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Re: 2.6+ kernel make-tag problem

in reply to darkestkhan <darkestkhan@gmail.com>

Thank you very much for even showing concern about root=, uuid, newbies, lk README. I was commenting on [improvements] that may dis-courage newbies for lack of howto.

Sorry this is long but it is work I can't do again later. I spent a good hour searching google and manuals to see if the previous, that "hda==sda but use uuid isn't depreciated" is true.

FIRST UUID.  Then "far below" "./linux" (/usr/src) and kernel bugs org.

No sorry.  It's diffuclt to find.  I don't see where it's been documented except xyz (see below).

#1. Why would I search Debian / Ubantu Distro. to boot a Linux Kernel ?

#2. Not there anyhow,  Not really, see why below.  (Not unless your real lucky).

#3. You said "a notice was issued a few years ago". yes, and hardly. current docs still conflict and are worse since they now "assume" everybody uses uuid, thus emit no advice about no notice for those not using it.

#4. a while back I looked into uuid and decided no, I didn't like uuid for many reasons. maybe now I'd say yes: but really "that hda changed to sda" at boot time i might STILL NEED TO KNOW.

So YES I think it neesd to be in both debian guides but MORESO that it should be in lk's Documentation/ and even a menuconfig help warning.


As for kernel Documentation.  Even if I knew UUID was an issue I wouldn't be tipped off:

$ grep -ir "uuid" Documentation/
   linux/Documentation/debugging-via-ohci1394.txt ?
   laptops/thinkpad-acpi.txt ?
   NOTHING I should be interested in arises.

"4.8.2. How to recover from the problem after the upgrade"

The above DOES HAVE what you refered to, your right. HOWEVER it's hard to find and already outdated. Also the "new" material I'd see when upgrading removed that.

BUT. You'd be lucky to search for UUID and find that document !! And I didn't find it with a google search but a search on a Debian server. I found it ONLY because a) was lucky and b) already knew the answer I was looking to find.

First lenny's inst guide did say that. i upgraded from sarge to squeez, no time for lenny. only becuase firefox refused to upgrade if I didn't. maybe I need a web browser emulator!



Searching google for UUID I see: i would like to find out how to change my system so that it would use UUID/labels instead of the BUS locations (eg: /dev/sda1).

HOWEVER. I've never heard of UUID except as a disk label, how would I know to search the internet to pass UUID to kernel (which reads UUID after being told which disk)? And why would I?

PRECAUTION: I see one guy ask "how do I infer my uuid?" good question. what if you don't have it written down??

Also my sytem has both ide and scsi drivers in use. I have a "bad bios". I might need to kick the kernel to use the right driver for detecting the right hadware, "bios drive mapping issues" v "my drive's bios or boot bios is not 'correct'".

why would I google UUID if I'm looking for VFS can't mount, block (0,0) unkown error ? also I did search for the error given, I didn't see anyone had an answer and nothing about uuid associated or aliased either.


"Debian GNU/Linux Installation Guide"


I can't find it here. This guide assumes your doing as expected (in which case it uses UUID without asking). Must be in "reference" or "upgrade" manuals.

If i were installing on an existing drive i might be stuck. Infact this manual more assures me there wouldn't be a problem !

D.1. Linux Devices

In Linux various special files can be found under the directory /dev. These files are called device files and behave unlike ordinary files. The most common types of device files are for block devices and character devices. These files are an interface to the actual driver (part of the Linux kernel) which in turn accesses the hardware. Another, less common, type of device file is the named pipe. The most important device files are listed in the tables below.

fd0 	First Floppy Drive
fd1 	Second Floppy Drive

hda 	IDE Hard disk / CD-ROM on the first IDE port (Master)
hdb 	IDE Hard disk / CD-ROM on the first IDE port (Slave)
hdc 	IDE Hard disk / CD-ROM on the second IDE port (Master)
hdd 	IDE Hard disk / CD-ROM on the second IDE port (Slave)
hda1 	First partition of the first IDE hard disk
hdd15 	Fifteenth partition of the fourth IDE hard disk

sda 	SCSI Hard disk with lowest SCSI ID (e.g. 0)
sdb 	SCSI Hard disk with next higher SCSI ID (e.g. 1)
sdc 	SCSI Hard disk with next higher SCSI ID (e.g. 2)
sda1 	First partition of the first SCSI hard disk
sdd10 	Tenth partition of the fourth SCSI hard disk

C.4. Device Names in Linux

Linux disks and partition names may be different from other operating systems. You need to know the names that Linux uses when you create and mount partitions. Here's the basic naming scheme:


      The first floppy drive is named /dev/fd0.

      The second floppy drive is named /dev/fd1.

      The first SCSI disk (SCSI ID address-wise) is named /dev/sda.

      The second SCSI disk (address-wise) is named /dev/sdb, and so on.

      The first SCSI CD-ROM is named /dev/scd0, also known as /dev/sr0.

      The master disk on IDE primary controller is named /dev/hda.

      The slave disk on IDE primary controller is named /dev/hdb.

The master and slave disks of the secondary controller can be called /dev/hdc and /dev/hdd, respectively. Newer IDE controllers can actually have two channels, effectively acting like two controllers.


"Debian Reference" current...

9.3.3. Accessing partition using UUID
"mount(8) with "-U" option can mount a block device using UUID, instead of using its file name such as "/dev/sda3"" With that I assume whoever wrote it has a scsci disk. why wouldn't I?

3.3. Stage 2: the boot loader
"UUID (see Section 9.3.3, “Accessing partition using UUID”) may be used to identify a block special device instead of its file name such as "/dev/hda3"," Here it doesn't say not to use hda, rather it says "optionally you could use something else".

LASTLY. For "Debian Reference". If I see an arcane reference to "UUID" (not a unique label) that says I should turn my boot and fstab upside down on a whim: I'm unlikely to do it if it's "optional".

MORESO. It's NOT a bootloader or partition issue but a kernel parameter issue. It's VFS that needs this to know what hardware to check partitions IN, and needs it as a kernel parameter. The error message listed

Now that I know the "magic code UUID" I see some Ubantu references. Not Redhat, Slackware, Debian, Knopix, or what. For Ubantu it doesn't say "don't use hda that won't work anymore" it only suggests "how to use uuid".


www.gnu.org, grub 2 docs say:

"Unfortunately, even OS device names are not always stable. Modern versions of the Linux kernel may probe drives in a different order from boot to boot, and the prefix (/dev/hd* versus /dev/sd*) may change depending on the driver subsystem in use."

Once again this doesn't apply to me I'd think: since I've always had sda and hda in various machines and don't care to "fix it".

Also true is that GRUB's detection is only that, it does not tell kernel. You have to use kernel params separately and depending upon the kernel in use.

The issue is does linux kernel param change, of which hardware driver will be used (ide driver, scsi driver), without documentation.

After all. if I have 2 UUID similar it becomes important maybe which hardware to check. How? by specifying the device driver and using parameters ide hope. though i don't care - probably not happen to me, not this year, anyway.


While I really don't mind uuid or not: i'll do it. Just because it's a good idea for some doesn't mean I need it.

And I still think UUID is found on a disk label which is read AFTER a device driver hath been invoked. Thus it seems a falseness to use it that way somehow.

I'm not a gov. agency, i'm sticking with sda unless it NEEDS fixing, but for now it works fine.


Release Notes for Debian GNU/Linux 6.0 (squeeze), 32-bit PC

Chapter 4. Upgrades from Debian 5.0 (lenny)

again, I never used lenny so why would I read this ??

4.6.2. Device enumeration reordering

"In lenny and later, a new kernel mechanism for hardware discovery may change the order in which devices are discovered on your system on each boot, affecting the device names assigned to them. For example, if you have two network adapters that are associated with two different drivers, the devices eth0 and eth1 refer to may be swapped."

I stop reading there. eth0 or eth1 reordering is an old linux issue I've already read howto on and dealt with many a time.

NOTE: numbering and device driver are wholely not the same subject.

"... /dev/disk/by-uuid/ directory or LVM device names in /dev/mapper/." (btw I often have not compiled it into my kernel: i like /dev the way it is (or was) for a few reasons.) (for example, I still have old floppies that don't use dynamic /dev, and things like devmapper increase kernel size)

"[10] Some devices, such as those used by crypt, RAID or LVM have stable non-UUID identifiers. In these cases you should use the name of the devices, which are already unambiguous and stable."

so now I wanna use UUID ?  I know microsoft or IBM probably uses it a whole different way so ??

5.1.1. Migration of disk drivers from IDE to PATA subsystem

The new Linux kernel version provides different drivers for some PATA (IDE) controllers. The names of some hard disk, CD-ROM, and tape devices may change.

It is now recommended to identify disk devices in configuration files by label or UUID (unique identifier) rather than by device name, which will work with both old and new kernel versions. Upon upgrading to the squeeze version of the Debian kernel packages, the linux-base package will offer to do this conversion for you in the config files for most of the filesystem-related packages on the system, including the various bootloaders included in Debian. If you choose not to update the system configuration automatically, or if you are not using the Debian kernel packages, you must update device IDs yourself before the next system reboot to ensure the system remains bootable.


Back to the beginning.  I found the "answer" I've used linux since early '90's.

My original point was: wouldn't that suck if you were a newbie ? Especially when most docs still conflict?

And who will update this excellent newbie document, circa 2002 though ??


Really I care not if I'm "upgraded uuid" or not. Useless to me. It's the nuisance or time I'm concerned of, and moreso the impact for someone who didn't know "all that" in the first.

Thank you very very much for even showing concern on the topik, flames or not,

	John Hendrickson

far below,

What is ./linux you asked? I personally use /usr/src and unpack the kernel tarball. /usr/src/linux-2.6.38 and etc. This is obvious to us both but:

$ cd /usr/src
$ if ! wget http://ftp.kernel.org/pub/linux/kernel/$V/linux-${VERSION}.tar.g
$ tar -xzf linux-${VERSION}.tar.gz

The NEW readme doesn't say "make modules". However. If I do "make" then "make modules install" it gets the error. (if i start dep, clean, mrpoper or not) If I use OLD readme "make" "make modules" "make modules_install" it's fine. maybe it's specific to 2.6.38 I don't know.

Kernel bug reports should be avail. ipv4? Who knows. They weren't the day I tried. I haven't checked again, yet.

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