November 2001 - WLUG - wlug.mailman3.com

RE: [Wlug] Forcing scsi probe on the fly...

by Keller, Tim

This worked perfectly! Thanks, Tim! -----Original Message----- From: Theo Van Dinter [mailto:felicity@kluge.net] Sent: Wednesday, November 28, 2001 2:14 PM To: Worcester Linux User's Group Subject: Re: [Wlug] Forcing scsi probe on the fly... On Wed, Nov 28, 2001 at 01:50:01PM -0500, Keller, Tim wrote: > Does anybody know with Redhat 7.1 (using 2.4.2-2) if theirs a way to force > the scsi chain to rescan its bus (without an unload/reload) of the module? > > so far, I haven't found something like HPUX's ioscan. Unless something's changed, Linux doesn't have the capability to do that yet (the last time I checked, there needs to be some extra functionality added to the kernel SCSI code). Whenever I had to add a device live, there's a thing with /proc/scsi/scsi that you can do (this is from the SCSI Programming HOWTO): Dynamically insert and remove SCSI devices If a newer kernel and the /proc file system is running, a non-busy device can be removed and installed 'on the fly'. To remove a SCSI device: echo "scsi remove-single-device a b c d" > /proc/scsi/scsi and similar, to add a SCSI device, do echo "scsi add-single-device a b c d" > /proc/scsi/scsi where a == hostadapter id (first one being 0) b == SCSI channel on hostadapter (first one being 0) c == ID d == LUN (first one being 0) There's also a script which tries to automate this kind of stuff: http://www.garloff.de/kurt/linux/rescan-scsi-bus.sh I've never tried it, but I've seen it mentioned on a few mailing lists that I monitor. -- Randomly Generated Tagline: "Does anyone not understand what the hell is going on?" - Prof. Bagchi _______________________________________________ Wlug mailing list Wlug(a)mail.wlug.org http://mail.wlug.org/mailman/listinfo/wlug

Nov. 29, 2001

Re: [Wlug] linuxconf/7.1?

by Keith Wright

> From: Bill Mills-Curran <subssn594(a)charter.net> > > I put together a RedHat 7.1 machine recently and was surprised to find > that linuxconf was not part of the default installation. It's clearly > improved over older versions of linuxconf, so why isn't it installed? > Anyone know why? If you check the file RELEASE-NOTES in the root of the first CD, you will see o Deprecated Packages -- the following packages are deprecated, and could disappear in a future release: - linuxconf "Deprecated" is a polite way of saying that it sucks big greasy chunks through a tiny straw. You may disagree, in which case you should write a 'man' page for it. I don't like a huge program that runs at boot time to update configuration files without telling me what it is doing and has no documentation except for some happy talk*. If you want it, you can install it, what's the problem with not installing what you don't ask for? * From /usr/share/doc/linuxconf-1.24r2/RPM-README: Congratulations! You are now running the most powerful Linux administrative tool known to mankind! I guess it's so powerful that nobody can write down what it does. -- -- Keith Wright <kwright(a)free-comp-shop.com> Programmer in Chief, Free Computer Shop <http://www.free-comp-shop.com> --- Food, Shelter, Source code. ---

Nov. 29, 2001

Re: [Wlug] Forcing scsi probe on the fly...

by Theo Van Dinter

On Wed, Nov 28, 2001 at 01:50:01PM -0500, Keller, Tim wrote: > Does anybody know with Redhat 7.1 (using 2.4.2-2) if theirs a way to force > the scsi chain to rescan its bus (without an unload/reload) of the module? > > so far, I haven't found something like HPUX's ioscan. Unless something's changed, Linux doesn't have the capability to do that yet (the last time I checked, there needs to be some extra functionality added to the kernel SCSI code). Whenever I had to add a device live, there's a thing with /proc/scsi/scsi that you can do (this is from the SCSI Programming HOWTO): Dynamically insert and remove SCSI devices If a newer kernel and the /proc file system is running, a non-busy device can be removed and installed 'on the fly'. To remove a SCSI device: echo "scsi remove-single-device a b c d" > /proc/scsi/scsi and similar, to add a SCSI device, do echo "scsi add-single-device a b c d" > /proc/scsi/scsi where a == hostadapter id (first one being 0) b == SCSI channel on hostadapter (first one being 0) c == ID d == LUN (first one being 0) There's also a script which tries to automate this kind of stuff: http://www.garloff.de/kurt/linux/rescan-scsi-bus.sh I've never tried it, but I've seen it mentioned on a few mailing lists that I monitor. -- Randomly Generated Tagline: "Does anyone not understand what the hell is going on?" - Prof. Bagchi

Nov. 28, 2001

Re: [Wlug] Forcing scsi probe on the fly...

by Charles R . Anderson

On Wed, Nov 28, 2001 at 01:50:01PM -0500, Keller, Tim wrote: Tim.Keller> Does anybody know with Redhat 7.1 (using 2.4.2-2) if theirs a way to force Tim.Keller> the scsi chain to rescan its bus (without an unload/reload) of the module?

Nov. 28, 2001

Forcing scsi probe on the fly...

by Keller, Tim

Does anybody know with Redhat 7.1 (using 2.4.2-2) if theirs a way to force the scsi chain to rescan its bus (without an unload/reload) of the module? so far, I haven't found something like HPUX's ioscan. Thanks, Tim.

Nov. 28, 2001

linuxconf/7.1?

by Bill Mills-Curran

I put together a RedHat 7.1 machine recently and was surprised to find that linuxconf was not part of the default installation. It's clearly improved over older versions of linuxconf, so why isn't it installed? Anyone know why? Thanks, Bill

Nov. 28, 2001

Re: [Wlug] Cable or Good DSL ISP's

by Mike Frysinger

doing like the Roaring Penguin's FAQ and modifying the MTU value for the packets gives me a semi 'real' connection ... of course i have to do some hacks for ident support, but other than that, just about everything has been flawless w/out 'mysterious packet droppings' well, each to their own ;) -mike ----- Original Message ----- From: "Charles R . Anderson" <cra(a)WPI.EDU> To: <wlug(a)mail.wlug.org> Sent: Tuesday, November 27, 2001 03:24 PM Subject: Re: [Wlug] Cable or Good DSL ISP's > On Tue, Nov 27, 2001 at 02:10:53PM -0500, Mike Frysinger wrote: > vapier> i dont know about the 'performance problems' you speak of > vapier> when using PPPoE + NAT ... im running 2 linux boxes as routers > vapier> on verizon DSL and both get a constant 60kB (which is what > vapier> the cap is for my price package). each box does NAT for > vapier> 4-5 people, and each has hit 40+days of uptime w/out any > vapier> 'performance problems' ... > vapier> -mike > > PPPoE's MTU is 1492 bytes due to the extra PPP header in the Ethernet > frame. Hosts sitting behind a NAT will not know of this reduced MTU and > still send IP packets that fill up the Ethernet frames up to a maximum > size of 1500 bytes. (WinPoET reduces the MTU for the local machine where > it is installed.) When the NAT tries to forward these packets, they will > need to be fragmented at the point where they enter the PPPoE link. This > causes reduced performance, and in some circumstances can cause packets > to be dropped on the floor. Normally, Path MTU discovery should take > care of discovering the minimum MTU on the complete path from the source > to the destination, but many incorrectly configured routers/firewalls on > the Internet drop all ICMP traffic, causing mysterious connectivity loss > to destinations behind these broken firewalls due to the failure of the > Path MTU to work correctly. > > You could work around this problem by changing the MTU on all your boxes > behind the NAT/PPPoE (this involves changing a registry key on Windows), > or by using a hack that "clamps" the TCP MSS (Maximum Segment Size) at > the NAT. rp-pppoe, for example, has a built-in feature that does this > clamping. Older pppoe packages for Linux used a kernel module called > mssclampfw to do the clamping. This clamping only works for TCP, > though. > > If you can live with the limitations and hacks required for PPPoE and > NAT, fine. I prefer a "real" connection to the internet. > > -- > Charles R. Anderson <cra(a)wpi.edu> / http://angus.ind.wpi.edu/~cra/ > PGP Key ID: 49BB5886 > Fingerprint: EBA3 A106 7C93 FA07 8E15 3AC2 C367 A0F9 49BB 5886 > _______________________________________________ > Wlug mailing list > Wlug(a)mail.wlug.org > http://mail.wlug.org/mailman/listinfo/wlug >

Nov. 27, 2001

Re: [Wlug] Cable or Good DSL ISP's

by Frank Sweetser

On Tue, Nov 27, 2001 at 05:17:26PM -0500, Mike Frysinger wrote: > doing like the Roaring Penguin's FAQ and modifying the > MTU value for the packets gives me a semi 'real' connection ... > of course i have to do some hacks for ident support, but > other than that, just about everything has been flawless w/out > 'mysterious packet droppings' At least, none that you know of (tcp is quite good at dealing with ocasional dropped packets). -- Frank Sweetser fs at wpi.edu, fs at suave.net | $ x 15 Full-time WPI Network Tech, Part time Linux/Perl guy | ..you could spend *all day* customizing the title bar. Believe me. I speak from experience." (By Matt Welsh)

Nov. 27, 2001

Re: [Wlug] Cable or Good DSL ISP's

by Charles R . Anderson

On Tue, Nov 27, 2001 at 02:10:53PM -0500, Mike Frysinger wrote: vapier> i dont know about the 'performance problems' you speak of vapier> when using PPPoE + NAT ... im running 2 linux boxes as routers vapier> on verizon DSL and both get a constant 60kB (which is what vapier> the cap is for my price package). each box does NAT for vapier> 4-5 people, and each has hit 40+days of uptime w/out any vapier> 'performance problems' ... vapier> -mike PPPoE's MTU is 1492 bytes due to the extra PPP header in the Ethernet frame. Hosts sitting behind a NAT will not know of this reduced MTU and still send IP packets that fill up the Ethernet frames up to a maximum size of 1500 bytes. (WinPoET reduces the MTU for the local machine where it is installed.) When the NAT tries to forward these packets, they will need to be fragmented at the point where they enter the PPPoE link. This causes reduced performance, and in some circumstances can cause packets to be dropped on the floor. Normally, Path MTU discovery should take care of discovering the minimum MTU on the complete path from the source to the destination, but many incorrectly configured routers/firewalls on the Internet drop all ICMP traffic, causing mysterious connectivity loss to destinations behind these broken firewalls due to the failure of the Path MTU to work correctly. You could work around this problem by changing the MTU on all your boxes behind the NAT/PPPoE (this involves changing a registry key on Windows), or by using a hack that "clamps" the TCP MSS (Maximum Segment Size) at the NAT. rp-pppoe, for example, has a built-in feature that does this clamping. Older pppoe packages for Linux used a kernel module called mssclampfw to do the clamping. This clamping only works for TCP, though. If you can live with the limitations and hacks required for PPPoE and NAT, fine. I prefer a "real" connection to the internet. -- Charles R. Anderson <cra(a)wpi.edu> / http://angus.ind.wpi.edu/~cra/ PGP Key ID: 49BB5886 Fingerprint: EBA3 A106 7C93 FA07 8E15 3AC2 C367 A0F9 49BB 5886

Nov. 27, 2001

Re: [Wlug] Cable or Good DSL ISP's

by Mike Frysinger

i dont know about the 'performance problems' you speak of when using PPPoE + NAT ... im running 2 linux boxes as routers on verizon DSL and both get a constant 60kB (which is what the cap is for my price package). each box does NAT for 4-5 people, and each has hit 40+days of uptime w/out any 'performance problems' ... -mike ----- Original Message ----- From: "Charles R . Anderson" <cra(a)WPI.EDU> To: <wlug(a)mail.wlug.org> Sent: Monday, November 26, 2001 10:59 AM Subject: Re: [Wlug] Cable or Good DSL ISP's > On Mon, Nov 26, 2001 at 10:26:15AM -0500, Keller, Tim wrote: > Tim.Keller> I've had really good luck with Verizon DSL (get about 70-80k a second + no > Tim.Keller> down time). In Worcester you might want to check out Speakeasy. A couple > Tim.Keller> people in WLUG use them and are happy. > > Yuck. Verizon uses PPPoE, a broken-by-design protocol (sort of like > PPTP, which is also broken by design). You will have performance > problems if you try to use NAT with PPPoE due to the reduced MTU. > > I also highly recommend Speakeasy. They are best-of-breed as far as DSL > companies go. > > -- > Charles R. Anderson <cra(a)wpi.edu> / http://angus.ind.wpi.edu/~cra/ > PGP Key ID: 49BB5886 > Fingerprint: EBA3 A106 7C93 FA07 8E15 3AC2 C367 A0F9 49BB 5886 > _______________________________________________ > Wlug mailing list > Wlug(a)mail.wlug.org > http://mail.wlug.org/mailman/listinfo/wlug >

Nov. 27, 2001