I sent the following email to a colleague who will be teaching
the Linux installation course in HP-Singapore. If you find
anything wrong with the instructions that I sent her, please
post your corrections here. Thanks.
PMana
======
Katherine,
After teaching the HP course, "Linux installation and configuration",
using RedHat 7.1, I would like to make the following recommendations:
1. On many machines (at least three that we tried), the network driver
3c59x is autoloaded during boot time using the load options indicated
in /etc/modules.conf (the "eth0" line), but when the kernel daemon
notices that there is no network activity for some time, this
driver is automatically unloaded from the kernel, causing loss of
network connectivity. An "ifconfig" command shows that "lo" is
the only active network interface, and that "eth0" does not exist.
I suggest the following "fixes":
a. If you want temporary reconnection to the network, just start
networking again, using the init script,
/etc/rc.d/init.d/network start.
The trouble with this fix is that it is temporary, and the kernel
daemon will again unload the network support some time later.
At that time, you can start the network init script again.
Obviously, this can cause a lot of frustration.
b. Modify the "eth0" entry in the /etc/modules.conf file, so that
the 3c59x module is loaded permanently. To do this, you need to
read the man pages for modprobe, insmod, rmmod, and modules.conf.
c. Disable kerneld, the kernel daemon, by compiling a new kernel
with no kerneld support. If you do this, you will not be able
to automatically load support for other modules, and so is not
a good idea.
d. Compile a new kernel that has the network driver (3c59x)
permanently included and not a loadable module. This is the
recommended fix. Do not forget to run lilo to install the
new kernel. Also you need to comment out the "eth0" line
in /etc/modules.conf (a # at the start of the line should do
the trick). This tells the boot time scripts that the network
driver is now part of the kernel and not a loadable module.
I recommend that you use the stock kernel version 2.4.2-X
that ships with RedHat 7.1 when you compile this new kernel.
Using the latest kernel version 2.4.9 breaks some of the
RedHat apps that were compiled against 2.4.2. For example,
NFS might stop working because nfs-utils compiled against
2.4.2 does not work with 2.4.9.
2. The stock sendmail that ships with RedHat 7.1 comes with the
file /etc/mail/sendmail.cf that is configured to support only
localhost mail. You can only send mail to a user on the same
machine, but not across the network to a user on another machine.
You can easily fix this by generating a new sendmail.cf file
that supports smtp across machines.
Look for the sendmail source code, and in the directory ./cf/cf
look for the file tcpproto.mc. Modify this file to your taste.
The recommendations given in ./cf/README should be taken into
account when modifying ./cf/cf/tcpproto.mc. I suggest that you
copy ./cf/cf/tcpproto.mc to ./cf/cf/mysendmail.mc and do your
changes here. Run m4 to produce mysendamil.cf from the
mysendmail.mc file. Then copy mysendmail.cf to
/etc/mail/sendmail.mc. Restart the email service by running
the script,
/etc/rc.d/init.d/sendmail restart
3. The default RedHat 7.1 installation is more secure that RedHat 6.X.
To do this, 7.1 shipped with the more secure xinetd, instead
of the traditional inetd+tcpwrapper. Because of this you can not
find the config file /etc/inetd.conf mentioned in the HP-Linux
manuals. Instead, you have /etc/xinetd.conf and the directory
/etc/xinetd.d containing configuration files for each one of
the services finger, rlogin, telnet, wu-ftd, etc. All of these
services are DISABLED, and so you can not do any of the lab exercises
on telnet, NFS, etc mentioned in the HP-Linux manuals. You have to
explicitly/manually enable each of the services that you need. For
example, to enable telnet, edit the file /etc/xinetd.d/telnet
and change the line "disable=yes" to "disable=no". You might also
need to add a line to enable telnet to individual ports like
23(login), 25(mail), 80(http), etc. See "man xinetd" for
additional instructions. After making the changes that you want
to /etc/xinetd.d/telnet, you need to restart the xinetd server
using the script
/etc/rc.d/init.d/xinetd restart.
Good luck. I think that the effort that we make in getting RedHat 7.1
to work with the HP-Linux courseware will pay off in the end.
Regards,
Pablo
_
Philippine Linux Users Group. Web site and archives at http://plug.linux.org.ph
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