pdisk question: Is changing 'Apple_Free' to 'Apple_UNIX_SVR2' destructive ?

pdisk question: Is changing 'Apple_Free' to 'Apple_UNIX_SVR2' destructive ?

Post by BK » Wed, 05 Sep 2001 05:08:27



Hi.

After trying various Linux distributions unsuccessfully on my G4, I
moved on to try MkLinux on the old 7100 and, surprise surprise, booting
off the (donwloaded) CD was taking me to the installer and everything
was exactly as described - no strange messages - everything seems just
right.

So, I intend to go ahead and do an installation. The disk I am using has
two partitions of type 'Apple_Free' at the end of the partition map, I
must have done this so years ago in anticipation I would some day
install another OS ;-)

However, Linux won't install on 'Apple_Free'. I have to change this to
'Apple_UNIX-SVR2'. The utility pdisk allows me to do that, but I don't
want to destroy the data that is on the other partitions on that disk.

There is 6.5G on that disk in the first couple of (used) partitions and
it would take me quite a while to back that up.

So, am now wondering, whether changing free space partitions (a the end
of the table) into another type *without* changing location or size is
destructive to any other (used) partitions or not. Theoretically the
other partitions should not be affected, but then again, I would rather
like to confirm this first.

Does anybody know ?

thanks
BK

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pdisk question: Is changing 'Apple_Free' to 'Apple_UNIX_SVR2' destructive ?

Post by Tom Stille » Wed, 05 Sep 2001 05:26:50




>Hi.

>After trying various Linux distributions unsuccessfully on my G4, I
>moved on to try MkLinux on the old 7100 and, surprise surprise, booting
>off the (donwloaded) CD was taking me to the installer and everything
>was exactly as described - no strange messages - everything seems just
>right.

>So, I intend to go ahead and do an installation. The disk I am using has
>two partitions of type 'Apple_Free' at the end of the partition map, I
>must have done this so years ago in anticipation I would some day
>install another OS ;-)

>However, Linux won't install on 'Apple_Free'. I have to change this to
>'Apple_UNIX-SVR2'. The utility pdisk allows me to do that, but I don't
>want to destroy the data that is on the other partitions on that disk.

>There is 6.5G on that disk in the first couple of (used) partitions and
>it would take me quite a while to back that up.

>So, am now wondering, whether changing free space partitions (a the end
>of the table) into another type *without* changing location or size is
>destructive to any other (used) partitions or not. Theoretically the
>other partitions should not be affected, but then again, I would rather
>like to confirm this first.

Don't try to change the partition types.  Use pdisk to create new
partitions of the type desired and assign them the start block and
length that corresponds to the Apple_Free partitions.  Check the
resulting partition map carefully before writing the modified partition
map.  Don't forget that somewhere along the way you will have to install
a filesystem ('mkfs') on the new partitions -- the installer may do it
for you, I don't recall.

--
Tom Stiller

PGP fingerprint =  5108 DDB2 9761 EDE5 E7E3  7BDA 71ED 6496 99C0 C7CF

 
 
 

pdisk question: Is changing 'Apple_Free' to 'Apple_UNIX_SVR2' destructive ?

Post by BK » Wed, 05 Sep 2001 07:12:50






> >Hi.

> >After trying various Linux distributions unsuccessfully on my G4, I
> >moved on to try MkLinux on the old 7100 and, surprise surprise, booting
> >off the (donwloaded) CD was taking me to the installer and everything
> >was exactly as described - no strange messages - everything seems just
> >right.

> >So, I intend to go ahead and do an installation. The disk I am using has
> >two partitions of type 'Apple_Free' at the end of the partition map, I
> >must have done this so years ago in anticipation I would some day
> >install another OS ;-)

> >However, Linux won't install on 'Apple_Free'. I have to change this to
> >'Apple_UNIX-SVR2'. The utility pdisk allows me to do that, but I don't
> >want to destroy the data that is on the other partitions on that disk.

> >There is 6.5G on that disk in the first couple of (used) partitions and
> >it would take me quite a while to back that up.

> >So, am now wondering, whether changing free space partitions (a the end
> >of the table) into another type *without* changing location or size is
> >destructive to any other (used) partitions or not. Theoretically the
> >other partitions should not be affected, but then again, I would rather
> >like to confirm this first.

> Don't try to change the partition types.  Use pdisk to create new
> partitions of the type desired and assign them the start block and
> length that corresponds to the Apple_Free partitions.

Well, there isn't really any "change" option. By "change to type
Apple_UNIX_SVR2" I meant to use the 'c' option to create a partition of
that type inside the free partition (until that point denoted as type
"Apple_Free". If I dont assign any different size nor location, then the
net effect will be that the partition changed from "Apple_Free" to
"Apple_UNIX_SVR2" even though the 'c' (for create) command was used.

My question is, whether this action will have any effect on the other
partitions. It would seem logical that they remain untouched, because
pdisk does not update any drivers nor formats the disk, but only writes
to the partition table.

Quote:>  Check the
> resulting partition map carefully before writing the modified partition
> map.

Do you mean to say that if I have the same sizes (not accidentally go
into the space of used partitions) then this will be non-destructive ?

Quote:>Don't forget that somewhere along the way you will have to install
> a filesystem ('mkfs') on the new partitions -- the installer may do it
> for you, I don't recall.

Yes, but at that point mkfs will know about the partition and it won't
do anything outside of that partition. In contrast, Drive Setup formats
the entire disk after doing any kind of modification to any partition on
the disk, which is why modifying empty space with Drive Setup will
destroy the data on existing partitions.

From what I understand pdisk doesn't do this and mkfs won't touch any
other partitions than specified. Therefore, I assume the process as
described (using pdisk to create new partition in free space) should be
non-destructive. But still I'd like to confirm this with someone who has
done this before in this way without destroying data.

thanks
rgds
BK

--

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otherwise it will be considered spam, automatically deleted and never reach me.

 
 
 

pdisk question: Is changing 'Apple_Free' to 'Apple_UNIX_SVR2' destructive ?

Post by Tom Stille » Wed, 05 Sep 2001 07:36:59








>> >Hi.

[snip]
>> >So, am now wondering, whether changing free space partitions (a the end
>> >of the table) into another type *without* changing location or size is
>> >destructive to any other (used) partitions or not. Theoretically the
>> >other partitions should not be affected, but then again, I would rather
>> >like to confirm this first.

>> Don't try to change the partition types.  Use pdisk to create new
>> partitions of the type desired and assign them the start block and
>> length that corresponds to the Apple_Free partitions.

>Well, there isn't really any "change" option. By "change to type
>Apple_UNIX_SVR2" I meant to use the 'c' option to create a partition of
>that type inside the free partition (until that point denoted as type
>"Apple_Free". If I dont assign any different size nor location, then the
>net effect will be that the partition changed from "Apple_Free" to
>"Apple_UNIX_SVR2" even though the 'c' (for create) command was used.

>My question is, whether this action will have any effect on the other
>partitions. It would seem logical that they remain untouched, because
>pdisk does not update any drivers nor formats the disk, but only writes
>to the partition table.

>>  Check the
>> resulting partition map carefully before writing the modified partition
>> map.

>Do you mean to say that if I have the same sizes (not accidentally go
>into the space of used partitions) then this will be non-destructive ?

>>Don't forget that somewhere along the way you will have to install
>> a filesystem ('mkfs') on the new partitions -- the installer may do it
>> for you, I don't recall.

>Yes, but at that point mkfs will know about the partition and it won't
>do anything outside of that partition. In contrast, Drive Setup formats
>the entire disk after doing any kind of modification to any partition on
>the disk, which is why modifying empty space with Drive Setup will
>destroy the data on existing partitions.

>From what I understand pdisk doesn't do this and mkfs won't touch any
>other partitions than specified. Therefore, I assume the process as
>described (using pdisk to create new partition in free space) should be
>non-destructive. But still I'd like to confirm this with someone who has
>done this before in this way without destroying data.

You're correct; pdisk does not touch the contents of any partition.  I
have changed the partition map on my disk many times; creating new
partitions and deleting old ones.  I have even combined partitions by
first moving the contents of the partitions so that the partitions to be
combined were contigious and then moving the contents back.  Of course,
I used the operating system (Mac OS or Linux, as necessary) to move the
contents around.

--
Tom Stiller

PGP fingerprint =  5108 DDB2 9761 EDE5 E7E3  7BDA 71ED 6496 99C0 C7CF

 
 
 

pdisk question: Is changing 'Apple_Free' to 'Apple_UNIX_SVR2' destructive ?

Post by BK » Wed, 05 Sep 2001 14:06:22




Quote:> >Yes, but at that point mkfs will know about the partition and it won't
> >do anything outside of that partition. In contrast, Drive Setup formats
> >the entire disk after doing any kind of modification to any partition on
> >the disk, which is why modifying empty space with Drive Setup will
> >destroy the data on existing partitions.

> >From what I understand pdisk doesn't do this and mkfs won't touch any
> >other partitions than specified. Therefore, I assume the process as
> >described (using pdisk to create new partition in free space) should be
> >non-destructive. But still I'd like to confirm this with someone who has
> >done this before in this way without destroying data.

> You're correct; pdisk does not touch the contents of any partition.  I
> have changed the partition map on my disk many times; creating new
> partitions and deleting old ones.  I have even combined partitions by
> first moving the contents of the partitions so that the partitions to be
> combined were contigious and then moving the contents back.  Of course,
> I used the operating system (Mac OS or Linux, as necessary) to move the
> contents around.

Ah that's great news, thank you.

Just edited the partition table and turned the free space into Linux
partitions, also cleaned out one of the HFS partitions and used half of
it to create Linux swap space and the other half I recreated a smaller
HFS partition. After reboot the MacOS automatically picked up on that
"new" HFS partition and asked if I wanted to format it. No harm done to
any of the other partitions. I am very pleased.

thanks again for your help.

rgds
BK

--

ATTENTION! Email to this address *must* contain "USENET" in the subject line
otherwise it will be considered spam, automatically deleted and never reach me.

 
 
 

pdisk question: Is changing 'Apple_Free' to 'Apple_UNIX_SVR2' destructive ?

Post by Tom Stille » Wed, 05 Sep 2001 21:11:48




>Just edited the partition table and turned the free space into Linux
>partitions, also cleaned out one of the HFS partitions and used half of
>it to create Linux swap space and the other half I recreated a smaller
>HFS partition. After reboot the MacOS automatically picked up on that
>"new" HFS partition and asked if I wanted to format it. No harm done to
>any of the other partitions. I am very pleased.

>thanks again for your help.

Glad to help.

--
Tom Stiller

PGP fingerprint =  5108 DDB2 9761 EDE5 E7E3  7BDA 71ED 6496 99C0 C7CF

 
 
 

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