February 2006 - main

Could this happen on Linux?
by Ted.Harding＠nessie.mcc.ac.uk 18 Feb '06

18 Feb '06

Hi Folks, I've just been reading a shocking story on R-devel (the developers' mailing list for the R statistical programming language). Quote: "Over on R-help, the old problem of floating point precision has come up again (see my example below, where calling RSiteSearch can change the results of the var() function). The problem here is that on Windows many DLLs set the precision of the fpu to 53 bit mantissas, whereas R normally uses 64 bit mantissas. (Some Microsoft docs refer to these as 64 bit and 80 bit precision respectively, because they count the sign and exponent bits too). When R calls out to the system, if one of these DLLs gets control, it may change the precision and not change it back. This can happen for example in calls to display a file dialog or anything else where a DLL can set a hook; it's very hard to predict." In other words (if I understand aright), certain programs or processes can change the way the CPU functions when doing floating point arithmetic with the result that other programs will subsequently operate in a different FP environment and get different answers. I'd like to think that Linux was immune to this kind of thing, but can't see an a priori refutation of the possibility. What are the informed views on such a question? Best wishes to all, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <Ted.Harding(a)nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 18-Feb-06 Time: 16:12:56 ------------------------------ XFMail ------------------------------

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Anyone for Fat Cat tonight?
by David Noble 17 Feb '06

17 Feb '06

Anyone for Fat Cat tonight? --Daven

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Belkin PCI wireless card
by Ian bell 17 Feb '06

17 Feb '06

I am having some trouble configuring a newly acquired belkin wireless network card. I have it working but it is a kludge and I don't know why it works so I would like some advice. I have sorted the kernel module (rt2500.o) and I have added modprobe wlan0 to the end of rc.modules tp load it. It loads ok and I can ifconfig to my heart's content but it won't connect to my wireless router. I ran netconfig to set up dhcp but the client dhcpcd does not seem to get run. Running from the console does nothing but await the timeout. route shows just the local loopback. However, by accident I discovered that if I ran kwifi and configured the card to look for my router in infrastructure mode, then if I run dhcpcd wlan0 everything works. route shows that dhcp has made the necessary connections. OK I can do this manually every time but I don't understand what it is that kwifi is doing. Obviously there is a step I am missing somewhere. Can anyone help? I am running Slackare 10.1 Cheers Ian

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Colour lasers
by Barry Samuels 16 Feb '06

16 Feb '06

I want to get a colour laser printer but find the offerings rather confusing. Can anyone recommend one to work with Linux from experience? I want it to be capable of producing good prints from digital photographic images as well as general documents. I know that any Postscript printer should work with Linux but I remember seeing someone on ALUG say don't get one which uses Postscript as a layer over the printer's native language because it makes printing slow. A number of printers describe 'Postscript emulation' or 'Postscript simulation' - is there any difference? Are these the slow ones? Very often it is not clear whether a particular printer is true Postscript or not. What would I have to spend to get a true Postscript printer? Which ones should I avoid? -- Barry Samuels http://www.beenthere-donethat.org.uk The Unofficial Guide to Great Britain

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How to become another user, without password, but keep environment?
by Chris Green 16 Feb '06

16 Feb '06

In my role at work at the moment I frequently have to become other users (mostly build management logins rather than specific user logins). To make this easier for myself I put myself in the user's .rhosts file so that I don't have to give the password every time I become the other user. This is inside a small[ish] development group so this doesn't raise any difficult security issues really. However if you 'rlogin -l newuser hostname' you get newuser's environment. This is OK sometimes but often is a bit of a pain because I need to reset DISPLAY to get X applications to work on my screen and I also lose my favourite editor, etc., etc. So is there any way to preserve the environment in the same way that would happen if I did an 'su newuser' but, on the other hand, allow me to login in without entering the password (as I can with rlogin)? I can thing of various nasty scripting ways of doing it but su is so close to what I want it seems a pity to re-invent an almost invented wheel. -- Chris Green (chris(a)areti.co.uk) "Never ascribe to malice that which can be explained by incompetence."

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Firewall routing problems
by Stuart Bailey 16 Feb '06

16 Feb '06

Hi, I have a customer who is try to give me access to some data for testing, on one of their server, port 5000. If I telnet to their port from my server, I can't get a connection, unless I disable my firewall - not something I like to do. If I look at a tcpdump for port 5000, I can see the connection going out to the internet (5000 is enable in my firewall), and I can see that the masquerading ports are in the same range as when I send SMTP or HTTP packets - which work fine. Any ideas what else can be causing the problem? I'm using Guarddog to configure the iptables. Many thanks. Stuart. -- --------------------------------------- Stuart Bailey BSc (hons) CEng CITP MBCS LinuSoft (Proprietor) Linux Specialist (01953) 601294 (07778) 383739 http://www.linusoft.co.uk ----------------------------------------

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Hosting questions
by Chris Green 15 Feb '06

15 Feb '06

My wife wants to register a set of domains for a small (long term) project she's thinking of starting. I've checked and a nice set of 'same name' domains are available as .com, .co.uk and .biz. The question is should I just register the domains and host them on the home Linux system or can I get a reasonable deal from anywhere for hosting and registration all in one go? Can anyone recommend a single registration company/site which can do all these TLDs at a reasonable price? I've used Just The Names for my isbd.ltd.uk domain and they are reasonably priced for .com and .co.uk but they're expensive for .biz. If I host them on the home system (which already hosts isbd.ltd.uk forwarded from Just The Names) is it possible to 'virtual host' a number of domains even when they're registered with (possibly) different companies? -- Chris Green (chris(a)areti.co.uk) "Never ascribe to malice that which can be explained by incompetence."

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[OT] Fault puzzle
by Ted.Harding＠nessie.mcc.ac.uk 14 Feb '06

14 Feb '06

Hi Folks, Your experience may help here. Today I was phoned by a friend who'd switched on her PC only to get the message "Operating system not found", together with the observation that "DHCP" and "MBA" had come up on screen. The only special circumstance was that the machine had been left unused and switched off for just over a week. So I went round and had a look. Switch on, and enter Setup. Check Boot Order: Floppy, CD-ROM, HDD, Network, and MBA-UNDI. So decided that this was consistent with failing to boot off HDD and proceeding to try booting off the network ("DHCP") which failed (since no network) and then "MBA-UNDI" (whatever that is). So tabbed over to IDE setup to see what whas there, or not. Apparently the HDD and its parameters showed up OK. So quit Setup without saving and let it re-boot. Success: clean boot off HDD. Repeatable -- shut down, switch off, disconnect from mains, re-connect, switch on -> clean re-boot as if nothing had ever happened. Provisionally, therefore, thought that the week's off-time had resulted in the CMOS battery draining, so that it had lost its data which were somehow restored when I went into Setup and poked around. But then it occurred to me that if that were so, then the CMOS clock should have the wrong time (e.g. some hours or days slow). Not so: in fact it was 5 minutes fast. So that seems to not favour my hyptohesis. Leaving me wondering what might really have happened. The only thing I did was have a look inside the Setup and re-boot, not altering a thing. Any ideas? With thanks, and best wishes to all, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <Ted.Harding(a)nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 13-Feb-06 Time: 22:00:00 ------------------------------ XFMail ------------------------------

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Netmasks and IP addresses for dual homed hosts
by Peter Onion 14 Feb '06

14 Feb '06

All of my boxes have got ethernet AND wireless interfaces and everything works fine, but I want to move to using "zeroconf" networking so I don't have to maintain /etc/hosts files on every machine (or go to the bother of setting up a proper DNS server). I've got the avahi daemon working and nss-mdns is working for resolving ".local" host names. Now seems like a good time to review the way I've allocated IP addresses to hosts. My ADLS modem/ethernet router/WiFi access point is a Dlink DSL-G640T which has the address 192.168.1.1 How would you assign addresses to hosts that have wired and wireless interfaces? BTW at home I normally run with the Wireless interfaces turned off but use them if I take machines "away from home" so I don't have to bother with network cables and hubs etc. However laptops sometimes gets used with wireless interfaces at home. Peter

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How to create an email autoresponder?
by Ian Douglas 13 Feb '06

13 Feb '06

Hi Folks, My little business currently has an automated brochure service describing the products we sell. The company has an "info" email address to which people can send keywords and receive an automatically generated email response describing that particular product. At the moment this "autoresponder" function is carried out by an ancient PC chugging away in a forgotten corner running Microsoft Outlook Express and using this program's message filtering rules to select and return the appropriate email/s in response to the keywords in incoming emails. It seems to work quite well and reliably but I was wondering if there was a Linux email prog which we could run on our fileserver to do this? I looked at this a year or so ago and found that although kmail (for example) could filter messages on keywords in the message body it was unable to respond by using this keyword to select an appropriate email reply (out of a possible 20) and actually send it (although kmail may have improved since then). Do any ALUGers already have a Linux based automated brochure service / email autoresponder running on their server? If so could you pass on some tips on how you set it up? Best wishes, Ian.

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