Note that you can also use ddrescue to do the same thing, performing a block by block (a.k.a., sector by sector) copy of a source .iso file, writing it to a destination device (like a USB Flash Drive).
Many modern .iso files let you do that kind of thing using either dd or ddrescue.
ddrescue is already installed in Mepis 11 and most earlier releases.
Again, it works the same way as dd, only with different syntax.
For example, you could navigate to the folder that you had the Kubuntu .iso file stored in and do something like this to overwrite a flash drive (sdb in this example, but it may be labeled something else), so that you don't need to use a complete path to it (insert the correct .iso file name in the command).
ddrescue kubuntu-14.04-desktop-i386.iso /dev/sdb
Basically, ddrescue works similar to dd, only you don't need the if= and of= for the input and output devices.
I usually use su to perform operations as root. But, that's probably not really needed.
I'd suggest using fdisk -l and mount commands first, so that you are sure about the media you're writing to/from. For example, like this:
If you make a mistake (for example, use the wrong device for the output, it will be overwritten with the source you use. So, be careful to make sure you've got the correct input/output syntax, using either dd or ddrescue, paying attention to the devices that show up using fdisk -l so you are sure you're writing to the correct device (your flash drive). ;-)
It's also best to make sure the drive you're writing the image to is unmounted (and the location you're using as the source should be mounted). So, if you see a mount point for your destination device (the flash drive you're writing to) using the mount command, unmount any mounted partitions. For example, do this if your flash drive shows up as something like /mnt/sdb1 when using the mount command:
Then, copy the .iso file to it, as shown in previous commands.
Either way (using dd as shown by kmathern), or using ddrescue, will insure the .iso file overwrites the destination device (/dev/sdb in my example) and you'll get an exact copy of the source .iso file from the mounted partition you're copying it from. Many newer .iso files for distros like OpenSUSE, Kubuntu, etc. can be used that way, and are already set up to be bootable using that technique.