John Ashmead on 20 Mar 2012 08:06:06 -0700

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Re: [PLUG] PLUG W follow-up

And second that thanks to Bruce!  very interesting presentation!  good coverage both of replication & of Postgres's role in that.  

It was particularly interesting to see the comparison of Slony's use of triggers and of Postgres 9's use of the Write-Ahead-Log.  I've worked with both approaches & like triggers when only a bit of the database needs to be replicated (there was a business case for keeping the history) but suspect use of the WAL is a more general, lower overhead solution.

I'd like to thank JP & the group for the info on distros:  I'm an old unix hand but my experience with Linux is casual:  I'm setting up a few Linuxes now.

Discussion post meeting was a blast!  Really wide range of topics, time travel, clovis culture, epigenetics, frogs or was it toads, ...  

And thanks to JP for digging up his Stonehenge time travel reference (I do time travel talks at SF conventions so am always looking for more raw material!).  And for his references:  I've just ordered the "Why Software Sucks".  

On epigenetics I would recommend "Evolution in Four Dimensions" which I found a real eye opener:  as we discussed last night, there is a lot more to evolution then just the genes & the phenotypes.



On Mar 20, 2012, at 4:14 AM, JP Vossen wrote:

Thanks to Bruce for his interesting talk on PostgreSQL Replication. (Boy, MySQL is a heck of a lot easier to spell and type! :)

Before the preso we talked about what Linux Distro to use.  That's obviously too open-ended to answer, but some of the suggestions were:

RPM (Used to mean Red Hat Package Manager, now recursing for RPM) based:

APT (Advanced Package Tool) based:


Some noted that Fedora and Ubuntu are not suitable for a production server because they change too fast and are end-of-lifed too fast.  In my opinion that is true for Fedora, but Ubuntu does have a server product and the periodic LTS (Long Term Support) releases targets at slower moving Enterprise customers.  Having said that...

*Personally* I prefer Debian on the server and Ubuntu LTS on the desktop, though in my recent (last 2 years or so) experience both have declined in stability.  I prefer Debian's old "ship when it's ready" to the newer "ship every X period".  I agree the latter makes it easier to plan, but I think the former was more solid and stable.  When I have to use RPM-based, I use CentOS, and we do use a lot of CentOS, RHEL and even (shudder) OEL at $WORK.

A lot of it comes down to what you are used to, and how closely the distro's philosophy meshes with how your mind works.  I find Debian just works the way I think.  Ubuntu used to, being based on Debian, but I don't like Gnome3 (upstream, not Canonical's fault) and I have mixed feelings on Unity.  Since I'd also argue that servers should not have GUI's, that all may be moot, at least for now.

Any of the above, plus many other Linux distros, will work fine in the majority of cases.  Given specific details or constraints, some will work better than others at this or that.  It all depends on the details...

After the preso Amul & I were talking about enabling VNC on Ubuntu 10.10.  Using the GUI this would be System > Preferences > Remote Desktop, but he doesn't have the GUI, that's the point behind needing VNC in the first place.

So from the command line via SSH:

# As the user who owns the GUI desktop
# This will show you the current settings
$ gconftool-2 -a /desktop/gnome/remote_access

# This will show only the ones we care about:
$ gconftool-2 --get /desktop/gnome/remote_access/enabled
$ gconftool-2 --get /desktop/gnome/remote_access/view_only
$ gconftool-2 --get /desktop/gnome/remote_access/prompt_enabled

# This will set them so that:
# [x] Allow other users to view your desktop
# [x] Allow other users to control your desktop
# [ ] You must confirm each access to this machine
$ gconftool-2 --set --type=bool /desktop/gnome/remote_access/enabled true
$ gconftool-2 --set --type=bool /desktop/gnome/remote_access/view_only false
$ gconftool-2 --set --type=bool /desktop/gnome/remote_access/prompt_enabled false

HOWEVER...  I just tried the stuff above and it didn't seem to work. I'd get a useless "Connection Closed" message immediately on trying to connect.  So I went upstairs to check the machine and it seemed correct.  A 'netstat -lnp' only showed this, which looked odd since it seems IPv6 only while I'm using IPv4:
tcp6  0  0 :::5900    :::*  LISTEN      30673/vino-server

I didn't change anything, but when I went back to my office and tried again it sort-of worked, in that I could connect, but once it painted once the screen wouldn't refresh.  Then I remembered that VNC and Compiz don't play nice, at least in the Ubuntu 10.04 LTS that I'm using. System > Preferences > Appearance > Visual Effects = None "fixes" that.  (Remote desktop using Ubuntu 10.04+ with Compiz & Unity ought to be...interesting...)

So maybe:
$ gconftool-2 -s --type bool /apps/metacity/general/compositing_manager false
# Or probably better:
$ gconftool-2 --set /desktop/gnome/remote_access/disable_xdamage --type bool true


At dinner we discussed a great number of interesting things, much of which had nothing to do with Linux or F/OSS.  Here are a couple of references that came up.

SciFi author Harry Harrison has done a few time travel pieces, but his short story "The Secret of Stonehenge" is the one I was talking about. It's in either of these two anthologies: _Stainless Steel Visions_ or _Prime Number_.

Author also came up, and I would add and maybe for related reading (I'm a big fan of Norman, though for software you also want David S Platt (  And of course Asimov's excellent and classic short story "The Last Question" (

I think the Nova "frog thing" I was trying to remember was the epigenetics "Ghost in Your Genes" documentatary, more info here:

Wow, as usual this got way too long...  Hope it's useful,
JP Vossen, CISSP            |:::======|
My Account, My Opinions     |=========|
"Microsoft Tax" = the additional hardware & yearly fees for the add-on
software required to protect Windows from its own poorly designed and
implemented self, while the overhead incidentally flattens Moore's Law.
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