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How to Resume Partial File Transfers

I work primarily with UNIX and Linux machines and scp is my main choice to transfer files with. It is both convenient, short and secure.

Example:

scp localfile user@remotecomputer:/path/to/target/dir

Recently I was transferring an 8GB file and due to a network issue, the transfer was interrupted at nearly 40%.

I found a solution at joen.dk ,which uses rsync to resume the transfer:

rsync --partial --progress --rsh=ssh host:remote_file local_file

Now we can improve this slightly by shortening the above command. We can substitute –rsh=ssh with -e ssh, and use -P instead of –partial –progress. Also, you can add user@host if you need to specify a different remote shell user:

rsync -P -e ssh user@host:remote_file local_file

This above example will work with any file that was partially transfered. How the transfer was started does not really matter. It could be through scp, nc or even ftp. After you execute the above command it will take rsync a little time to verify the previously downloaded part before it continues with the rest. Be patient, depending on your network speed rsync could take some time to go through what you have already transfered. Of course this is much faster than if you were to start the download all over again and it shows you the progress in percentages.

Keep in mind that there have to be a couple of requirements in place in order to resume the file transfer with rsync:

1. You should have remote shell access.
2. The remote machine should have rsync installed. Since rsync is by default on most Linux distributions that generally should not be an issue.

Convert Quicktime Movies to AVI encoded with MPEG-4 (MOV to AVI) with Linux/Ubuntu

A lot of camcorders record in the .mov (Quicktime) format. It has high quality video and depending on the underlying codec it provides a good compression, but it is too proprietary and very often you might not be able to play it on different devices.

AVI on the other hand is more widely accepted format. AVI, like MOV, is a media container that envelops encoded media. In this example we will convert Quicktime video (.mov) to .avi that contains media encoded with mpeg-4.

If you want to preserve the original quality and resolution with pcm_u8 (analog 8bit) audio:

ffmpeg -i inputfile.mov -sameq -vcodec msmpeg4v2 -acodec pcm_u8 outputfile.avi

Obviously I would prefer something better for the sound so I normally use the mp3 as an audio codec. To do this make sure that you have the libmp3lame0 package installed to do that:

sudo apt-get install libmp3lame0

And then:

ffmpeg -i inputfile.mov -sameq -vcodec msmpeg4v2 -acodec libmp3lame outputfile.avi

If you want to change the resolution then add the -s option and specify the horizontal and vertical resolution. Make sure to preserve the original aspect ratio:

ffmpeg -i inputfile.mov -s 960x540 -sameq -vcodec msmpeg4v2 -acodec libmp3lame outputfile.avi

Broadcom Wireless Chipset (BCM4311, BCM4312, BCM4321, and BCM4322) on Ubuntu Karmic.

If you have a Broadcom wireless chipset BCM4311, BCM4312, BCM4321, or BCM4322 it will not work with Ubuntu Karmic after an upgrade or an install.

To get it working, you need to install the STA driver. You can get it from the Broadcom site:

http://www.broadcom.com/support/802.11/linux_sta.php

Follow the instructions in the README.txt file which is on same page.

After you have finished installing it the wireless will work, but only until the next reboot. To make this permanent follow these steps:

1. Run:

sudo rmmod ssb

For some reason you cannot blacklist the ssb module. It always runs on boot even if it is in the blacklist.conf file.
After that you need to run this to get rid of the ssb module permanently:

sudo update-initramfs -u

2. Now that we got rid of ssb, we need to make sure that lib80211 is loaded on boot. To do that add lib80211 to the end of the /etc/modules file:

echo "lib80211" | sudo tee -a /etc/modules

I went ahead and added wl to it as well:

echo "wl" | sudo tee -a /etc/modules

So the /etc/modules file looks like this:

# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.
lp
rtc
lib80211
wl

3. Now we need to make sure that “insmod wl.ko” as specified in the README.txt file runs every time we boot. There might be a better way to do this but I just added it to the /etc/rc.local file.

Before I did this I copied the wl.ko file to the /lib/modules/2.6.31-14-generic/kernel/lib directory. This way we can get rid of the source files we downloaded from the Broadcom site along with the binaries we compiled and not worry about losing the wl.ko file:

sudo cp wl.ko  /lib/modules/2.6.31-14-generic/kernel/lib

Then add the line “insmod /lib/modules/2.6.31-14-generic/kernel/lib/wl.ko” at the end of the rc.local file, right above the exit 0 line:

sudo gedit /etc/rc.local

Here is how the rc.local file looks:

cat /etc/rc.local

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

insmod /lib/modules/2.6.31-14-generic/kernel/lib/wl.ko
exit 0

4. Last step is to pin down the linux kernel so that we don’t upgrade the kernel accidentally along with the other updates:

System -> Administration -> Synaptic Package Manager

Then click on the “Status” button and select “Installed”. Then search for “linux-”. Select all packages that start with “linux-” and then Package -> Lock Version.

When a Linux User Buys Apple

I just came upon two articles by Thomas Driemeyer. The author seems to be very sincere in his attempt to describe his experiences in switching from Linux to Apple (and subsequently back) and his good sense of humor makes the reading pleasant and amusing:

When a Linux user buys Apple’s Mac mini

When an Apple Mac mini user gets disenchanted

Clone Disk Drives with Ubuntu. Make an Exact Copy of Your Hard Drive.

Before I start, I would like to clarify that this step by step tutorial applies not only to duplicating hard drives that have Linux OS on them. You can clone pretty much any drive. What is on the hard disk is irrelevant; it could be Windows, Mac OS, Linux, just data, etc. There have to be just a few basic things in place:

1. The target drive should be the same size or bigger than the source disk drive.
2. Have a Linux Live CD or a Linux bootable USB drive or some other way of booting into Linux (we will be using Ubuntu’s Live CD for this tutorial).
3. Access to the internet.
4. There is a presumption that you know how to install a hard drive.

Making an exact copy of a hard drive (or any drive for that matter – CD, DVD, USB, etc.) is very easy and quick with Linux. One of the most popular commands on Linux to do this is dd. It is a very powerful utility that was originally developed for the UNIX operating system and is now default on every Linux distribution. It does a bit for bit copy of the data and it does not care about cylinders, partitions or files. Here is an example of a dd command that would make an exact copy of one disk to another:

dd if=/dev/sda of=/dev/sdb bs=64k

The bs option specifies the block size and it could be omitted, but it would speed up the process since the default block size is only 512 bits. dd is very effective and powerful command but it is not very suitable when you are trying to make a copy of a failing or failed disk. dd is not designed to read and recover bad sectors.

There are a number of other open source programs developed since dd (dd variants) that would address situations where there might be some bad drive sectors and they perform faster and more efficient than dd. Some of those are: dd_rescue, dd_rhelp and GNU ddrescue. GNU ddrescue is the one that I would recommend using if you want to clone a drive. It works both for a perfectly good drives that you would like to clone and for failed drives that you would want to recover data from.

Install the new drive.

The new drive should be of the same or bigger size. You might have to get the BIOS to recognize the new disk; in most cases that is not necessary. After you have put the drive in, boot into Linux from another device. An Ubuntu Live CD would be perfect for that. You can download an ISO image from here.

Now you have to find out what the drives’ logical names are. Open up a terminal window: Accessories -> Terminal or Alt + F2, then type in gnome-terminal and hit Enter.
In the terminal window type sudo lshw -C disk:

sudo lshw -C disk
  *-disk:0
       description: ATA Disk
       product: WDC WD400BB-75FJ
       vendor: Western Digital
       physical id: 0
       bus info: scsi@0:0.0.0
       logical name: /dev/sda
       version: 14.0
       serial: WD-WMAJA3488275
       size: 37GiB (40GB)
       capabilities: partitioned partitioned:dos
       configuration: ansiversion=5 signature=000b280f
  *-disk:1
       description: ATA Disk
       product: ST340016A
       vendor: Seagate
       physical id: 1
       bus info: scsi@0:0.1.0
       logical name: /dev/sdb
       version: 3.75
       serial: 3HS63J2C
       size: 37GiB (40GB)
       capabilities: partitioned partitioned:dos
       configuration: ansiversion=5 signature=000b280f
  *-cdrom:0
       description: SCSI CD-ROM
       physical id: 2
       bus info: scsi@1:0.0.0
       logical name: /dev/cdrom
       logical name: /dev/scd0
       logical name: /dev/sr0
       capabilities: audio
       configuration: status=nodisc

In my case I have two disks- disk:0 and disk:1. The logical name of disk:0 is /dev/sda and the one for the second disk is /dev/sdb. Make a note of that. In your case that might be different. Identify which drive will be the source and which one the copy. There are 2 things in the above output that will help you do that- the product and the size. You can also use the command sudo fdisk -l. It will show you the hard drives and their partitions.

Prepare the target drive.

Now that you have identified the target drive you need to put an initial partition on it. In the terminal window you have opened execute:

cfdisk -z /dev/sdb

The cfdisk program will start, then type W and then yes to confirm. This is simple enough but you could also use the GParted program that comes with Ubuntu to do the same.

Install the GNU ddrescue program

Before you can install ddrescue you need to enable the Universe Software Repository. Go to System -> Administration -> Software Sources and then check the box next to “Community-maintained Open Source software (universe)“. Close the window. It will ask you to whether you want to refresh the list of software- go ahead and agree to that. After it finishes you can install ddrescue by running this in the terminal window:

sudo apt-get install gddrescue

Clone the disk.

Now you are ready to clone the drive by executing ddrescue. Specify the source disk first and then the target disk. You can use the -v option to be able to see the progress of the operation:

sudo ddrescue -v /dev/sda /dev/sdb

Make sure you get the order of the drives right or you could overlay the old drive with the new drive and loose all the data!

Depending on the size of your source drive this operation could take a couple of hours or even more. Once it finishes the new drive will be an exact copy of the old one. You can run a quick check on the file systems of the new drive:

e2fsck -fp /dev/sdb1

If the new drive is bigger than the old one you need to extend the partition(s) on it or create another one to make use of the rest of the space. The GParted program that comes with Ubuntu is ideal for this.

Once you are done, remove the old drive and boot from the new disk.

Credit: Ubuntu Kung Fu. Published article from the book.