Mark's Linux Tips and Notes

Some notes that you might find useful. Note that I'm a Red Hat type. You may also be interested in some scripts that I use.

You can get rid of these in /var/log/messages:
Feb  6 17:33:01 pacific modprobe: modprobe: Can't locate module sound-slot-1
Feb  6 17:33:01 pacific modprobe: modprobe: Can't locate module sound-service-1-0

with this:
# No 2nd sound card
alias sound-slot-1 off
alias sound-service-1-0 off
 
in /etc/modules.conf

apparently some kde stuff and the flash plug in try for more than one sound card which is what is generating the error messages.

If your fiancee uses OS9 on her old Mac as mine does, you will want to check out the work of the fine people at wamcom.org. They have got a build of Mozilla for OS9 up and running and nicely packaged for installation. A real browser for an otherwise obsolete system. The wild eep will live on a few more months.
In order to get the CGI variables DATE_GMT, DATE_LOCAL and LAST_MODIFIED to be set to a non-empty value under Apache 2.0.47-10 as packaged with Fedora Core 1, I had to add
```
 -->
```
to all of my html pages before including the cgi scripts. Otherwise, the environment variables were defined, but not set to anything. I gave up on trying to find the root cause.
To get the macromedia flash plugin working on fedora core 1, you need to install compat-libstdc++-7.3-2.96.118.i386.rpm.
'make install' on the Fedora systems will set grub up to use an initrd. If you do this with a Linus 2.6 kernel, you will often see this error when trying to use the initrd:
```
VFS: Cannot open root device "LABEL=/" or unknown-block(0,0)
Please append a correct "root=" boot option
Kernel panic: VFS: Unable to mount root fs on unknown-block(0,0)
```
The most common advice given is to change your grub entry to something like root=/dev/hda2.
What most of the other posts on this topic don't include is the preceeding messages:
```
kernel: checking if image is initramfs...it isn't (no cpio magic); looks like an initrd 
kernel: Freeing initrd memory: 98k freed
kernel: RAMDISK: Compressed image found at block 0
kernel: RAMDISK: incomplete write (-28 != 32768) 4194304
```
The root of the problem is that the default ramdisk size of 4096 is not big enough for the initrd used on Fedora. I presume the same problem exists on other systems.
Increasing your ramdisk size to 8192K will fix the problem. The config item is CONFIG_BLK_DEV_RAM_SIZE and it can be found under device drivers, then block devices in the configuration menus.
```
[mjfrazer@arctic linux-2.6.6]$ egrep 'INITRD|RAM_SIZE' .config
CONFIG_BLK_DEV_RAM_SIZE=8192
CONFIG_BLK_DEV_INITRD=y
[mjfrazer@arctic linux-2.6.6]$ 
```
After hurting my brain for the n^th time about endianness woes with bitfields, I wrote down some notes on the subject.
I have an ibook running OSX that I sometimes plug into the ethernet and sometimes use on an 802.11 network. Since there are two separate MAC addresses for this device, I have two hostnames for it in my DHCP configuration. Sometimes the hostname on the ibook gets messed up and the hostname command will return two lines:
ibook.mjfrazer.org
ibook-eth.mjfrazer.org
which are the two names configured in my DHCP server. This causes my ssh X forwarding to get messed up. It generates the error
Warning: No xauth data; using fake authentication data for X11 forwarding.
Su'ing to root and running 'hostname ibook.mjfrazer.org' fixes it up. Note that every time you start X11.app, you get new xauth data, so you may need to restart X11 after you fix up the hostname.
When using the GatewayPorts option in my .ssh/config to hosts I would see a
```
bind: Address already in use
```
error for each LocalForward in my config. When I stopped using the FC distro kernel due to hangs with my Matrox G400 and my Via rhine based ethernet cards, I stopped seeing this error message. I reckon that it was due to the FC distro kernel enabling both IPv4 and IPv6, and the sshd trying to bind to 127.0.0.1 and :::::001 (or whatever the localhost address is in IPv6) at the same time.
I recently set up dual Dell 2005FPW displays on my FC4 box and ran into some configuration problems with xorg.conf. The BusID of the primary (AGP) controller (I run two ATI 7000's, one AGP and one PCI) was not being set in xorg.conf. I filed a bug against Fedora describing the fix, which you can view here
On my second display, I have hooked up a second computer to the VGA port since the dell displays have both DVI and VGA inputs. There is a single button on the front panel to switch inputs, no OSD menu driving as was needed on my old viewsonic P810. Anyways, the xorg-x11 on FC4 needed a modeline for driving the display at 1680x1050 which system-config-display did not add. I filed a bug against fedora describing the fix, which you can view here