Saturday, 30 November 2013

Steam + LMDE + AMD64 + NVidia

To install Steam on 64 bit LMDE with NVidia drivers (already installed) use this command;

sudo apt-get install steam libgl1-mesa libgl1-nvidia-glx:i386

Friday, 29 November 2013

gksu on LMDE

I just installed Linux Mint Debian Edition (LMDE) for a friend and came across a small problem with launching the Mint Software Centre application.

Because the Mint Software Centre allows users to add and remove software it sensibly requires root privileges before you can proceed. To do this it utilises gksu.

Specifically, the launcher in the menu looks like this;

gksu mintinstall

The problem is that when you try to launch the MSC it asks for a password. Entering your user password (which has sudo privileges) does not work. This is because gksu is expecting the root user password, which with a default install does not exist.

The way to fix this is to tell gksu to use sudo for privilege excalation.


This will popup a dialog box like this;

 Change the "Authentication Mode" from "su" to "sudo" and you are done!

Tuesday, 12 November 2013

Using DD to copy a failing drive

I have posted before about copying a hard disk using DD.

This post expands on that concept a bit for situations where you need to do an emergency copy of a failing hard disk.

The scenario:

You boot up your system only to receive a SMART warning that one of  your hard disks is failing and should be replaced.

I currently have such a situation.

The drive in question has a bootable Windows partition as well as non-bootable ext4 partition.

Fortunately, I boot my Ubuntu system from a seperate SSD but if you don't have that option then a LiveCD is your best option. 

So, now I have purchased a replacement hard disk and I'm wanting to copy the old drive over to the new drive to save having to do all the re-installing of Windows/Steam.

I am aware of the potential for file corruption and if I see evidence that corruption has adversely affected things I will go to PLAN B, a complete Windows re-install. I hope I won't have to go that route.

So, I plug the new disk into my system and determine that the failing disk is /dev/sdb and the replacement is /dev/sdc

To copy the disk over I want to use the 'dd' command

dd if=/dev/sdb of=/dev/sdc

This works, but after a bit I hit a bad sector, at which point dd stops copying data. This is not what I want.

To make dd ignore errors and re-sync it's position on the target device once it resumes we can expand on our dd command like this:

dd if=/dev/sdb of=/dev/sdc conv=noerror,sync

That's great. Don't you love Unix?

Anyway, after a while of dd chugging along I decide to check on progress. I open another terminal (you can also background the process and use the same terminal) and enter:

kill -SIGUSR1 `pidof dd`

This produces the following output in the terminal window that dd is executing in:

7382+0 records in
7381+0 records out
56787277824 bytes (57 GB) copied, 1369.35 s, 4.1 MB/s

Good lord. At 4.1MB/s this 1TB drive will take an estimated 2 days to complete!

This is obviously unacceptable.

The problem is that dd uses a default block size that is quite tiny. Of course, this being Unix we can control that.

I stop the dd process and re-issue the command, this time specifying a 4M block size:

dd if=/dev/sdb of=/dev/sdc conv=noerror,sync bs=4M

Now, when I check the progress I see a much more satisfying result:

37382+0 records in
37381+0 records out
156787277824 bytes (157 GB) copied, 1369.35 s, 114 MB/s

144 MB/s, that's more like what I want. The re-image should now take a matter of hours rather than days.