Networking at home

I have an Intel SS4200 home storage server running Ubuntu 14.04 server at home, and because the read speeds were only around 60 Mbyte/sec, I decided to do a processor upgrade. After the upgrade I had some problems with the fan, and the speed did not significantly increased. Read more for the details.

In my previous post , I have explained how to setup a 3G/4G modem with USB connection emulating a serial device, in this post I will explain, how to set it up with a modem emulating network connection on the USB interface, like the ZTE MF-821D. The same method applies if you want to use an Android phone as a modem.

Recently I have migrated from my home made NAS server (no-name desktop PC with Ubuntu 1404 Server) to a sweet Synology DiskStation 414 . I this post I will write about the migration process, about how I have migrated from a 10 TB LVM configuration to a 12 TB Raid5 configuration and how I have checked, using md5 hashes, if all files were copied without any error.

In my previous post , I have explained how to upload an OpenWRT image to the MPR-L8 or A5-V11, now we will go trough how to set it up for working as a mini 3G/4G router.

These small routers have a built in telnet service, which can be reached by telneting to the router with your favorite telnet client (e.g. Putty). The user name is admin and if you have not changed the password it is also admin.

If you have one of these modems you may have encountered the problem, that on first try your USB 3G modem is working very well, and later it is not working at all. In this post I will explain a very easy trick, on how to fix this issue.

The MPR-L8 is very nice and cheap mini router, having also an USB port and a built in battery. From the factory it has a very capable firmware, providing support for 3G dongles for mobile internet sharing, media and file sharing from USB devices and compared to its very small size has all the filtering and port forwarding functions, that normal sized routers provide. Unfortunately the factory firmware is not very stable and we may want to add additional functionality like support for 4G modems or use it as an OpenVPN client to connect easily to home network from any location. All this is possible by flashing an OpenWRT firmware and setting it up according to our needs.

Earlier I have measured the speed of some pendrives, now here is the next bunch. They are all 2.0 drives, in some cases the speeds are close to the limit of this interface.

There is an easy way to set the network interface speed in Ubuntu 14.04: In the iface section of the /etc/network/interfaces  you can add the link-speed and link-duplex parameters, to pass them to ethtool. The example below sets the link speed to 100 Mbit/sec: iface eth1 inet static         address 192.168.1.120         netmask 255.255.255.0         network 192.168.1.0         link-speed 100         link-duplex full

In a Samba installation I was trying to set up a Share, where any user without authetication is assigned to a certain Unix user, to have the propper rights ro read the content presented there. After reading the Samba manual, the solution which came to my mind was to do the following setup: guest only=yes guest account=user But this was not working and not globally readable files (which had permission for the user user) were not readables. After reading a bit mode the manual, I found, that guest only is not enough it shoucl always be acompanied with guest ok .  I have tried this also, but still no lock. After a lot of debunning and looking very stupidly, it come to my mind, that let's try to use the force user directive. I have constructed the following setup: guest only = yes guest ok = yes force group = users force user = user and yes, this was working perfectly, the user's permissions were used in the filesystem.

umask is a user related setting in Linux, which specifies, that when creating a new file or directory which permissions will be set. For the shells users can set the umask with the umask command (what a surprice :-) or they can set the defult value using the same command in the shell init scripts. But there are other programs (like Samba), which are using the umask and they are not taking into account the changes what users are making after they have logged in into the system. To change the umask for them as the pam_umask manual says, you need to set the values in the GECOS fields. But what is GECOS? You can find it in Wikipedia , that it is in the /etc/passwd file, but it may be more difficult to find an example for it. To put it short, the GECOS fields are the 5th element in the passwd file and the fields are separated by comas. In the following example we set the umask for the user test: test:x:1003:100:Test user ,umask=0002 :/home/test:/bin/bash

I have created a Share on a Samba server, to be used commonly by several users, with the goal, that all users belonging to a Unix group (in this case "users") can read and write these files, but nobody else should have access to these files. Speaking in unix permissions I wanted to add the 0770 mask to these files. After reading the Samba documentation I concluded that I need to set the "force create mode"/"force directory mode" parameters for this share and this should do the trick. After setting it up it was working well for my account (the first, account created during installation), but it was not working for a second account, which I have created manually, and where I have added it manually to the users group as its primary group. For this account it always omitted the group write attribute for the directories, where the resulting permission was always 0750. After some investigation it turned out that Samba was honoring the "umask" re...

Probably this is nothing new, but I have spent almost one day to figure this out. If you have a computer with preinstalled windows and want to do a clean install, the easies way is to go to http:// windows .microsoft.com/ en-us/ windows -8/create-reset- refresh-media  and create an installation USB pendrive. This has the advantage, that you can create it with EFI secure boot, which is fast and secure. Addition: For Windows 7 you can use the following link: http://www.microsoft.com/en-us/software-recovery

This post is about experiences with hacking into the MPR-L8 and my attempts to install modified firmware to the router. At the end of the post there will be links to the simply uploadable OpenWrt firmware along with the original firmware to be able to restore the router.