Mounting Linux partition

Am Mittwoch, 28. Oktober 2009 20:11, VWWall a écrit :

> Strangely enough, openSUSE already has /dev/disk/by-label,
> which shows *all* partitions that have been given labels.

Actually, only file system labels are in /dev/disk/by-label,
not the partition labels assigned upon creation with
parted. Partitions used as swap or raid member do
not show.

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Marcel Bruinsma wrote:
> Am Mittwoch, 28. Oktober 2009 20:11, VWWall a écrit :
>
>> Strangely enough, openSUSE already has /dev/disk/by-label,
>> which shows *all* partitions that have been given labels.
>
> Actually, only file system labels are in /dev/disk/by-label,
> not the partition labels assigned upon creation with
> parted. Partitions used as swap or raid member do
> not show.
>
Those assigned partition numbers are shown at the end of entries in
/dev/disk/by-id and also in /dev/disk/by-path.

I used /sbin/e2label to label partition sda11 as "PCLOS_root".
It shows in /dev/disk/by-label as such.

I assume it defines, (and shows), labels actually written to the boot
record of the partition. These will show with blkid, as will the UUID.

--
Virg Wall

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David Bolt wrote:
>> And using df to add the name of the directory if available as well as
>> the free space. Simple.
>
> You already did something like that a short(ish) while ago. That script
> showed the free space available on the various mounted file systems,
> along with the total.

The remark was that df only showed the mounted partitions and also
unmounted partitions should be known. So there is a difference in need.

houghi
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of wallowing in the troubles of five billion strangers. -- Heinlein

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Shmuel Metz wrote:
>>What I do when I am done with YaST is edit fstab so that the order is in
>>an order I like. It will change lines, not delete them and add at the end
>>afterwards.
>
> I don't recall the details, but I've had cases where I edited a
> configuration file manually and Yast later overwrote my changes. I've
> found it to be safer to just use Yast across the board, and only edit
> those files that Yast doesn't handle.

I have heard about this by people over time, yet I never have noticed it
in the years since at least SuSE 6.3 where I have been using YaST and
edited fstab by hand.

Sure it changes my settings but only those changes that I select to be
changed.

I am not saying it does not happen. I am saying that apparently either I
am very lucky, I do not notice the changes or YaST is afraid of me and
does not dare to change things that I do not want to change.

houghi
--
Remind me to write an article on the compulsive reading of news. The
theme will be that most neuroses can be traced to the unhealthy habit
of wallowing in the troubles of five billion strangers. -- Heinlein

On Thursday 29 Oct 2009 02:42, while playing with a tin of spray paint,
Marcel Bruinsma painted this mural:

> Am Mittwoch, 28. Oktober 2009 20:11, VWWall a écrit :
>
>> Strangely enough, openSUSE already has /dev/disk/by-label,
>> which shows *all* partitions that have been given labels.
>
> Actually, only file system labels are in /dev/disk/by-label,
> not the partition labels assigned upon creation with
> parted. Partitions used as swap

Yes they do:

davjam@moray:/usr/src/packages/SOURCES> ls -l /dev/disk/by-label
total 0
lrwxrwxrwx 1 root root 10 2009-10-24 21:46 500_boot -> ../../sdc1
lrwxrwxrwx 1 root root 10 2009-10-24 21:46 500_root -> ../../sdc5
lrwxrwxrwx 1 root root 10 2009-10-24 21:46 500_swap -> ../../sdc2
lrwxrwxrwx 1 root root 10 2009-10-24 21:46 drive-f -> ../../sda1
lrwxrwxrwx 1 root root 10 2009-10-24 21:46 DVD_temp -> ../../sdb5
lrwxrwxrwx 1 root root 10 2009-10-24 21:46 ISOs -> ../../sdb7
lrwxrwxrwx 1 root root 10 2009-10-24 21:46 music -> ../../sdb6
lrwxrwxrwx 1 root root 10 2009-10-24 21:46 photos -> ../../sdb1
davjam@moray:/usr/src/packages/SOURCES> file -s /dev/disk/by-label/500_swap
/dev/disk/by-label/500_swap: symbolic link to `../../sdc2'
davjam@moray:/usr/src/packages/SOURCES> file -s /dev/sdc2
/dev/sdc2: Linux/i386 swap file (new style) 1 (4K pages) size 1116516 pages Label 500_swap

And swapon and swapoff can use the label to enable or disable the swap
partitions[0] in just the same way as mount and umount works with other
file systems.

> or raid member do
> not show.

Don't know about that as I don't use a raid array.


[0] My swap partitions are enabled in this way, just like I use labels
to mount the other (non-LVM) file systems.

Regards,
David Bolt

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On Thursday 29 Oct 2009 05:51, while playing with a tin of spray paint,
VWWall painted this mural:

> Marcel Bruinsma wrote:

>> Actually, only file system labels are in /dev/disk/by-label,
>> not the partition labels assigned upon creation with
>> parted.

Oh, I missed that part. Partitions don't have labels although they do
have types, e.g. 82 is for swap, 83 for a Linux file system, 8E for one
that's able to be a part of a logical volume.

> I assume it defines, (and shows), labels actually written to the boot
> record of the partition. These will show with blkid, as will the UUID.

The labels are stored inside the superblock of the file system, which
may or may not be the boot record (sector 0), and are of a variety of
lengths. Reiserfs and ext2/3 can have upto 16 character labels, and
will truncate a label any longer when creating the file system. XFS can
have upto 12 characters but will abort when creating a file system if
the given label is longer. JFS supports labels, but the maximum number
of characters for the label isn't specified in the man page.


Regards,
David Bolt

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On Thursday 29 Oct 2009 07:27, while playing with a tin of spray paint,
houghi painted this mural:

> Shmuel Metz wrote:

>> I don't recall the details, but I've had cases where I edited a
>> configuration file manually and Yast later overwrote my changes. I've
>> found it to be safer to just use Yast across the board, and only edit
>> those files that Yast doesn't handle.
>
> I have heard about this by people over time, yet I never have noticed it
> in the years since at least SuSE 6.3 where I have been using YaST and
> edited fstab by hand.

I've seen it happen where I've made some changes to /etc/fstab, namely
reordering the partition ordering and some other cosmetic changes
like making the various columns line up, and then had YaST reorder and
destroy the cosmetic changes. However, it's been a while since that
happened and, since I now only use the YaST partitioner during the
installation, that's not an issue. Interestingly, it do

> Sure it changes my settings but only those changes that I select to be
> changed.

One of my favourite things to do after a fresh install is to go through
the /etc/sysconfig files turning on and off various options.

> I am not saying it does not happen. I am saying that apparently either I
> am very lucky, I do not notice the changes or YaST is afraid of me and
> does not dare to change things that I do not want to change.

Maybe it's afraid of you. Have you ever wielded a debugger in anger
anywhere near YaST?


Regards,
David Bolt

--
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Am Donnerstag, 29. Oktober 2009 06:51, VWWall a écrit :

> Marcel Bruinsma wrote:
>> Am Mittwoch, 28. Oktober 2009 20:11, VWWall a écrit :
>>
>>> Strangely enough, openSUSE already has /dev/disk/by-label,
>>> which shows *all* partitions that have been given labels.
>>
>> Actually, only file system labels are in /dev/disk/by-label,
>> not the partition labels assigned upon creation with
>> parted. Partitions used as swap or raid member do
>> not show.
>>
> Those assigned partition numbers are shown at the end
> of entries in /dev/disk/by-id and also in /dev/disk/by-path.

Yes, but partitions also have a label, if you create them with the
parted command mkpart, e.g. 'mkpart SuSE_root 64 16777279'.
These labels (e.g. SuSE_root) are stored in the partition table
inside the disk label, not on the partition itself.

> I used /sbin/e2label to label partition sda11 as "PCLOS_root".
> It shows in /dev/disk/by-label as such.

That is the label of the file system created on partition sda11,
which is stored in the super block of that file system (for ext
file systems at least, other file system types might store it in
a different location of the file system).

If you erase the file system (dd if=/dev/zero of=/dev/sda11),
the file system label disappears, but the partition label will
still be there. The partition label is only removed when the
disk label (and thus the partition table) is erased (e.g.
dd if=/dev/zero of=/dev/sda).

Unfortunately, udev doesn't create links in /dev/disk/by-label
for the partition labels, only for the file system labels.

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Am Donnerstag, 29. Oktober 2009 08:45, David Bolt a écrit :

> On Thursday 29 Oct 2009 02:42, while playing with a tin of spray
> paint, Marcel Bruinsma painted this mural:
>
>> Am Mittwoch, 28. Oktober 2009 20:11, VWWall a écrit :
>>
>>> Strangely enough, openSUSE already has /dev/disk/by-label,
>>> which shows *all* partitions that have been given labels.
>>
>> Actually, only file system labels are in /dev/disk/by-label,
>> not the partition labels assigned upon creation with
>> parted. Partitions used as swap
>
> Yes they do:

You're right, the SWAPSPACE2 style swap areas, can be given
a label upon creation. That, however, is not the same thing as
the partition label, assigned with the mkpart parted command.

The swap area label assigned with mkswap is similar to a file
system label assigned with mke2fs (or tune2fs).

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Am Donnerstag, 29. Oktober 2009 08:56, David Bolt a écrit :

> On Thursday 29 Oct 2009 05:51, while playing with a tin of spray
> paint, VWWall painted this mural:
>
>> Marcel Bruinsma wrote:
>
>>> Actually, only file system labels are in /dev/disk/by-label,
>>> not the partition labels assigned upon creation with
>>> parted.
>
> Oh, I missed that part. Partitions don't have labels

Of course, partitions have a partition label, which is stored
in the partition table, which is part of the disk label.

> although they do have types, e.g. 82 is for swap, 83 for
> a Linux file system, 8E for one that's able to be a part of
> a logical volume.

Those partition types are only used for the old, deprecated
mbr format (not really a disk label). Of course, mbr doen't
provide partition labels (or 64 bit LBAs, or backup, etc.).

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On Thursday 29 Oct 2009 08:49, while playing with a tin of spray paint,
Marcel Bruinsma painted this mural:

> Am Donnerstag, 29. Oktober 2009 08:45, David Bolt a écrit :

>> Yes they do:
>
> You're right, the SWAPSPACE2 style swap areas, can be given
> a label upon creation. That, however, is not the same thing as
> the partition label, assigned with the mkpart parted command.

Which version of parted are you using? The one supplied with openSUSE
11.1, parted-1.8.8, doesn't support partition labels. There the mkpart
command is as follows:

mkpart part-type [fs-type] start end

part-type is the partition type, primary, extended or logical
fs-type is the file system type, and is optional
start and end are the start and end of the partition


Regards,
David Bolt

--
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Am Donnerstag, 29. Oktober 2009 10:35, David Bolt a écrit :

> On Thursday 29 Oct 2009 08:49, while playing with a tin of spray
> paint, Marcel Bruinsma painted this mural:
>
>> You're right, the SWAPSPACE2 style swap areas, can be given
>> a label upon creation. That, however, is not the same thing as
>> the partition label, assigned with the mkpart parted command.
>
> Which version of parted are you using? The one supplied with
> openSUSE 11.1, parted-1.8.8, doesn't support partition labels.
> There the mkpart command is as follows:
>
> mkpart part-type [fs-type] start end
>
> part-type is the partition type, primary, extended or logical
> fs-type is the file system type, and is optional
> start and end are the start and end of the partition

Version 1.8.9 (with a few local minor-bug-fixes). Older
versions (1.8.7 and 1.8. do support partition labels
too, even if the manual doesn't mention them. The
semantics of mkpart (and many other commands)
depend on the disk label type (see mklabel). The gpt
disk label partition table is linear; 'primary', 'logical'
and 'extended' are meaningless with a linear partition
table. Instead, the 'part-type' string is used as the
label of the partiton. The label can be modified with
the name command.

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Am Donnerstag, 29. Oktober 2009 11:29, Marcel Bruinsma a écrit :

> Am Donnerstag, 29. Oktober 2009 10:35, David Bolt a écrit :
>
>> On Thursday 29 Oct 2009 08:49, while playing with a tin of spray
>> paint, Marcel Bruinsma painted this mural:
>>
>>> You're right, the SWAPSPACE2 style swap areas, can be given
>>> a label upon creation. That, however, is not the same thing as
>>> the partition label, assigned with the mkpart parted command.
>>
>> Which version of parted are you using? The one supplied with
>> openSUSE 11.1, parted-1.8.8, doesn't support partition labels.
>> There the mkpart command is as follows:
>>
>> mkpart part-type [fs-type] start end
>>
>> part-type is the partition type, primary, extended or logical
>> fs-type is the file system type, and is optional
>> start and end are the start and end of the partition
>
> Version 1.8.9 (with a few local minor-bug-fixes).

Sorry, that should have been 1.9.0, of course.

> Older
> versions (1.8.7 and 1.8. do support partition labels
> too, even if the manual doesn't mention them. The
> semantics of mkpart (and many other commands)
> depend on the disk label type (see mklabel). The gpt
> disk label partition table is linear; 'primary', 'logical'
> and 'extended' are meaningless with a linear partition
> table. Instead, the 'part-type' string is used as the
> label of the partiton. The label can be modified with
> the name command.

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