Category Archives: Computers

Posts on computer science and the web, rants about OS:es, Window Managers, and the like.

Computers

Mounting devices with UUID identifiers instead of using /dev paths

I don’t know why, but from time to time drivers are assigned other “/dev”-paths on my ubuntu 6.10 LTS GNU/Linux server. I think a removable USB driver might have something to do with it…

However, when that happens it is a complete pain in the a$$ because if the driver is relocated, the system cannot find it and if it is mentioned in /etc/fstab the system reasons (justly so, I might add) that if it can’t find the drive it should pull the emergency break and jump into a rescue prompt (where mostly everything is disabled), letting the user (that’s me) deal with the problem.

I usually press the CTRL-D command exiting the shell and getting back to the boot process praying that no vital driver was lost. (I’m not really a guru, just a poor guy trying to make live a little easier).

For some reason (touch wood!) the drives with the boot image or with system specific things on them has never been moved around this way. Usually its the USB drive itself (when I still had it in the fstab) that has moved (I’ll get back on how to make it auto-mount in a later post) or in this latest case, one of the back-up drives.

However, there’s a solution. If you run GNU/Linux you might have seen it in your fstab-file. The use of a UUID to do mount instead of the regular /dev/something. My desktop computer’s fstab looks like this:

# /etc/fstab: static file system information.
#
# <file system> <mount point>   <type>  <options> <dump>  <pass>
proc            /proc           proc    defaults  0       0
# /dev/sda1
UUID=e1f37856-6cfd-43f9-bea0-d4c2e43afe29 /     reiserfs notail,relatime 0  1
# /dev/sda6
UUID=64549135-a478-4aef-bb2a-da37d245dd9c /home reiserfs relatime        0  2

From this rather confusing array of characters (I had to shrink the spaces in order to fit it on the site) you can determine that there’s three devices mounted at start up (proc, sda1 and sda6, I’ve got even more, but the exact number of devices are not interesting for this discussion).

The proc device always resides at the file system “proc”, and it does not have nor need a UUID. However the sda1 and sda6 devices are regular hard drives (formatted with reiserfs) and they can change designation, for instance if I start rearranging my sata-cables or start a USB drive in a USB slot with a lower ID than those of my sda drivers (I’m guessing on that one but I’ve seen it on my server so…) These are therefore interesting to mount not by their dev-names but by their UUID’s. The UUID are stored on the drive itself and it wont change unless the drive is reformatted. The drive can be moved, turned off, turned on, it will still have the same UUID.

So, using UUIDs are a good idea when I want to create my new, drives-moving-around-proofed server configuration. The first step is to determine what UUID the drives have. This is done with the following command:

sudo vol_id -u /dev/something

I had problems finding “vol_id”. It was not in the PATH, and could therefore not be run like above. I did a locate (locate vol_id) and found it in “/lib/udev” so I prepended that path to my command. I’ve also to determine how to get the UUID from a swap partition, but for now I’m happy to have the infringing drives on UUID and hope the swap wont move (perhaps with the extra 2GB of memory I also stashed in it will need the swap even less, but anyway)…

You won’t be able to determine the UUID of any drive part of a software raid configuration (but then again, the software raid is able to do its own magic locating of drives regardless of their sd-number — trust me, I’ve done that as well — so they won’t need a UUID anyway — wouldn’t surprise me if raid uses the same scheme behind the scene though)

Let’s look at the changes I did in my fstab file (always make backups before you start messing with this file! If you fail to set it up correctly your system will probably not start at all so have a live-cd handy before trying to do this!):

/etc/fstab before I changed it (just a part of it)

# /etc/fstab: static file system information.
#
# <file system> <mount point>    <type>   <options>           <dump>  <pass>
proc            /proc            proc     defaults            0       0
/dev/sdc1       /                reiserfs notail,user_xattr   0       1
/dev/sdc5       /home            reiserfs defaults,user_xattr 0       2

As you can see the situation is not as clear on this machine as it was on my desktop machine. Here sdc is the main system drive and that alone is a, well not a worrisome problem, but a slight discomfort… sdc never moved around, but being that I have a bunch (8 or 9) sata-cables in a large but far-from-large-enough case I’m bound to switch them around one day or another…

Anyway, using the above vol_id command to get the UUIDs of the drives, I’ve updated my fstab to look like this (still only partial fstab but you get the idea):

# /etc/fstab: static file system information.
#
# <file system> <mount point>    <type>   <options>           <dump>  <pass>
proc            /proc            proc     defaults            0       0
#/dev/sdc1
UUID=716cf691-dabd-4894-8e46-bc02b4c092b4 /     reiserfs notail,user_xattr   0  1
#/dev/sdc5
UUID=9587a32e-ebb2-45ab-9e68-7a66cf43d6b4 /home reiserfs defaults,user_xattr 0  2

Unfortunately I have the same problem as above, the lines wont fit in the editor (or on the site) if I tabulate them correctly, but hopefully you’ll still be able to connect the dots. Every group of white spaces (space, or tab) in the file counts as a field separator. I’ve commented out the “/dev/sdc…” section, added a line feed and replaced it with the “UUID=…” section, and then left the rest of the line intact.

This makes sense since I’ve replaced one identifier (“dev/sdc…”) with another (“UUID=…”). So, after the original “dev”-version of the file has been safely backed up, the entries in the original “/etc/fstab” has been checked and double checked, it’s time to restart and pray this will actually work. :O

Here’s a few links you might want to check out before you give it a try:

Good luck!

Update: If, however, you’re using LVM, you’ll get stable device names and you should mount these instead. If you use LVM-snapshots you’re going to get two or more volumes with the same UUID, and in that case you should absolutely not use UUID mounting.

Computers

Electornic Art’s Spore sued because of its DRM

Electronic Art’s game Spore was on September 22nd hit by a class action lawsuit because of its DRM (Digital Restrictions/Rights Management). Or actually the fact that the DRM was secretly installed and made uninstallable.

However, I am fairly certain the lawsuit wont fly. EA told those buyers there was a DRM involved, and they have since then provided an uninstaller for the DRM.

I think we, consumers, should stop buying games with DRMs, and instead protest against the use of DRMs. If we don’t we’ll end up in a world where every software we run are for hire and nothing, not even the contents of our own harddrives, are our property. That would be a bit like hosting a virus or a parasite… unwanted, unpleasant and uncalled for.

Here’s some other reports:

http://hothardware.com/News/Spores-DRM–ClassAction-Lawsuit-for-EA/

http://www.techradar.com/news/gaming/ea-faces-class-action-lawsuit-over-spore-drm-470850

http://www.1up.com/do/newsStory?cId=3170131

http://www.crunchgear.com/2008/09/25/ea-facing-class-action-lawsuit-over-spore-drm/

Computers

Disassociating .EXE-files

Windows doesn´t work as it used to after I associated the .exe-extension to putty.exe...
Windows doesn´t work as it used to after I associated the .exe-extension to putty.exe…

I am clumsy. I can only confess. But I still think what I did should not be possible to do. I mean, it’s not like having a foundation is optional when building a house… why should running exe-files as executables be an option?

Okay, this is what I did: I have an exe-file (putty.exe) sitting on my windows start-menu (oh did I forgot to mention this was a problem in Windows? Sorry…) However, I happened to move the folder where this file was located. Not so good perhaps because now, of course, the link to putty fails.

So, I right clicked it and selected properties, trying to figure out if there was a way to redirect the link. There was… kind of… there was the “Open With” button. I thought, hey, that could be it, let’s try it and see what happens. So I clicked it, opened it and selected putty.exe. It didn’t work.

Or, well. Windows did what it thought I wanted it to do. The dialog I’ve quickly scanned before selecting a file was the dialog for reassociating the .exe extension … with putty.exe. This, however, was not in Windows liking, so now whenever I click an exe I get the dialog here to the left.

It would have been really bad if I hadn’t done one good thing that day. I installed cygwin… and weehoo… windows programs can be started from cygwin. Phew! I can tell IT-support the problem is solved… almost!

At least one good thing. The problem is rather easily solved. Let’s see if I can remember the steps the rather stressed out support technician went through. Open “My Computer”, select “View” in the the menu and go to associations in the dialog. What we want to do is associate the “Application” association (There are a number of other “Application”-associations but we never touched them… and if they haven’t been changed, don’t touch them, and if they have, I’ve no clue what extension they should have so … don’t touch them…)

Since this is a “built-in” association it won’t be in the list of associations, we have to create it again (?!). Click “New” and in the new dialog enter “EXE” as the extension and from the drop down select “Application”. Don’t push any buttons! Without having to push any buttons, but with the kind mercy of the Gods of Windows, a message that the “EXE association has been changed” will appear along with a button to reset it to the default settings. Push the “reset”-button.

And this good folks is how my problem was solved. I came a cross a few “regedit-hacks” but I wouldn’t recommend them unless this solution doesn’t work. Also, make sure to reboot after you’ve reset the association because for me assorted things like remote desktop links and some such started to get broken after a while. (Don’t ask. I have no clue why!)

Good luck and don’t experiment with your computer, naughty! You can break something for real…

Computers

Naivized by Linux

I’m all for Linux. Really. I love it, even though it’s from time to time a hate-love. However, I just realized one thing Linux has done to me that isn’t so good when you are forced to work and live in Windowsland.

I’ve become totally naive when it comes to certain aspects of the Windows world.

A couple of weeks ago I was looking for a program to help me keep my local hard drive synchronized (or in fact, backed up) to the network drive. A few factors have made this an issue for me, bad network performance but also the ability to just pick up your laptop and not worry about network connection to mention a few.

Anyway, I browsed around, moderately annoyed trying to avoid all the $oftware in favor for something simple that could do the job but wouldn’t cost money… just like home in Linuxland, right?

So I came a cross one really promising piece of software (no need to mention which since they’re not lone sinners :o), downloaded, tried it out and thought… hey this works! It had good integration with the desktop and a clean and simple UI and simple yet powerful features.

Great. Then today I spoke with a colleague who had been on the same mission and told him this was good software. He was rather surprised, since he had long ago figured out the software was not at all free (even though it’s listed as free software on several places, and they say it is free). The surprise will come after 30 days when the software stops working, for all intents and purposes unless you pay them money.

There’s nothing bad with companies asking for money. After all, I ask for money for working for a company, so the company should ask for money for selling my work, right? However, the serious problem is the lying part of the deal, where software companies say they are delivering free software where in fact they aren’t. In my case it ended up wasting several hours setting up the sync for real and would have wasted even more time had I been caught unaware when the 30 day trial was up. This, the lying seems, to me, to be a direct symptom of the software development model used…

There are no such thing as a free lunch, not even in the Linux world, but there you pay with time, and your apps aren’t programmed to stop work after 30 days. They might, because you’ve downloaded beta software, but that’s because some one did not program, or program right, not because someone did.

Anyway, I was baffled, totally unprepared and realized Linux naivized me! Wooh!

Computers

Hacking Windows Remote Connection (MSTSC.EXE)

WARNING: The below tip will kick out one of the already logged in users. This behavior may have been added after I came up with this advice, or I’ve always been the evil person on the block 😀

Ever been turned down by a Windows machine over Remote Desktop because it already had too many connections?

Even though there are no way to connect using the standard remote desktop program you can still “hack” a connection. Sure the limitation exists, probably to sell more licenses or to protect the host server from getting too many connections, but to get past it you do the following:

mstsc /v:myhost.com /F /console

Where myhost.com is the name or ipnumber of the server you are trying to remote to. /F means a full screen connection, /console means to connect to the “console session of the server” (whatever that means, it anyhow results in you getting in although the server would otherwise refuse you).

The full format of the MSTSC command call are:

MSTSC [<Connection File>] [/v:<server[:port]>] [/console] [/f[ullscreen]]
[/w:<width> /h:<height>]

<Connection File> refers to an rdp file to be used with the connection (good if you need to make local drivers or other resources available or set up the connection otherwise).

You can also call MSTSC with the “/edit” switch if you wish to edit a connection file:

MSTSC /edit <Connection File>

Finally you may also migrate files by using the “/migrate” switch (not 100% sure how this is done though since I don’t have an older version file to test with).

Computers

Office 2007: Microsoft shoots itself in the foot?

I have the somewhat dubious pleasure of working at a place where the migration from Office 2003 to 2007 is halfway done. Now, usually this should be no problem, but a couple of factors have cooperated to make it one.

Office 2007 uses a new (and improved?) format (they added an x to all their file name extensions, read more about them here). This could be all good and well if it had not been for the fact that new versions of Office now uses these formats per default. Okay, a user a bit savvy might sooner or later notice the “x” at the end of all filenames… but only the users that have disabled the setting in Windows to hide these formats…

This leaves us with senders, running Office 2007, unable to tell if they saved the file in docx or doc format, and the recipients with Office 2003, unable to read these files. Even though there is an update, a lot of users aren’t comfortable with doing that… heck, I’m scared of doing unneccessary stuff to my wobbly M$ installation!

The end result becomes pretty predictable: chaos, disillusioned users, and … a great day to start talking about OpenOffice.org? (even though it does not yet support the Office 2007 format).

Computers, Science and Society

Open source v.s. Closed source

Working with closed source products (Microsoft Visual Studio, .NET, ASP.NET, SQL server, and Oracle) while at the same time experimenting with open source products (Eclipse, Java, MySql, and Spring) I am constantly baffled by the persistance of closed source developers and business people in their handling of second grade support, bad information, and lacking products.

Continue reading Open source v.s. Closed source →

Computers

Badblocks

It took me some time to find out the equivalent of Window’s checkdisk/scandisk/chkdisk on Linux, but trust me, there are several.

For starters I am going to take a look at badblocks, a command that as the name implies, looks for bad blocks.

The basic format of badblocks are:

badblocks [options] device

If you have a fresh drive with no data or data that can be deleted on it you can do:

badblocks -s -w /dev/sdb

Note however, the -w command will erase all existing data on the drive so do not use it for drives with existing file systems on them. You cannot use -w on a mounted drive, unmount it first. The -s flag makes the command show a progress bar. This could come in handy when you are testing larger drives since even the fastest systems will take at least an hour to test an average sized drive (my 400GB took about 2 hours on a SATAII system).

If you want to test the drive without deleting data you can use the -n switch which will use non-destructive write-read mode, however, this switch can, for obvious reasons, not be combined with the -w switch.

badblocks -s -n /dev/sdb

Links:

Computers, Humor

DoNothing and numerical dyslexia

Small beauties in programming… and not all of them are made up either ;o)

DoNothing:

function DoNothing() {
Nothing();
}

Find one error:

private static final int TWENTYFOUR = 24;
private static final int THIRTYEIGHT = 32;
private static final int FOURTYTWO = 42;

Computers

The mystery of the magic file (or how i invented the .rte and .rtg file formats)

I’m just back from a head spinning experience of extreme Windowsism.  A file that refused to be renamed, or deleted… until ten minutes later…

What happened was that I wanted to rename a file.  Like I usually do, I clicked the file, then pressed F2, got the “editable” view of the file name and started typing.

Nothing happened.

I clicked around, trying to see if the computer was just slow or something like that.  Well… the file explorer did not respond at all…

It was frozen.  So I waited for it to unfreeze.  Which it didn’t.  It apparently had crashed.

I force-quitted.  Restarted and retried.  After all, perhaps it was just a fluke?  Right?

Nope.  Same exact problem.

I scratched my head, thought for a bit and rejected a number of alternative ways to go.  I guessed it was time for the daily reboot… again today.  And rebooted the system.

Once back in the catalogue (five minutes later) I found the same problem persisted.  No rename, no file explorer, nothing but kill the program.

I was able to “solve” the problem however, by copying the file.  Once I had it was in fact possible to rename the copy.  All I had to do now was to remove the old file and, although kind of axy (as in trying to carve an inch high wooden statuette with an axe), the problem would be solved.

The file did not want to be deleted.  However, the file explorer did not freeze this time so chalk one up for windows?  Or not.  Shutting down the file explorer and restarting it did not help either.  It was time to harvest the vast experience of the firm.

I asked around in the office landscape trying to find someone that could help, and I got a number of helpful advice like “have you restarted the file explorer?” or “have you rebooted the machine?”  All of which was rather not what I hadn’t already tried.

Finally someone suggested: “put two files in the same folder where the problematic file is placed, name them so they appear just above and just below the file with the problem, put something like ‘erase me’ at the end of them, wait a week and delete the file then.”

After having hyperventilated for a while to get the whole concept into my head and make it stick long enough to do what the guy had suggested I went ahead.

My magic file was named something like “My document 2.rtf” so after some experimenting with names that would place the file exactly where I wanted them I came up with:

My document 2.rte.delete.me.txt
My document 2.rtf
My document 2.rtg.delete.me.txt

Now for the mind blowing finale.

Once I had the files in place my folder looked like:

My document 2.rte.delete.me.txt
My document 2.rtg.delete.me.txt

The magic file had disappeared!  Finally deleted!!  Only about ten minutes after the button was pressed!!!

That was when I noticed the dialogue boxes saying “The file cannot be renamed, it has disappeared.”  They were, in true windows style hidden under the file explorer window…

Aha, was my first thought, problem solved…  Then I felt a chill going down my spine.  Didn’t I try to rename before I deleted?  Or did I try to delete first and rename later?

No! my mind screamed.  I had a file, whose content was important but whose name was wrong.  So deleting before renaming would be stupid.  And renaming after I’d copied the file and renamed the copy would be equally stupid (not to mention impossible… there was already a file with that name…)

Somehow windows had confused the order of the operations?!  BRRRRR!!!

You might think, hey he was working with a networked drive and the net was having some kind of problem or the order of the packages got confused.  It’s a good idea, it could really happen, even though I think the Samba protocol (or whatever windows have chosen to call it) should be able to handle packages coming in haphazardly without getting confused like this, and the most probable result of Samba not managing that should be some kind of failure, even total failure demanding the drive to be remounted (or a blue screen or whatever XP uses when the OS-programmers run out of money, time or happiness).

Enough about networked drives… the drive in question was local!  No network, no delays, not even cables (USB/FIREWIRE/eSATA or what have you)… unless you count the system bus.  Does windows use TCP/IP on the system bus?

Well… thank God I have my important files on another OS altogether!  Not to mention on RAID and USB backup…

Computers are scary… Windows computers are terrifying!