Wikipedia:Reference desk/Archives/Computing/2011 February 18

= February 18 =

Good Alternatives to file and folder shortcuts on a USB flash drive?
When trying to keep track of hundreds of files on a USB flash drive, I usually organize the files into a tree structure with folders named after topic or theme. I use quite a lot of folder and file shortcuts back and forth between the various folders.

It works fine until I plug my portable USB drive into another computer where it suddenly no longer is called "E:\", but instead "G:\" or "I:\" or whatever. This renders all my file shortcuts useless. ;-( Of course, the same thing also happens when I copy a directory tree to another disk.(I currently use WindowsXP but I would like the solution to be platform independent).

Could you please give me some advice or ideas to how I might solve or avoid this problem? --Seren-dipper (talk) 13:42, 18 February 2011 (UTC)


 * The easiest thing to do might just be to a pick a drive letter that's not in use on the computers you usually use and then change the USB drive to that letter (Control Panel -> Administrative Tools -> Computer Management -> Disk Management or just Start->Run->diskmgmt.msc). Of course that won't work if you go to a computer that has the drive in use, but if you use the same computers regularly this could be the easiest solution.  ZX81    talk  14:41, 18 February 2011 (UTC)
 * Or you could use subst to create a substitute drive letter of your choice on the computer which maps to the usb drive letter. There's a nice gui version here which is portable too so you could keep it on your usb drive ready to use on any computer. Both methods probably require admin privileges on the computer you use them on, so might not work on public or restricted computers. 82.43.92.41 (talk) 14:48, 18 February 2011 (UTC)

Great answers! Thank you! --Seren-dipper (talk) 19:46, 18 February 2011 (UTC)

How may I "update" file shortcuts?
Now, do you have any suggestions for how I may "update" drive letter and/or path for all file and folder shortcuts when (or after)  moving a directory (including all subdirectories) into a new drive and/or into another location within the directory tree structure? --Seren-dipper (talk) 19:46, 18 February 2011 (UTC)

Identifying disks on Linux, similar question to the above
The question above about USB drives on Windows made me think that the same kind of thing would happen on Linux. Linux identifies drives in the order it finds them, assigning them labels such as,   and so on. My current computer has two internal hard drives, so a USB drive would be. But suppose I added a third internal hard drive - this would cause USB drives to become  instead, causing the ready-made mountings in   to become useless for this purpose. Is there some way in Linux to mount filesystems by the actual disks they're on, not by the device Linux happens to assign them? J I P &#124; Talk 14:32, 18 February 2011 (UTC)
 * On my (Ubuntu) system, there are automatically constructed symlinks in, so that you can talk about your partitions by what they're labeled, rather calling them  .  Ubuntu also automatically handles mounting (also using labels) in some magical fashion I don't understand, so I've never had to touch my  .  Paul (Stansifer) 15:13, 18 February 2011 (UTC)


 * In Fedora and Redhat, I have /dev/disk/by-id, by-label, by-path, and by-uuid. So, there are many options for identifying a disk other than using the sdx option. However, as Paul stated, Linux auto-mounts removable media by itself, so there is no need to add USB drives to fstab. -- k a i n a w &trade; 16:15, 18 February 2011 (UTC)
 * Minor quibble: I don't believe "Linux" (the kernel) performs any auto-mounting. gnome-volume-manager, which is running by default in Ubuntu and many other Linux distributions, auto-mounts disks.  If you use Kubuntu, a different mount service manager may be running; and if you use a different version of Linux, you might not have any auto-mounting functionality at all.  Nimur (talk) 16:43, 18 February 2011 (UTC)


 * As Kainaw notes, partitions can be mounted by UUID. They appear in /dev/disk/by-uuid, and you can (I guess, I've never used that method) specify that explicitly in fstab. An alternative is to use the UUID= syntax in fstab, which does the same thing.  So my own fstab looks like this:

# boot partition UUID=40cdfe04-298a-4ac6-919c-11c88e451a06 /              ext3    relatime,errors=remount-ro 0       1 # swap UUID=8c3f96ba-e5f6-4a52-9162-fe33a7d077b2 none           swap    sw              0       0


 * This survives all kinds of disk rearrangements. Because the UUID corresponds with the partition (not the physical disk) one can dd a drive's contents to a bigger drive, unplug the old, and the system boots as before, with no change to fstab. -- Finlay McWalter ☻ Talk 17:05, 18 February 2011 (UTC)


 * The manual page for mount(8)</tt> recommends the UUID= method over the /dev/disk/by-xxx method. -- Finlay McWalter ☻ Talk 17:13, 18 February 2011 (UTC)

Installing Fedora 14 with every single package?
Suppose I were to install Fedora 14 64-bit version with every single package that comes on the install DVD. Roughly how much space would that take on the install partition? J I P &#124; Talk 17:14, 18 February 2011 (UTC)
 * My vague guess/memory is in the 6-8 gb range. The dvd is something like 3.3gb but a lot of the content is compressed.  You'll want to install more stuff beyond the dvd, though, and have some space left for swap and user files.  71.141.88.54 (talk) 11:25, 19 February 2011 (UTC)
 * OK, so that probably won't be a problem. I have a 80 GB root partition, which I'm currently only using about 8% of. All of my personal user files are on a separate partition, which is far larger. There's yet another partition for swap. I figure it shouldn't be too much of a problem to upgrade to Fedora 14 by reformatting the root partition but keeping the other partitions intact. J I P  &#124; Talk 14:25, 19 February 2011 (UTC)
 * Keep in mind that you might clobber various kinds of configuration files by doing that, or you might have to re-install programs that you forgot about. I'd advise having a good backup of the root partition before doing the upgrade.   My usual way of upgrading an OS is buy a new hard drive, install OS on it from scratch, copy user files from old drive, and put the old drive in a drawer just in case (more backups are always good). 71.141.88.54 (talk) 20:05, 21 February 2011 (UTC)

Best choice of writeable DVD disc types
I'm in the process of moving a writeable DVD drive from another old computer to the old computer I use. It will be able to write DVD+RW, DVD-RW, and DVD-RAM. Which of these discs would be the best choice to buy and use please? I am going to verify what is written to disc, and it would help if any faults could be corrected. Thanks 92.28.240.53 (talk) 17:15, 18 February 2011 (UTC)


 * Our article DVD+R lists a few ways that DVD+R is allegedly superior to DVD-R, at a cost of being able to store slightly less data. Comet Tuttle (talk) 17:53, 18 February 2011 (UTC)
 * I agree with above statement. If in dault, read the specification. Of course don't forget the "made in China" warning label :-) Electron9 (talk) 18:17, 18 February 2011 (UTC)


 * Electron9's being amusing, but he's correct that there's cheap media and more-expensive media, and I've seen a lot of people online blame cheap media for discs going bad within a short time. Note that our various articles about DVD recordable formats say DVD-Rs and DVD+Rs may have a lifespan as short as a couple of years.  I also note that our DVD-RAM article has claims of superior reliability and length of data storage compared to DVD-R and DVD+R, but I have no experience with DVD-RAM, and that article does need some more citations.  Comet Tuttle (talk) 18:44, 18 February 2011 (UTC)

I didn't ask about DVD-R or DVD+R, but DVD+RW and DVD-RW and DVD-RAM. 92.29.119.194 (talk) 23:45, 18 February 2011 (UTC)


 * It is claimed that DVD+RW has better error-tolerance during the read and write process; for example, see this review from Tom's Hardware. In practice, the distinction is moot.  Use caution with DVD-RAM, because while many DVD drives can read the entire set of DVD-R, DVD+R, DVD-RW, and DVD+RW, fewer drives can read DVD-RAM.  Nimur (talk) 00:04, 19 February 2011 (UTC)


 * (ec) Pressed DVDs and DVD±R[W] all use the same on-disc format for the recorded data. DVD–RAM is completely different. You can't make DVD-Video discs using DVD–RAM. I think that it's far superior as a sector-addressable optical disc format, but the discs are more expensive (you do get more for the price) and most DVD drives can't read them.


 * I think it's true that DVD+R[W] has a more robust method of storing information in the pregroove than DVD–R[W]. But that information is only used when burning the disc. It has no effect on the readability of a 10-year-old disc, but it might have an effect on its rewritability, I suppose. The user data is encoded in precisely the same way on pressed DVDs and DVD±R[W]. DVD+R[W] does not have better error correction for your data, just for the pregroove information.


 * When using rewritable DVDs as sector-based media with a filesystem like UDF, I think DVD+R has advantages over DVD–R because it's erasable in smaller blocks (?). If you're writing and erasing whole discs at once, there's no advantage.


 * The Wikipedia article is obviously a mess. I'm pretty sure that DVD+R doesn't have a smaller capacity than DVD–R by design. Capacity varies slightly between manufacturers, and some random person stuck a couple of random blank discs in their drive and put the reported capacities in the article. -- BenRG (talk) 00:13, 19 February 2011 (UTC)


 * I don't think that's correct. Unlike with CDR, DVD-R and DVD+R commercial disc capacities hardly vary at all AFAIK, at least for single layer variants. DVD-R discs are very slightly larger (~4489MiB or 2,298,496 sectors) than DVD+R (~4483MiB or 2,295,104 sectors), however the capacity differences are so small as to be irrelevant. See also Nil Einne (talk) 13:04, 19 February 2011 (UTC)

To give more context, I'm only interested in data disks, for archiving. So I want something that will still have the data after ten or twenty years in a drawer, and which will be readable when put in most computer DVD drives. What is best for that? Thanks 92.29.119.194 (talk) 00:41, 19 February 2011 (UTC)


 * I recall DVD-RAM being better than DVD+RW but it's also way more expensive last time i checked. Read technology specifications to know for real. Anyway DVD+R is still better than DVD+RW due chemical stability. As for physical discs, Verbatim is likey the most reliable. And extremely vary of rip-offs etc.. very common these days! with products that have the logotype and look of the original but lack any quality. Infact make a software setup so that you can use the writer feature that measure the resulting margin which ends up on the discs. To improve storage you should eliminate the oxygen, humidity and heat. Nitrogen and humidity absorbing materials can be helpfull in this aspect. Electron9 (talk) 04:18, 19 February 2011 (UTC)

Is DVD-RAM readable by most computer DVD drives? Thanks 92.15.16.146 (talk) 11:07, 19 February 2011 (UTC)
 * No, see DVD-RAM. 71.141.88.54 (talk) 13:51, 19 February 2011 (UTC)


 * I also have to caution you that even a DVD-RAM disc may not be readable after twenty years in a drawer. The question of backup media reliability over the long term is pretty much a FAQ here at RD/C and it'd be nice to have the backup article expanded to explicitly discuss the expected lifetime of the different common media used for backups.  Our article Digital preservation is sort of all over the place but it touches on a few related topics.  Comet Tuttle (talk) 00:56, 22 February 2011 (UTC)

Strange connectivity issue
When I use my router's ability to change its MAC address ('MAC address clone'), I lose my connection to the internet until I set it back to the old default address. However if I connect through a different router or even directly through my computer (all of which have different MACs), there doesn't seem to be a problem. WHy is this? 72.128.95.0 (talk) 20:15, 18 February 2011 (UTC)
 * I'm assuming you're using a cable internet provider? My guess is that the MAC address of your alternative router and your PC are also logged by your provider as legitimate addresses, but that the new address you change you router to isn't.--Phil Holmes (talk) 10:50, 19 February 2011 (UTC)
 * Have you tried unplugging the router and plugging it back in, with the new MAC settings? I've had issues with cable modems freaking out when the MAC address of the connected device changes but the link stays steady. Replugging the router or rebooting the cable modem might solve the issue... 151.151.16.7 (talk)

Long term data storage
Some what to do with the DVD question previously, If i took various kinds of data storage (CD's,DVD's, floppys, USB drive etc and any others ppl think off) put them in a box and left them at say standard room conditions. (So there not in perfect isolation but then there not being kicked around and left in the sun). Which would "hold on to" its contents for longer? ie if i came back in 10 years time and assuming i had kept the various drives/drivers etc, would any of them be expected to of had some of the data "disappear"?--86.145.90.102 (talk) 23:17, 18 February 2011 (UTC)
 * I beieve that if stored in room temperature in sealed cases I think the will work perfectly after ten years. Even more if you put it in a vacuum I would think. General Rommel (talk) 23:27, 18 February 2011 (UTC)


 * Have a look at the Library of Congress CD-R and DVD-R/RW longevity project, part of the Digital Media Preservation project. Disc coatings can peel and crack.  In this thorough report, Longevity of CD Media - Research at the Library of Congress, quantitative failure rates are published.  Nimur (talk) 23:34, 18 February 2011 (UTC)

Here's a similar question from the archives which has some interesting information 82.43.92.41 (talk) 00:01, 19 February 2011 (UTC)

For data that are actually high-value, you need not only media to store them on, but procedures for verifying them, copying them to new media, switching from older media to new ones (e.g. to maintain compatibility with new machines), and so on. Maintaining a long-term data archive will end up being not so much like keeping a bunch of books in a vault, but rather like running a scriptorium. --FOo (talk) 07:01, 19 February 2011 (UTC)