Server Guide and Blog

Rock Your Linux

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Rewiring Your Optimum Cablevision Connections

Motorola SB5120 Modem
Image via Wikipedia

Cable modems need a strong signal in order to operate properly. The more splitters you pass through successively degrades the signal strength (-3.5dB/splitter). For a while internet service was working fine, but then I would loose the external ip address every no and then. I then investigated the wiring in the house, and it turns out there was silly decisions made. There was a splitter in the basement going to nowhere, with at least 25 feet of cable. I removed the splitter and put in a direct coupler, but the problem persisted. I then moved the modem to the other line split off the main. This required reworking of the entire network and the implementation of a network switch. The minimum amount of splitters, the modem must pass through, is two. The first splitter provides service to downstairs and upstairs. The second splitter provides television to my father tv and the modem. I replaced the second splitter in the sequence, and am moving toward replacing the splitter sending signals to downstairs and upstairs. If I replace the main splitter, which is located outsite, and the problem persists, I will be calling Cablevision for the installation of a completely separate main line coming into the house; this will bypass all splitter and give the maximum signal strength possible.

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Reasonable Backup Routines – Service and Desktop Integrity

The device pictured is a 128MiB PNY Attaché US...

Image via Wikipedia

You should have backups of all your files all the time. For a desktop machine always have a backup of your entire /home partition. Use a cronjob and rsync. Mount a usb drive to the /media directory. Use a cronjob as follows:

1 1 0 0 0 rsync -r /home/user /media/backup/user

The above rsync will recursively transfer all folders and files from the user directory to /media/backup/user directory.

You should have at least 1 backup. You can also implement a raid 1 array in case of a hardware failure, which is highly unlikely but does indeed happen. My configuration involves a usb backup drive, mounted as above, and another machine that I rsync the backup to via the network.

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Windows 7 – Mapped Network Drive – Extremely Buggy

Update: The slowness was completely caused by the .docx format of Word documents. The documents were converted to traditional .doc and the issues were resolved.

When mapping a samba share in Windows 7 there is something very wrong. The shares map the exact same way as in Win vista, and comparable to the method in Windows XP; but the performance is horrible. There is definitely something wrong with mapping network drives resulting in extremely slow communication. This topic comes up because of a recent experience where opening any Word document on the share results in a warning dialog box that the file is not available for read/write access. You can always select the bottom option “notify me when this file is available for read/write”, but who wants to wait to open a file that is not being edited by anyone else.

The file is definitely not open by anyone else. The file is not locked, or read only. There is simply a substantial delay in the ability of Microsoft Word to open open documents stored on samba shares. There is nothing that resolves the issue. Changing channels in the router, and forcing it to be on N, to speed things up, does not resolve anything.

The fix will come as part of a service pack. Its nice that Microsoft Windows is closed source. Now we will have to wait an unknown amount of time for this problem to be address. In the Linux community a bug report would have been filed, and some bored or interested tech guru would have investigated and likely addressed the issue by now!

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VirtualBox Bridge and Tap no Longer Needed – Built in

With recent version of VirtualBox you no longer need to create a bridge and tap to enable host networking. In the settings panel of the virtual machine, select the network tab, and make sure that its set on bridged adapter. VirtualBox automatically creates a virtual ethernet adapter, and bridges it to the network of the host machine.

Bridging to the host network is necessary for the virtual machine to get an ip address from the router. Such a configuration is needed to communicate with the machine from the outside world. Because of this feature virtual machines can server website, and other services. I use my virtual machine to host this website, a visual ftp server, a wiki, and an EyesOS server.

There are other ways to forward individual ports from the host system to the guest, but then the ports on the host machine will not be accessible on the host; they will virtually represent the guest OS thus hindering connectivity with the host machine. There may be instances where this is what is wanted and more information, including instruction, can be found on this previous post.

The following is a screenshot of the network tab in VirtualBox. It had a bridge adapter option that will autobridge the connection to an existing ethernet adapter. Bare in mind that this is the screen from a Linux install of VirtualBox and it might be different in Windows. I remember in Windows you might have the option to create a virtual ethernet adapter, and then you can bridge the connection all in VirtualBox. Nothing needs to be done manually anymore, and everything can be done from within the VirtualBox configuration panels.

Screenshot-Windows XP - Settings

Here is a screen from Windows Vista. Go to the network tab of the virtual machine settings:

Network settings

Then select the attach to drop down menu:

Attach

Then change the attach to, drop down menu, to bridged adapter:

Bridged adapter

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Ubuntu VPN Using Network Manager

If you already have your JanusVM working with your iPhone, you can quickly setup your Ubuntu Laptop to use the VPN also. Give a quick sudo apt-get install network-manager-pptp and viola network manager now supports pptp configuration. Give a reboot, and you can configure the settings. I was having a little trouble with the configuration at first, because I was accustomed to the automatic configuration of the iPhone. In the settings you want to enable peer authentication, and refuse chap. Also I had to disable compression otherwise authentication was failing. Then enable all three encryption options. Save, exit, attempt to connect. Enter the username and password you configured in JanusVM and you should connect just fine :)

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PXE Network Boot VirtualBox

You need host networking enabled to boot via the network. Check here for prerequisite configuration.

VirtualBox is capable of network boot, and is practically indistinguishable in configuration as compared to a real machine. To PXE boot a VirtualBox guest OS open the settings of a guest OS:

VirtualBox Settings

Click the system tab:

System tab

To enable PXE boot you have to configure the following section:

Boot section.

Then use the up and down arrows to set the priority of the network boot feature, as shown above.

Up and Down Arrows

You can create a guest OS that has no hard drive; there is no need for one. In such a configuration make network boot the first on the list. :)

Since you intend to use PXE boot, you may consider setting up a LTSP server.