and tight firewall policy across our Linux (mostly RHEL/CentOS) servers. One of the initial issues I faced was NFS. NFS implementations are very well known to make use of the portmapper and dynamically assigned port for rpc.mountd and because of this dynamic assignment, firewalling NFS can be challenging.

Luckily, RedHat’s /etc/sysconfig/nfs configuration file read by¬† various “nfs”, “nfslock” and RPC services init scripts provides an easy means of locking down specific ports for all the NFS-related services so that one doesn’t have to work around the dynamic port assignment problem when it comes to firewalling.