Nov
28
2008
0

Extra Data Received on Transport in Urgent Mode (MSG_OOB)

While transmitting data in Urgent Mode  at the socket layer:

  • Urgent mode is initiated using send(…, MSG_OOB),
  • Current outgoing queue is longer than MTU
  • Several packets are sent out with the URG flag set.

The Urgent Pointer field in the TCP header is not updated correctly. Instead, it stays the same. (more…)

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Oct
22
2008
0

Jumbo Frames and Nagle’s Algorithm (RFC 896)

I really do not like increasing the MTU that large..Some reasons below… (more…)

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Oct
08
2008
0

Wireless on Dell Latitude D630 with OEL5

I have been referring to linlap for this configuration. The configuration has been made possible via ipw3945 and iwlwifi. To be more precise: (more…)

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Written by in: desktop,linux,mobile,network | Tweet This
Sep
15
2008
1

Xen: How to define the boot order for HVM in vm.cfg

This is done by the boot paramer in vm.cfg.

The switches are:

* floppy (a)
* hard disk (c)
* Network (n)
* CD-ROM (d)

If you use

boot = ‘n’

it will be stuck at PXE boot even if there is no dhcp lease and guest will not attempt boot from the Virtual Disk.

To be able to have an order, you need to concatenate the switches. e.g. if you need to have a boot order like

1. network (n)
2. harddisk (c)
3. cdrom (d)

you need to have

boot=”ncd”

in vm.cfg.

Moreover,

If somehow the TFTP server is not accessible or misconfigured, that will fail
over to “c” aka. disk..

But if the DHCP server is not available, the boot will be stuck in a loop of “No
IP address”. Actually this is not much different from a normal BIOS.. A couple
of Dell systems with IBA (Intel Boot Agent) behaves similarly, but only
providing keystroke options.

I’ll also check the behaviour model of pypxeboot too ..

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Sep
15
2008
0

PXE Boot Config Enterprise Linux

Configuring a PXE boot server

Install required packages:

# yum install bind dhcp system-config-netboot tftp-server

Setup dhcpd:

# vi /etc/dhcpd.conf
ddns-update-style interim;
ignore client-updates;

subnet 10.10.10.0 netmask 255.255.255.0 {

option routers 10.10.10.1;
option subnet-mask 255.255.255.0;
option domain-name-servers 10.10.10.1;
option time-offset 7200;
range dynamic-bootp 10.10.10.10 10.10.10.15;
default-lease-time 21600;
max-lease-time 43200;
next-server 10.10.10.1;
option subnet-mask 255.255.255.0;
option broadcast-address 10.10.10.255;
filename “linux-install/pxelinux.0”;
}

Copy the vmlinuz, initrd.img to /tftpboot/linux-install directory.

Create a default:

# cat /tftpboot/linux-install/pxelinux.cfg/default
timeout 100
default el5u1
prompt 1
display boot.msg
label el5u1
kernel vmlinuz
append initrd=initrd.img
#

Set the boot message:

# cat /tftpboot/linux-install/pxelinux.cfg/boot.msg
Press “Enter” to start or auto 100 seconds …
#

Set disable=no in /etc/xinetd.d/tftp (enable tftp)

Setup the services:
# service xinetd restart
# service dhcpd restart
# touch /etc/named.conf
# service named restart
# service iptables stop (or allow tftp connection in the iptables config)

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