Install to external HDD using GRUB2

English Install/Boot/Login
#1

Hi there,

I’m pretty green considering Unix, but I planned on installing OPENsuse 13.1 to an external HDD to test the performance on my Netbook. For this reason, I would like to keep my Windows-Installation on my internal HDD untouched, including the bootloader.

I managed to find this guide on how to configure GRUB

https://en.opensuse.org/SDB:Installation_on_external_hard_drive

but have been wondering, if this was also possible using GRUB2 (and still applicable to OPENsuse 13.1)

Or is there no reason whatsoever to use GRUB2?

#2

openSUSE 13.1 (and earlier) uses GRUB2 by default.

#3

openSUSE 13.1 (and earlier) uses GRUB2 by default.

Yes, I’m aware of that, but how to configure GRUB2 to boot from external HDD without changing the internal?

#4

On 2014-08-03 11:56 (GMT) harnd composed:

> I’m pretty green considering Unix, but I planned on installing OPENsuse
> 13.1 to an external HDD to test the performance on my Netbook. For this
> reason, I would like to keep my Windows-Installation on my internal HDD
> untouched, including the bootloader.

> I managed to find this guide on how to configure GRUB

> https://en.opensuse.org/SDB:Installation_on_external_hard_drive

Note that that page doesn’t distinguish different types of external drives.
Those of us using physically external drives that have eSATA connections
instead of USB need not pay much attention generally to the word “external”.
Depending on the motherboard’s controller configuration, eSATA is likely to
be just another HD with nothing distinguishing it from the internal HD except
device/boot order.

Here’s another URI you may not have noticed:
https://old-en.opensuse.org/Bugs/grub#How_does_a_PC_boot_.2F_How_can_I_set_up_a_working_GRUB.3F

> but have been wondering, if this was also possible using GRUB2 (and
> still applicable to OPENsuse 13.1)

> Or is there no reason whatsoever to use GRUB2?

13.1 provides an option to use Grub Legacy. I have over a dozen 13.1
installations. None of them use Grub2. It’s up to you to decide what’s best
for you. Most people don’t need what Grub2 has that Grub Legacy does not.

Grub2 upstream policy is that Grub belongs on the MBR. My own policy is that
no bootloader ever goes on the MBR except one which Windows will not replace
if Windows is installed.

Whether to choose one or the other depends in part on whether you even care
how booting happens. If not, just accept the Grub2 default. If you want to
get into the process, many factors play into making the better choice, one of
which is which instructions you find easiest to follow, and another of which
is whether you find conceptually simpler using Grub’s shell to do your
tweaking, or want to depend on scripts to do your work. Scripts depend on
proper mounting and/or chrooting, while the shell works even if no disks are
mounted. Being newer and bigger both physically and logically, Grub2’s shell
is more complicated to learn.

The wise are known for their understanding, and pleasant
words are persuasive.

Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata *** http://fm.no-ip.com/

#5

On 2014-08-03 12:46 (GMT) harnd composed:

>> openSUSE 13.1 (and earlier) uses GRUB2 by default.

> Yes, I’m aware of that, but how to configure GRUB2 to boot from external
> HDD without changing the internal?

Same as with Grub Legacy. Make it pretend/assume there is only the external
HD, and have the machine choose to boot from the external when that’s what
you want.

The wise are known for their understanding, and pleasant
words are persuasive.

Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata *** http://fm.no-ip.com/

#6

Like mrmazda my idea is that “internal” and “external” are loosely used terms where people do not realy know precisely what they mean and thus using them withourt further specification may lead to misunderstandings.

When it means a disk that is either inside the metal box or standing beside it, that may be important to decide how many physical space the sytem takes on the table or in the room, but for the system and the operating system this has no significance.

Some people seem to think that “internal” means PCI connected and “external” means USB connected. For the hardware that is of course different, as it is for the operating system on the level of drivers, but once it comes to the level of device files (disks and partitions as found in /dev) there is no difference anymore (after all, one of the main task of an operating system is to hide hardware from higher level programming and the user).

But when you in fact mean with “external” that you want to connect/deconnect the device at will, that is different. Soecialy when you want to boot from it. Because it could be that the system will not boot from any disk when that particular disk is not connected.

So IMHO only in the last case you must take any precautions. But when the disk is always connected the difference between “internal” and “external” is of no influence.

#7

I’ve installed 13.1 and factory (pre-release 13.2) to an external disk, using grub2. I’ll add that these were all to the same external disk. I’m not keeping all of those different version. I’ve just been doing test installs, and sometimes I do that to an external drive.

Here’s my detailed description of installing 13.1:
Installing opensuse on an external drive — MBR version

The section on “Boot configuration” is probably what you are looking for. My more recent installs (of factory) have been rather routine, as long as I followed what I describe for “Boot configuration”.

#8

On 2014-08-03 13:16 (GMT) hcvv composed:

> …but once it comes to the level of device files (disks and partitions as
> found in /dev) there is no difference anymore (after all, one of the
> main task of an operating system is to hide hardware from higher level
> programming and the user).
…
> when the disk is always connected the difference between “internal” and
> “external” is of no influence.

Possibly true if the issue is USB3 vs. eSATA, but for USB1 or USB2 vs. eSATA,
throughput makes a bit difference to anyone using it for boot or working with
large files. eSATA is typically somewhere in the vicinity of at least 2.5X as
fast as USB2. Actual example:

7200 RPM 2TB Seagate:
Model=ST2000DM001-1CH164, FwRev=CC27, SerialNo=W1E54Y73
UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
Drive conforms to: Reserved: ATA/ATAPI-4,5,6,7

Installed in:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182247

hdparm -t:

connected as /dev/sdb via eSATA on NM10/ICH7 SATA interface:
Timing buffered disk reads: 536 MB in 3.01 seconds = 178.34 MB/sec

connected as /dev/sdb via USB2 on NM10/ICH7 EHCI interface:
Timing buffered disk reads: 106 MB in 3.03 seconds = 34.95 MB/sec

For this example, eSATA is reading the same device without benefit of cache
at 5.1X the speed of USB2.

IOW, for booting from external HD, you should prefer a connection faster than
USB2 if performance on a level similar to an internal HD is wanted.

The wise are known for their understanding, and pleasant
words are persuasive.

Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata *** http://fm.no-ip.com/

#9

We did not talk about performace at all. The subject was to get a better definition on what the OP “sees before his eyes” when he uses the words “internal” and " external" so that we may ubderstand better what he tries to tell us.

#10

On 2014-08-03 15:57 (GMT-0400) Felix Miata composed:

> On 2014-08-03 13:16 (GMT) hcvv composed:
>
>> …but once it comes to the level of device files (disks and partitions as
>> found in /dev) there is no difference anymore (after all, one of the
>> main task of an operating system is to hide hardware from higher level
>> programming and the user).
> …
>> when the disk is always connected the difference between “internal” and
>> “external” is of no influence.
>
> Possibly true if the issue is USB3 vs. eSATA, but for USB1 or USB2 vs. eSATA,
> throughput makes a bit difference to anyone using it for boot or working with
> large files. eSATA is typically somewhere in the vicinity of at least 2.5X as
> fast as USB2. Actual example:
>
> 7200 RPM 2TB Seagate:
> Model=ST2000DM001-1CH164, FwRev=CC27, SerialNo=W1E54Y73
> UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
> Drive conforms to: Reserved: ATA/ATAPI-4,5,6,7

> Installed in:
> http://www.newegg.com/Product/Product.aspx?Item=N82E16817182247

> # hdparm -t:

> connected as /dev/sdb via eSATA on NM10/ICH7 SATA interface:
> Timing buffered disk reads: 536 MB in 3.01 seconds = 178.34 MB/sec

> connected as /dev/sdb via USB2 on NM10/ICH7 EHCI interface:
> Timing buffered disk reads: 106 MB in 3.03 seconds = 34.95 MB/sec

> For this example, eSATA is reading the same device without benefit of cache
> at 5.1X the speed of USB2.

> IOW, for booting from external HD, you should prefer a connection faster than
> USB2 if performance on a level similar to an internal HD is wanted.

A different HD, 5400 RPM laptop drive, connected through:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182197

Model=WDC WD5000LPVX-00V0TT0, FwRev=01.01A01, SerialNo=WD-WX11A54M6007
UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6
Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6,7

hdparm -t

connected as /dev/sdb via eSATA on ICH7R interface:
Timing buffered disk reads: 286 MB in 3.01 seconds = 94.88 MB/sec

connected as /dev/sdb via USB2 interface:
Timing buffered disk reads: 96 MB in 3.02 seconds = 31.75 MB/sec

For this example, eSATA is reading the same device without benefit of cache
at 2.99X the speed of USB2.

The wise are known for their understanding, and pleasant
words are persuasive.

Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata *** http://fm.no-ip.com/