What is the correct fsck syntax for issue with invisible disk ?

Question

Hello everybody,
My problem actually (I also have a problem with the 17" Install DVD) is to repair *3 disks* with *fsck command*, as the filesystems are damaged. I phoned Apple Assistance Saturday, for about 30 minutes, but finally the Advisor sent me a link to one of their thousands (and sometimes obsolete) articles, and the solution wasn't there entirely.
I'll describe you the problem :
One of my USB external disks (4TB data) *doesn't appear* after Startup, but when I use the Install DVD and Disk Utility, the application tells me it's OK, that the disk "SEEMS" to be alright etc. That's false.
When I reboot with *Cmd + S* (root level), and tell Terminal (I have been obliged to print the four states of an American Extended keyboard) :
"sudo fsck -fy /dev/disk4s1"
the reply is :
"BAD SUPER BLOCK: MAGIC NUMBER WRONG
LOOK FOR ALTERNATE SUPERBLOCKS? yes
SEARCH FOR ALTERNATE SUPER-BLOCK FAILED. YOU MUST USE THE
-b OPTION TO FSCK TO SPECIFY THE LOCATION OF AN ALTERNATE
SUPER-BLOCK TO SUPPLY NEEDED INFORMATION; SEE fsck(8)."
So, I use the *-b option* of *fsck command*, and :
"fsck: -b flag *requires a number*"
"-b size Specify the size, in bytes, of the physical blocks used by
the -B option."
So, I'm searching *since 3 days* (and *I'm learning a lot*, but nothing, of course, concerning my problem) the full info command to know *what sector address* I have to tell to -b to install an alternate superblock, because I need to know exactly at which places filesystems and *data start* and end.
You understand, I suppose, that I can't use any of my softwares, because the disk is INVISIBLE (doesn't exist) after normal restarting.
It's not MOUNTED nor UNMOUNTED.
It exists (very well, thank you) when rebooting *with Apple Install DVD*.
I'm under *Snow Leopard 10.6.5*, and I don't know if, perhaps,
*there wouldn't be a problem* (or more) with this update ...
That's what I've seen, in any case, on other places here,
about several different issues.
Please, Bob, Gary, Camelot, etresoft, Bill, Jun, Nils, Cole, Charles, Michael,
gimme some help !
If someone has the full solution, a beginning of solution,
or a path to solution,
thank you very, very much in advance !
With my best regards
Vialatte

Answer 1

Dear Camelot,
First, thank you very much for answering me and try to help me ;
Secundo, please read, if you have time, what I replied to Bill Scott,
and I have to thank you also for your slightly better contribution and understanding.
Some words of what I've replied to him are written for you too :
"I type *sudo fsck -fy /dev/disk4s2* (not s1, of course, and *Camelot is perfectly right*, having remarked this mistake, as *s1 is dedicated to partition map* volumes).
There's also *a strange thing* with Disk Utility when starting from DVD :
it doesn't display the s1 volumes as usual."
As you've read it in my reply to Bill, it's a *complicated issue* and *Apple has no response*.
You tell me : "+Good luck with that.+" It starts badly.
"+It's been a long time since I've had to deal with superblocks+"
I totally ignored their existence …
"+- they just don't come up any more,+" What is the meaning of this sentence ?
"+but I don't know any way of recovering the superblock address after a disk has failed.+" That's the matter of my question : *Is it a failure ?*
"+Typically (at least, historically) you get the superblock addresses in advance, storing them somewhere safe until you need them.+"
That's a total discovery for me.
You tell me then : "+Are you talking about in the Finder here?+" Yes and no, I talk about the Sidebar (see below), but it's part of the Finder.
"+Have you checked the Finder's preferences to make sure it's just not hiding external drives?+" I did, when you told me to do so.
"+Since everything else tells you that the drive is OK+" Yes, you're right, when starting from Install DVD, that's *very strange*, but remember fsck doesn't say *the same at all* as Disk Utility ... "+this just sounds like a Finder preference setting to me.+"
I'm sorry, it would have been wonderful. My settings are correct, that means :
NOTHING on Desktop, ALL (including Computer) in the Sidebar (and clicking on Computer allows me to check that *no volume* has vanished from Sidebar (it happens sometimes).
"+If it's not the Finder prefs, then please post the output of diskutil list in order to troubleshoot further.+"
Here it is (a little far below), but there's *none of the 2 4TB volumes* (yes, there are two disks missing now) here, because, as I already said that, they are invisible for the Finder and *Disk Utility*, and I think *it's the same for Terminal.*
You'll note there's *no BOOTCAMP partition* here (I removed it temporarly to solve this issue), and don't be afraid if there are several systems on the internal HD.
As I noticed it here and there, there are problems with 10.6.5.
So, I try to work with 10.6.4 (delivered with MBP 17"), but have also an universal 10.6.0 Snow Leopard, with which I can configurate 10.6 *at any state*.
Unfortunately, I *can't use* (it so that Apple decided to do) the DVD delivered with my 15" MBP (rejected by 17"), because it is with my MBP 15" that I formatted those disks.
*Another thing :* If I didn't want my wife *to install herself* (with me to help her) the 15" MBP I've gave to her (there's the 17" new 500GB 5400rpm installed in it by me), I would already have tried to connect these two 4TB, just to see.
Last login: Fri Nov 26 21:22:38 on ttys005
sys171064:~ OH$ diskutil list
/dev/disk0
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *500.1 GB disk0
1: EFI 209.7 MB disk0s1
2: Apple_HFS Seagate 149.9 GB disk0s2
3: Apple_HFS System 17 64.9 GB disk0s3
4: Apple_HFS Sys171064 34.9 GB disk0s4
5: Apple_HFS For Alu Black System 149.6 GB disk0s5
6: Apple_HFS SL 10.6.x 100.0 GB disk0s6
/dev/disk1
#: TYPE NAME SIZE IDENTIFIER
0: Applepartitionscheme *16.1 GB disk1
1: Applepartitionmap 32.3 KB disk1s1
2: Apple_HFSX olivier_herrbach 16.1 GB disk1s2
/dev/disk2
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *1.0 TB disk2
1: EFI 209.7 MB disk2s1
2: Apple_HFS HSD 01 TM 600 Go 599.9 GB disk2s2
3: Apple_HFS HSD 01 400 Go 120.6 GB disk2s3
4: Apple_HFS DiskTools > Seagate ... 279.1 GB disk2s4
/dev/disk3
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *1.5 TB disk3
1: EFI 209.7 MB disk3s1
2: Apple_HFS HELP ÉNERGIE 1,5 To 1.5 TB disk3s2
/dev/disk4
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *1.0 TB disk4
1: EFI 209.7 MB disk4s1
2: Apple_HFS HSD USB 03 1To 999.9 GB disk4s2
/dev/disk5
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *32.0 GB disk5
1: EFI 209.7 MB disk5s1
2: Apple_HFS Patriot USB Key 32 Go 31.7 GB disk5s2
/dev/disk6
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *1.5 TB disk6
1: EFI 209.7 MB disk6s1
2: Apple_HFS WD USB 1,5 To 1.1 TB disk6s2
3: Apple_HFS WD 02 350 Go Seagate 349.9 GB disk6s3
/dev/disk7
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *1.0 TB disk7
1: EFI 209.7 MB disk7s1
2: Apple_HFS HSD USB 02 50 Go 49.9 GB disk7s2
3: Apple_HFS HSD USB 02 715 Go 714.6 GB disk7s3
4: Apple_HFS HSD USB 02 110 Go 110.0 GB disk7s4
5: Apple_HFS HSD USB 02 100 Go 99.9 GB disk7s5
/dev/disk8
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *2.0 TB disk8
1: EFI 209.7 MB disk8s1
2: Apple_HFS WD USB 2To 2.0 TB disk8s2
/dev/disk9
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *2.0 TB disk9
1: EFI 209.7 MB disk9s1
2: Apple_HFS FW 03 TM 2To 2.0 TB disk9s2
/dev/disk10
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *1.5 TB disk10
1: EFI 209.7 MB disk10s1
2: Apple_HFS FW 02 1,2 To 1.2 TB disk10s2
3: Apple_HFS FW 02 200 Go 199.9 GB disk10s3
4: Apple_HFS FW 02 CS5MC 50 Go 49.9 GB disk10s4
5: Apple_HFS FW 02 Leopard 50 Go 50.0 GB disk10s5
/dev/disk11
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *2.0 TB disk11
1: EFI 209.7 MB disk11s1
2: Apple_HFS FC 02 Time Machine 1.0 TB disk11s2
3: Apple_HFS FC 02 SL 1To 999.5 GB disk11s3
/dev/disk12
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *2.0 TB disk12
1: EFI 209.7 MB disk12s1
2: Apple_HFS FC 01A USB 1To 700.0 GB disk12s2
3: Apple_HFS FC 01C 300 Go Leo 299.9 GB disk12s3
4: Apple_HFS FC 01B USB 1To 699.8 GB disk12s4
5: Apple_HFS Leopard 125 Go 300.0 GB disk12s5
/dev/disk13
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *2.0 TB disk13
1: EFI 209.7 MB disk13s1
2: Apple_HFS FW 04 TM 2To 2.0 TB disk13s2
3: Apple_HFS eDrive 12.9 GB disk13s3
/dev/disk14
#: TYPE NAME SIZE IDENTIFIER
0: GUIDpartitionscheme *2.0 TB disk14
1: EFI 209.7 MB disk14s1
2: Apple_HFS FW 05 2To 2.0 TB disk14s2
sys171064:~ OH$
As you and I see, I strongly believe that disk15s2 and disk16s2 (with s3, s4, s5 etc. partitions) are missing.
I must find a way to prove what I say to you. Remember that we are not in the case where I use *Cmd + s* after rebooting with Install DVD, but under normal utilisation. What follows has no interest :
Last login: Fri Nov 26 21:23:55 on ttys006
sys171064:~ OH$ sudo fsck -fy /dev/disk15s2
Password:
/dev/disk15s2: No such file or directory
Can't stat /dev/disk15s2
Can't stat /dev/disk15s2: No such file or directory
sys171064:~ OH$
So, I will now restart my MacBook Pro with Mac OS X 10.6.4 Install DVD, and go :
—1 in *Disk Utility* ;
—2 in Terminal (with *Cmd + s*).
I'll *note all* what I see, and then write you what I found.
You'll be nice to tell me if there's a way, in these conditions,
a) to *save Disk Utility log* ; or/and
b) to *save Terminal Output(s)* (.txt) ; or/and
c) to *take and save screenshots*, ; or/and
d) to *print anything*. (?)
as I don't know how it's possible to save these informations.
Thank you once more for your help. I'll do things now, but as it is 23:02 here in France, maybe I won't write you till tomorrow.
But, if you can answer to a), b), c) or d) above, post it to me please, because I'll go back here tonight.
And, also, *but I don't want to bore you*, I'd like to learn how to *copy and paste parts of messages* as you did, and how to *insert a Grab item (.png)* in a discussion, because an image is better than thousand words (that's what we say in France, but I'm sure we are not alone on Earth — like in the Universe).
With my best regards
Vialatte