Connecting WWAN Modem in Linux

As of this writing Linux support about this type of modem isn’t really good. GUI Network Manager doesn’t know such device. You need to configure it manually (in console). The solution that works for me.

$ echo -e “AT^NDISDUP=1,1,\”your_APN_name\”\r” > /dev/ttyUSB0

This command will connect the stick to LTE network.

– You have installed usb_modeswitch package
– the modem created /dev/ttyUSB0
– your modem has no qmi and no mbim. It just works with AT command.


$ su -c dhclient wwan0

This command will acquire IP address for the wwan0 interface.

Various notes:
– When this device connected to internet, your network manager software will recognized the connection as ‘Wired Connection’.
– if your WWAN modem is QMI device, you probably need to use qmcli to configure your device.
– if your WWAN modem is MBIM device, you probably need to use mmcli to configure your device.

How to enable broadband connection with Huawei E3372h on Ubuntu Server
How To Use LTE modem in QMI mode for WAN connection
What is libqmi?
What is libmbim?


Using dd to Create a Bootable USB Linux System from .iso File

This short tutorial assumes you build the bootable USB from a Linux system (not from Windows or Mac).
– First make an hybrid ISO from your distro .iso file using isohybrid tool. This step isn’t required if your .iso  are already a hybrid.

$ isohybrid your_iso_file.iso

You might see an error when issuing the command

Warning: more than 1024 cylinders (1620).Not all BIOSes  will be able to boot this device

Don’t worry about it.The warning refers to very old BIOSes.

– Then use dd to write that hybrid ISO to your USB drive.

$ dd if=your_iso_file.iso of=/dev/sdX

Replace the your_iso_file with the name of your .iso file.
Replace the /dev/sdX with the path to the USB drive. Note: the path to the USB drive (/dev/sdX) you want to write to must not contain a partition letter.  So it should look like /dev/sdb not /dev/sdb1.
Also, the dd command does not provide indicator for progression while it is running in the console. Just wait for a little while.

Create USB Boot Stick | PCLinuxOS forum
HOWTO: Create a bootable Linux Media using the dd Command |

Common Misunderstanding about ZFS

ZFS is an advanced file system and storage management technology. Using ZFS makes you easy to manage multiple storage devices (usually hard drives), create file system snapshots, work with RAID configurations and mirror disks.

Some common myth about ZFS:

ZFS is designed exclusively for enterprise level hardware, particularly machines with ECC RAM and a lot of memory

Truth: You can run ZFS storage pools on machines with very little RAM and there is no need to use a particular type of RAM. ZFS file system can be run just about anywhere, including on cheap consumer machines with less than 1GB of memory. The ECC RAM suggestion only applies to enterprise environments with strict integrity requirements where the strongest data integrity guarantees are required. Note that data corruption can happen under any file system, there is nothing special about ZFS that would make it more vulnerable to corruption using non-ECC RAM.

As for the amount of memory ZFS requires, many people think ZFS needs a lot of memory because ZFS will aggressively cache data in memory using Adaptive Replacement Cache (ARC). Basically, a computer running ZFS will try to use up to 50% of the computer’s memory (or all RAM, minus 1GB) for caching. On machines with 2GB of RAM, ZFS will use about 1GB. On machines with 16GB, ZFS might use 12GB. But, like any other file system, when the memory containing cached data is required for something else, ZFS frees the memory and gets out of the way, allowing the operating system to repossess the memory. Unfortunately, people tend to see ZFS using a lot of otherwise unused memory and assume ZFS requires that much RAM, rather than realizing ZFS is only using that memory because the memory is not needed by any other processes. ZFS can be tuned to use a smaller percentage of a computer’s memory, so only 30% or 25% of memory will be used for cached data.

ZFS is not stable or ready for use on Linux

Truth: Linux port of ZFS may not have all the features that are implemented on other operating systems but ZFS runs quite well on Linux. In one of BSD Now podcast, two developers from the OpenZFS project state that the Linux port of ZFS lags only a few months behind parity with other operating system ZFS implementations. Continue reading “Common Misunderstanding about ZFS”

Tips on Building Homebrew NAS

Really helpful tips on building NAS system I’ve found on Slashdot.
Start quote.
Lessons learned from my dabbling with FreeNAS (and having hardware failure).
-Use generic HDD controllers that are supported in the box. (Using a 3rd party controller and driver, only to discover that when it reports an error, it becomes unavailable altogether, reboot to start again)
-Understand the features you are using. When I started, I configured a ZFS array with two hot spares, when a couple drives failed, the hot spares didn’t activate, and I was stuck…
-Practice a version migration early on.
-Use a motherboard with ECC Ram if you’re using ZFS, I can’t understate this enough. AMD CPU + ASUS Motherboard seems to be your best bet here for Unregistered ECC memory in terms of bang for the buck.
-Use as much memory as possible… if you can use 32GB of ram, do so.

In general, it was fun while it lasted, right now, I put 4x 4TB drives in my old Synology 409 box, and it’s running okay… I’m going to get one of the 12-drive synology boxes in a few months and test my old drives, putting them all in that moving forward. I really don’t have the time and patience for dealing with a homebrew NAS.

I don’t mean for this to discourage anyone, only pointing out that it’s sometimes far easier to buy an appliance that DIY.

End quote.
FreeNAS 9.3 Released | Slashdot