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Old 01-11-2008, 06:47 PM
"Anthony E. Caudel"
 
Default Gentoo LiveUSB

I've been looking at LiveUSB's lately, specifically ones for Gentoo.
Found one on the Gentoo Documentation and another on Pendrive and
several others. Problem is that all of these do not allow you to save
changes.

Has anyone made a persistent Gentoo LiveUSB? Google hasn't helped
here. Most persistents seem to be Ubuntu and involve something called
Casper.

2nd question: I must be dense on this one so someone help me out.
Since a USB stick is seen as a hard drive, why can't I do a standard
install to it? Is it because until lately they haven't been large
enough? I'm thinking of using an 8GB one.

Tony

--
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.
-- Benjamin Franklin

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Old 01-11-2008, 07:00 PM
Alan McKinnon
 
Default Gentoo LiveUSB

On Friday 11 January 2008, Anthony E. Caudel wrote:
> 2nd question: *I must be dense on this one so someone help me out.
> Since a USB stick is seen as a hard drive, why can't I do a standard
> install to it? *Is it because until lately they haven't been large
> enough? *I'm thinking of using an 8GB one.

There's a few reasons:

1. The memory used on those devices has a limited life - about 100,000
writes for the good ones and maybe 10,000 for the bad ones. With a
standard install, frequent writes are the norm (think cache and other
similar things). This usually ends up at the same spot on the disk,
meaning your new install will last about a month if you are lucky.
There are ways around this, for instance how a LiveCD does things.

2. Booting off it is a pain. You need drivers for the entire USB stack
at boot time, which usually means a ginormous initrd.

3. Size, which you mentioned

--
Alan McKinnon
alan dot mckinnon at gmail dot com
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Old 01-11-2008, 07:27 PM
"Ritesh Kumar"
 
Default Gentoo LiveUSB

On Jan 11, 2008 3:00 PM, Alan McKinnon <alan.mckinnon@gmail.com> wrote:

On Friday 11 January 2008, Anthony E. Caudel wrote:
> 2nd question: I must be dense on this one so someone help me out.
> Since a USB stick is seen as a hard drive, why can't I do a standard

> install to it? Is it because until lately they haven't been large
> enough? I'm thinking of using an 8GB one.

There's a few reasons:

1. The memory used on those devices has a limited life - about 100,000

writes for the good ones and maybe 10,000 for the bad ones. With a
standard install, frequent writes are the norm (think cache and other
similar things). This usually ends up at the same spot on the disk,
meaning your new install will last about a month if you are lucky.

There are ways around this, for instance how a LiveCD does things.

You are right about the re-write life of flash media. However, there are filesystems which can help by not writing to the same location in the flash media again and again. I recall JFFS2 being a such flash filesystem which is available for linux.

*

2. Booting off it is a pain. You need drivers for the entire USB stack

at boot time, which usually means a ginormous initrd.

Why not compile them in the kernel?



3. Size, which you mentioned
8GB is pretty large IMHO. You should be able to fit quite some software + data on it. My *entire* gentoo distribution fits in just over 2GB... though I must confess that I am a little minimalistic.


_r
 
Old 01-11-2008, 07:29 PM
 
Default Gentoo LiveUSB

> On Friday 11 January 2008, Anthony E. Caudel wrote:
>> 2nd question: I must be dense on this one so someone help me out.
>> Since a USB stick is seen as a hard drive, why can't I do a standard
>> install to it? Is it because until lately they haven't been large
>> enough? I'm thinking of using an 8GB one.
>
> There's a few reasons:
>
> 1. The memory used on those devices has a limited life - about 100,000
> writes for the good ones and maybe 10,000 for the bad ones. With a
> standard install, frequent writes are the norm (think cache and other
> similar things). This usually ends up at the same spot on the disk,
> meaning your new install will last about a month if you are lucky.
> There are ways around this, for instance how a LiveCD does things.
>
> 2. Booting off it is a pain. You need drivers for the entire USB stack
> at boot time, which usually means a ginormous initrd.
>
> 3. Size, which you mentioned
>
> --
> Alan McKinnon
> alan dot mckinnon at gmail dot com
> --
> gentoo-user@lists.gentoo.org mailing list
>
>

Does desktop RAM get constantly refreshed while powered and it doesn't
need to keep any data when not powered?
Is that the difference?


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Old 01-11-2008, 08:11 PM
Alan McKinnon
 
Default Gentoo LiveUSB

On Friday 11 January 2008, bjlockie@lockie.ca wrote:
> > On Friday 11 January 2008, Anthony E. Caudel wrote:
> >> 2nd question: I must be dense on this one so someone help me out.
> >> Since a USB stick is seen as a hard drive, why can't I do a
> >> standard install to it? Is it because until lately they haven't
> >> been large enough? I'm thinking of using an 8GB one.
> >
> > There's a few reasons:
> >
> > 1. The memory used on those devices has a limited life - about
> > 100,000 writes for the good ones and maybe 10,000 for the bad ones.
> > With a standard install, frequent writes are the norm (think cache
> > and other similar things). This usually ends up at the same spot on
> > the disk, meaning your new install will last about a month if you
> > are lucky. There are ways around this, for instance how a LiveCD
> > does things.

> Does desktop RAM get constantly refreshed while powered and it
> doesn't need to keep any data when not powered?
> Is that the difference?

I'm not sure what you are asking - you're question is poorly framed. So
I'll answer what I think you are asking.

USB sticks use flash RAM and other non-volatile memory technologies.
It's not a magnetic disk, it does use transistors but is otherwise
completely different to desktop RAM. It's also a whole lot slower.

The operating system is almost constantly writing stuff to the disk, and
not just swap space - many apps cache information and it has to be
stored somewhere. This is not a problem for magnetic disks as they
don;t really have a limit on the number of times they can be written
to. Flash memory does, it stops working after a time. So once you write
to a memory cell say 50,000 times, it's probably useless. Trouble is,
you have no way of knowing which cells no longer work, so you have a
disk with random corruptions. This is usually considered to be a
VeryBadThing(tm).

alan



--
Alan McKinnon
alan dot mckinnon at gmail dot com
--
gentoo-user@lists.gentoo.org mailing list
 
Old 01-11-2008, 10:35 PM
"Anthony E. Caudel"
 
Default Gentoo LiveUSB

Alan McKinnon wrote:
> On Friday 11 January 2008, Anthony E. Caudel wrote:
>
>> 2nd question: I must be dense on this one so someone help me out.
>> Since a USB stick is seen as a hard drive, why can't I do a standard
>> install to it? Is it because until lately they haven't been large
>> enough? I'm thinking of using an 8GB one.
>>
>
> There's a few reasons:
>
> 1. The memory used on those devices has a limited life - about 100,000
> writes for the good ones and maybe 10,000 for the bad ones. With a
> standard install, frequent writes are the norm (think cache and other
> similar things). This usually ends up at the same spot on the disk,
> meaning your new install will last about a month if you are lucky.
> There are ways around this, for instance how a LiveCD does things.
>
> 2. Booting off it is a pain. You need drivers for the entire USB stack
> at boot time, which usually means a ginormous initrd.
>
> 3. Size, which you mentioned
>
>
OK. Then maybe a better solution for a compact portable system would be
an external HD. In the laptop size (2.5") the enclosure can just about
fit in a shirt pocket. And some of them run off the USB interface. Not
as small as a thumbdrive but close.

Tony

--
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.
-- Benjamin Franklin

--
gentoo-user@lists.gentoo.org mailing list
 
Old 01-12-2008, 10:57 AM
Florian Philipp
 
Default Gentoo LiveUSB

On Fri, 2008-01-11 at 15:27 -0500, Ritesh Kumar wrote:
> On Jan 11, 2008 3:00 PM, Alan McKinnon <alan.mckinnon@gmail.com>
> wrote:
> On Friday 11 January 2008, Anthony E. Caudel wrote:
> > 2nd question: I must be dense on this one so someone help me
> out.
> > Since a USB stick is seen as a hard drive, why can't I do a
> standard
> > install to it? Is it because until lately they haven't been
> large
> > enough? I'm thinking of using an 8GB one.
>
>
> There's a few reasons:
>
> 1. The memory used on those devices has a limited life - about
> 100,000
> writes for the good ones and maybe 10,000 for the bad ones.
> With a
> standard install, frequent writes are the norm (think cache
> and other
> similar things). This usually ends up at the same spot on the
> disk,
> meaning your new install will last about a month if you are
> lucky.
> There are ways around this, for instance how a LiveCD does
> things.
>
> You are right about the re-write life of flash media. However, there
> are filesystems which can help by not writing to the same location in
> the flash media again and again. I recall JFFS2 being a such flash
> filesystem which is available for linux.
>
>

AFAIK JFFS2 and such alike are of no use on standard USB-sticks because
they have their own system of wear levelling[1] and hide the actual
layout from the OS. They are only useful on embedded systems and stuff
like that where there is no such abstraction layer in firmware.

[1] http://en.wikipedia.org/wiki/Wear_levelling
>
 

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