Red Hat AS 4 questions

Rick Stevens rstevens at vitalstream.com
Wed Aug 10 22:06:47 UTC 2005


Allen, Jack wrote:
>         I just loaded Red Hat AS 4 on and IBM xServer 366. Everything 
> when fine. I have 2 disk in Raid 1, that everything was loaded on and 
> appear as /dev/sdg1 - /dev/sdg9. Then there are 12 other disk, that are 
> in Raid 1, so the OS sees 6 disk. These 6 disk were all setup with one 
> partition and appear as /dev/sda1 through /dev/sdf1. I ran pvcreate 
> /dev/sda1, pvcreate /dev/sdb1 ... Then I ran vgcreate vg01 /dev/sda1 
> /dev/sdb1. The vgdisplay command shows the correct information, no 
> problem. Then I ran
> 
> lvcreate -L 2G -n h0000n0.v00a vg01. This is for and application to 
> directly access, so I needed to change the owner, group and mode. So I 
> went to /dev/vg01 and did "ls -l" to see what it currently was. This is 
> when I found out the name h0000n0.v00a was a symbolic link to 
> /dev/mapper/vg01-h0000n0.v00a. So my first question is: does this mean I 
> am running the dev file system or something by default? Or is this the 
> way that lvm2 works now?

RH AS4 is a 2.6 kernel, unlike AS3 and 2.1, which were 2.4 kernels.
The 2.6 kernel uses "udev" to manage device names and such.  What you're
seeing is how udev does things.  Check the man pages for udev.

>         Now to my second problem. When I loaded Red Hat AS 3, I don't 
> remember doing anything special to create the /dev/st* and /dev/nst* 
> nodes. It seems there was something like 7 of each. Well on the this 
> system there are none. The man page for st gives an example of "mknod -m 
> 0666 /dev/st0 c 9 0", which I did. No errors. But if I do "mt -f 
> /dev/st0 status" the error indicates no such device or address. I would 
> assume this is because the major device number may not be correct. So my 
> question is: what should it be? Or is it related to the /dev/mapper 
> question above? As far as the tape drive really being connected to the 
> system, it shows up during boot when the controller is identified. This 
> is before Linux boots. I don't remember if it showed up during the Linux 
> boot. I will have to reboot again to see. I guess another question would 
> be is all the boot messages from the kernel logged somewhere? I thought 
> it was, but don't remember where.

If you check /var/log/boot.log, you should see where the device was
identified and assigned a name.  You'll probably find it listed as 
"/dev/tape*" rather than "/dev/st*".  Again, this is udev doing its
thing and you should familiarize yourself with it.

The 2.6 kernel is a radical departure from what you're used to.  It's
a better kernel, it's faster, it's cleaner and it handles memory much
better.  You'll like it, but there is a bit of a learning curve.
----------------------------------------------------------------------
- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-  You know the old saying--any technology sufficiently advanced is  -
-               indistinguishable from a Perl script                 -
-                                 --Programming Perl, 2nd Edition    -
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