Archive for January, 2013

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False Transfer Speed in Windows 7

False Transfer Speed in Windows 7

What an incredible transfer speed? Is it an SSD? No. It is a NTFS-formatted Kingston DT-101 G2 USB 2.0 16GB pendrive.

I notice that windows report false transfer speed when copying to a NTFS-formatted pendrive. The issue, however, is not observed when the same pendrive is formatted in FAT32. The speed displayed seems to be reading speed from my SSD into the main memory. This is because the progress bar will stop at the position shown in the screenshot and the final bit of transfer seems to take forever. The whole file is cached in the memory before being written into the pendrive, since the disk cache size is observed to increase significantly during the transfer. At the moment, however, I cannot confirm what is causing the problem because I do not find any similar issue on the internet.

Remove old linux kernels

Posted: January 12, 2013 in System Administration
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When upgrading linux kernel, Ubuntu does not automatically remove previous version of the kernel. Yup, it is good if you keep the previous version, so that if anything crashes (eg: your driver is incompatible with the new kernel), you may revert to the old kernel. However, sometimes the old kernels may accumulate and fill up your disk space. Therefore, if you are running fine on your current kernel, you can choose to remove the old ones to free up some disk space. Here’s how you can do it.

  1. Launch your preferred package or software manager. The new Ubuntu ships with Ubuntu Software Center, so you may use that.
  2. Under installed software, search for linux-image.
  3. Remove all kernels other than your current version. (You may find out your kernel version by executing “uname -r” on the terminal.) Using the screenshot below as example, the current kernel version is 3.2.0-35-generic-pae. So we will remove other kernels, which are 3.2.0-23-generic-pae, 3.2.0-24-generic-pae, and 3.2.0-29-generic-pae. The package ‘Generic Linux kernel image’ needs not be removed because it is just a meta-package to pull in the latest kernel image.
  4. Ubuntu Software CenterThen, under installed software, search for linux-headers.
  5. Do the same as step 3. Remove previous version of the linux headers.
  6. Remove GRUB entries for older kernels.