Archive for April, 2009

Samba CIFS permission problems

Tuesday, April 21st, 2009

Samba, the implementation of Windows [Personal Computer or PC] type file sharing on Unix type machines, is a classic example of ‘east meets west’ in security models. Unix was always designed as multi-user and it has a clear separation between users and the computer. In the PC world, the culture started out as assuming the user owned the machine and everything connected to it.

For Unix based machines, connecting to a network simply extended its security model to a ‘network is the computer’ idea. In the PC world, it was a case of needing to address a new concern – that of distinguishing self from other. Logins came to the PC and, with that, a whole raft of options and ideas about how to control who could do what.

If security isn’t an issue, permission to do things to files and devices on the network isn’t much of a problem. Just leave the doors open. In Unix systems this means keeping the ‘everyone’ permissions wide open for each file or device. In the PC world, it means setting up shares without conditions. Even then problems can occur when trying to cross the divide.

For instance, it is a common problem when using rsync to backup a Linux file system to a CIFS (PC) share. That share is usually mounted on the Linux system at a point owned by the root user. It may be set wide open but that isn’t the whole story. If you try to run rsync as a non-root user, you might encounter errors that say you do no have permission to set certain attributes. To get around these errors, you have to either run rsync as root or to mount the CIFS share to a mount point you, rather than root, own.

Another common issue in blending Unix and PC security models is that of adding Unix ideas to the PC shares. These often have to to with the user and group identification method used in Unix systems. These ‘Unix extensions’ can mean that the PC share pays attention to Unix user and group ID numbers used to control file permissions in Unix systems. If the Unix clients trying to access the PC shares do not have carefully planned user and group ID numbers used consistently throughout the network, users can have problems when a mismatch causes permission problems. This is why the CIFS filesystem in Linux has options such as nounix, noperms, and so on.

Another method to turn off these Unix extensions to PC share features is to command “sudo echo 0 > /proc/fs/cifs/LinuxExtensionsEnabled” which changes a CIFS parameter. You may need to “sudo modprobe cifs” in order to start the module and get the proc variables established.

There is a lot more to this story …

Posted in Networks, Systems | No Comments »

USB iso boot, Unetbootin or Ubuntu

Tuesday, April 21st, 2009

One of the first things to do these days with a new distribution ISO is to use it to create a bootable USB memory stick. There are three tools at hand for this. One is a simple script, one is Unetbootin, and the third is the (now) default Ubuntu utility.

The Ubuntu utility encountered a problem when the persistent storage was activated. This is a means to be able to create a live boot device you can use to remember your email message store, settings, and bookmarks. It isn’t needed if you only seek to create a bootable USB device to install systems.

Unetbootin works well and its customized boot routines probably offer some advantages. It is also cross platform and set up to customize bootable devices from common Linux distributions and Windows installation CD’s. It didn’t have any problem with the Remastersys created ISO.

The default Ubuntu utility also didn’t have any problem with the Remastersys created ISO. It makes a convenient means to create a USB device to facilitate new version installs.

Posted in Systems, Tools | No Comments »

Remastersys, Jaunty beta, and system printer config

Tuesday, April 21st, 2009

A download and install of the Ubuntu Jaunty beta went without a glitch. All of the extras were installed to get a stable system with all the usual applications running. Remastersys installed successfully, too, and it was used to create a live distribution DVD of the resulting mess.

The Remastersys distribution booted properly and went through the installation as expected. It was only when I went to install printers that I encountered a glitch. I could not add a printer. The system printer configuration problem was a regression to a bug reported several months ago and fixed – something to do with the Python script that provides the GUI for GNOME configuration of CUPS printers. Why Remastersys resurrected this bug would be something to find out.

I’ll wait until both Jaunty and Remastersys have had a chance to settle down and see if this particular problem gets fixed. My guess is that it has something to do with what Remastersys has to assume about the system that changed in the Jaunty update. In the meantime, it means installing the Ubuntu upgrade from the distribution CD and then adding all of the customizations. That isn’t too much of a hassle as the ‘aptitude install’ list is almost an upgrade script and the initialization and configuration needs are minor.

Posted in Systems, Tools | No Comments »

People powered space heat

Thursday, April 16th, 2009

Rules of Thumb cites John Brink, building superintendent, Masonic Temple with “Ten people will raise the temperature of a medium-size room one degree per hour.”

If you calculate the typical 2,000 food Calorie per day diet to an energy flow (power), you get 100 watts. So another way to look at Brink’s rule of thumb is that a kilowatt of heating will warm a medium sized room by a degree per hour.A kilowatt of heating is about what your typical electric space heater provides.

So next time you plan a party with friends in the living room, keep in mind the heat budget!

Posted in Education and Support | No Comments »

Energy costs

Monday, April 13th, 2009

The big black rack box with its PIII was replaced by a Netgear ReadyNAS DUO. That step increased storage by a factor of 7 and reduced noise significantly. It also reduced the power need from 49 watts to 21. With 8760 hours in a year that’s a drop from 429 KwH to 184. The electric rates sheet at NV Energy, Statement of Rates, indicates an electric energy cost of about fifteen cents per kilowatt hour. That means the annual expense drops from about $65 to $28.

The NAS has automatic power down capabilities so it can be turned off for 6 hours or so each night. That reduces the annual hours on to 6570 and the annual power cost to about $21. That’s about $7 per year for the processor and $7 for each hard drive in the NAS.

From a capital cost perspective, the $40+ potential annual energy cost savings would pay for the NAS in something under ten years. Rated life is probably closer to 5 so benefits other than power draw are needed to rationalize its expense.

Posted in Hardware, Systems | No Comments »

Looks like it’s time to buy the White Album, again

Tuesday, April 7th, 2009

The news headlines say Digitally remastered Beatles coming in September. This effort took four years and paid a lot of attention to preserving the original sound with few exceptions. Those exceptions were such things as obviously unintended artifacts such as electrical clicks, and mic pops and hisses (excess sibilance).

Prior to this effort, the Beatles digital media was created from rather straighforward ripping of published sources – the media masters were about as far upstream as the effort went. This effort gets back to the original mixing tapes and equipment then applies modern processing techniques that replicate some of the tricks applied to the original recordings that was unique to the equipment and media of the time.

Of course, this is also major media hype. There will be special packages and provenance add-ons and other stuff to try to sell more. Whatever. It will be interesting to just what 4 years of effort using modern tools will do to create a recording to sound just like it should have forty years ago.

Posted in Multimedia | No Comments »