[gentoo-user] Preparing a shared USB stick

[gentoo-user] Preparing a shared USB stick

[Chris Stankevitz]

Hello,

Please consider a USB "stick" that is unformatted but is to be used by
multiple people/machines.  Ideally your instructions will work for all
people/os/WM, but if necessary please assume that everyone is running
gnome under linux

1. How should I prepare this device so that it can be plugged into any
machine and will be writable by anyone?  I suspect the answer will
involve words like fdisk, mkfs.xxx, mkdir/mount, chmod/chown.  I'm
most interested in the chmod/chown part.

2. How can I prepare the device so that files/directories added by
people in the future will continue to be writable by anyone?

3. How can I ensure that all files will appear to have the same owner;
or, if this is not important, can you explain why it should not be a
problem.

And of course if you can refer me to a document that explains this I'm
happy to read it.

Thank you,

Chris

Re: [gentoo-user] Preparing a shared USB stick

[Mateusz Kowalczyk]

On 02/01/14 23:02, Chris Stankevitz wrote:
> Hello,
>
> Please consider a USB "stick" that is unformatted but is to be used by
> multiple people/machines.  Ideally your instructions will work for all
> people/os/WM, but if necessary please assume that everyone is running
> gnome under linux

Well, if it ideally should work across multiple operating systems,
you're probably stuck with FAT32 or similar due to Windows.

> 1. How should I prepare this device so that it can be plugged into any
> machine and will be writable by anyone?  I suspect the answer will
> involve words like fdisk, mkfs.xxx, mkdir/mount, chmod/chown.  I'm
> most interested in the chmod/chown part.

If you go with FAT, there's no notion of ownership (I believe) so it's
not a problem. If you don't, I still don't think chmod/chown matters
as long as the user has the permissions to write to the stick when
mounted on their own machine. I might be wrong though!

> 2. How can I prepare the device so that files/directories added by
> people in the future will continue to be writable by anyone?

Likewise, I think they'll be able to as long as they have the
permission to write to the mounted stick _on their own machine_.

> 3. How can I ensure that all files will appear to have the same owner;
> or, if this is not important, can you explain why it should not be a
> problem.

I think it's not a problem, at least not with FAT.

> And of course if you can refer me to a document that explains this I'm
> happy to read it.
>
> Thank you,
>
> Chris
>

I'm not an expert but hopefully this helps to at least steer you in
the right direction. I used multiple USB sticks across multiple
machines across multiple systems in the past and I never had any
ownership concerns that you do. The only issues were if one of the
systems couldn't read the file format used.

--
Mateusz K.

Re: [gentoo-user] Preparing a shared USB stick

[Francisco Ares]

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2014/1/2 Mateusz Kowalczyk <fuuzetsu@fuuzetsu.co.uk>

> On 02/01/14 23:02, Chris Stankevitz wrote:
> > Hello,
> >
> > Please consider a USB "stick" that is unformatted but is to be used by
> > multiple people/machines.  Ideally your instructions will work for all
> > people/os/WM, but if necessary please assume that everyone is running
> > gnome under linux
>
> Well, if it ideally should work across multiple operating systems,
> you're probably stuck with FAT32 or similar due to Windows.
>
> > 1. How should I prepare this device so that it can be plugged into any
> > machine and will be writable by anyone?  I suspect the answer will
> > involve words like fdisk, mkfs.xxx, mkdir/mount, chmod/chown.  I'm
> > most interested in the chmod/chown part.
>
> If you go with FAT, there's no notion of ownership (I believe) so it's
> not a problem. If you don't, I still don't think chmod/chown matters
> as long as the user has the permissions to write to the stick when
> mounted on their own machine. I might be wrong though!
>
> > 2. How can I prepare the device so that files/directories added by
> > people in the future will continue to be writable by anyone?
>
> Likewise, I think they'll be able to as long as they have the
> permission to write to the mounted stick _on their own machine_.
>
> > 3. How can I ensure that all files will appear to have the same owner;
> > or, if this is not important, can you explain why it should not be a
> > problem.
>
> I think it's not a problem, at least not with FAT.
>
> > And of course if you can refer me to a document that explains this I'm
> > happy to read it.
> >
> > Thank you,
> >
> > Chris
> >
>
> I'm not an expert but hopefully this helps to at least steer you in
> the right direction. I used multiple USB sticks across multiple
> machines across multiple systems in the past and I never had any
> ownership concerns that you do. The only issues were if one of the
> systems couldn't read the file format used.
>
> --
> Mateusz K.
>
>

As far as I know, in a Gentoo system, any user in the group "disk" will be
able to read/write to any USB stick plugged into the computer, with no
ownership to any written file. In Linux (at least), as users are internally
treated as numbers, those would not match from one system to another, so
there is no meaning in a user owning a file in a removable device.

I would suggest to format tat USB stick using NTFS, as it will be possible
to use its compression (to write a compressed file is, AFAIK, exclusive to
Windows, but any NTFS file, compressed or not, is readable under Linux -
including Android, I already tested it, and also my Blu-Ray player with USB
connection is able to read my NTFS formated USB stick).

Hope this helps
Francisco

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Re: [gentoo-user] Preparing a shared USB stick

[Alan McKinnon]

On 03/01/2014 01:02, Chris Stankevitz wrote:
> Hello,
> 
> Please consider a USB "stick" that is unformatted but is to be used by
> multiple people/machines.  Ideally your instructions will work for all
> people/os/WM, but if necessary please assume that everyone is running
> gnome under linux
> 
> 1. How should I prepare this device so that it can be plugged into any
> machine and will be writable by anyone?  I suspect the answer will
> involve words like fdisk, mkfs.xxx, mkdir/mount, chmod/chown.  I'm
> most interested in the chmod/chown part.
> 
> 2. How can I prepare the device so that files/directories added by
> people in the future will continue to be writable by anyone?
> 
> 3. How can I ensure that all files will appear to have the same owner;
> or, if this is not important, can you explain why it should not be a
> problem.
> 
> And of course if you can refer me to a document that explains this I'm
> happy to read it.



Just go with FAT and automounting by the DE.

It's a removeable stick, the user has it in their hands so the entire
concept of security is instantly null and void right there. Forget all
about /etc/fstab, mount options user and user, mount options mask, fmask
and dmask. Instead, put each user that needs to use it in the plugdev or
disk group as appropriate and let the DE do the heavy lifting; and
remove from fstab anything and everything related to removeable USB sticks.

If you let the DE do the automounting for you, you get a filemanager
window (dolphin, nautilus and friends) and the contents of the stick are
visible right there, ready to use, all set up correctly.

DO NOT USE NTFS ON A STICK. The driver has been reverse-engineered and
there is no guarantee that writing to it under anything that isn't
Windows will work. FAT is a published standard and we all know how it works.

tl;dr

You don't need chown/chmod at all. FAT has no concept of owner and
permissions, so the kernel fudges these. Basically, when mounting the
stick it pretends every file on it is owned by the user that mounted it
and everything has permissions 777, regardless of who plugged it in.
Considering the nature of a USB stick, this is almost always what you want.

Don't bother partitioning the stick either, Windows treats them as one
huge floppy and so should you. You will normally only ever have one
partition anyway, so why have any at all? The code supports this. To
format it in Linux, do this:

mkfs.vfat -I /dev/<whatever>

Stay far away from /etc/fstab. That file was designed ages ago for
permanent mounts, like / and /usr and /home. To work properly, you must
be able to uniquely identify any device and never get it confused. You
just can't do that with sticks, not even with fs labels, and you
certainly don't want to hand-edit UUIDs. And you still have to deal with
users having different uids on each machine. Ugh. The DE just makes all
this hassle go away.

If your sticks are larger than 32G, you might want to use exFAT instead
of FAT - think of it as FAT that can deal with huge disks properly:

emerge sys-fs/fuse-exfat

you will need FUSE support in your kernel for this.


-- 
Alan McKinnon
alan.mckinnon@gmail.com

Re: [gentoo-user] Preparing a shared USB stick

[Neil Bothwick]

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On Fri, 3 Jan 2014 00:31:27 -0200, Francisco Ares wrote:

> As far as I know, in a Gentoo system, any user in the group "disk" will
> be able to read/write to any USB stick plugged into the computer, with
> no ownership to any written file. In Linux (at least), as users are
> internally treated as numbers, those would not match from one system to
> another, so there is no meaning in a user owning a file in a removable
> device.

This is incorrect. File ownership is a domain of the filesystem, it is
held in the file's metadata. If you use a filesystem that supports
ownership, like ext*, you will end up with a non-portable stick. Belog to
the disk group only allows access to the dev node, not the files on the
disk.

Stick with FAT, where thereis no ownership so Linux pretend all files
are owned by whoever mounted the drive.


-- 
Neil Bothwick

Multitasking: Reading in the bathroom.

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[gentoo-user] Re: Preparing a shared USB stick

[James]

Alan McKinnon <alan.mckinnon <at> gmail.com> writes:


> Just go with FAT and automounting by the DE.


Only thing I would add is be "aware" of 

Fat 12/16/32 as FAT.....

http://en.wikipedia.org/wiki/File_Allocation_Table


hth,
James

Re: [gentoo-user] Preparing a shared USB stick

[Chris Stankevitz]

On Thu, Jan 2, 2014 at 10:45 PM, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
> You don't need chown/chmod at all. FAT has no concept of owner and
> permissions, so the kernel fudges these. Basically, when mounting the
> stick it pretends every file on it is owned by the user that mounted it
> and everything has permissions 777, regardless of who plugged it in.
> Considering the nature of a USB stick, this is almost always what you want.

Alan,

Thank you very much this is exactly what I needed to understand.  It
sounds like trying to manage a shared disk/stick with ext* would be a
PITA.

Chris

Re: [gentoo-user] Preparing a shared USB stick

[Chris Stankevitz]

On Fri, Jan 3, 2014 at 1:16 AM, Neil Bothwick <neil@digimed.co.uk> wrote:
> Stick with FAT, where thereis no ownership so Linux pretend all files
> are owned by whoever mounted the drive.

Neil,

Thank you.

Chris

Re: [gentoo-user] Preparing a shared USB stick

[Alan McKinnon]

On 05/01/2014 01:31, Chris Stankevitz wrote:
> On Thu, Jan 2, 2014 at 10:45 PM, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
>> You don't need chown/chmod at all. FAT has no concept of owner and
>> permissions, so the kernel fudges these. Basically, when mounting the
>> stick it pretends every file on it is owned by the user that mounted it
>> and everything has permissions 777, regardless of who plugged it in.
>> Considering the nature of a USB stick, this is almost always what you want.
> 
> Alan,
> 
> Thank you very much this is exactly what I needed to understand.  It
> sounds like trying to manage a shared disk/stick with ext* would be a
> PITA.


yes, it is, very much so


FAT was designed for MS-DOS where you put a floppy in the drive and you
had full access to everything on it. There was no need to implement
security. And usually this is exactly what you want for USB sticks.

ext* and all the other Unix filesystems were designed to cope well with
multi-user, multi-process environments where the disk is fixed and a
permanent part of the computer infrastructure. Security was very much
part of the design. (OK, to be truthful in the early days it wasn't
security, the idea was just to let everyone keep their stuff separate
and not have everyone clobber everyone else's files, but that translates
directly to a security model). In almost all cases this is not what you
want for USB sticks.

If you DO need security like eg sharing top-secret marketing strategy
docs with the CEO :-) then you just encrypt the drive with a shared
secret. There are many such packages out there, pick one that encrypts
the entire disk without needing to know the fs structure underneath. But
somehow I don't think *that* is what you are looking for :-)


-- 
Alan McKinnon
alan.mckinnon@gmail.com

[gentoo-user] Re: Preparing a shared USB stick

[walt]

On 01/04/2014 03:44 PM, Alan McKinnon wrote:

> FAT was designed for MS-DOS where you put a floppy in the drive and you
> had full access to everything on it. There was no need to implement
> security.

I think the operative phrase is "there was no need" back when Gates and
Allen trained the world to accept failure as good enough.

Re: [gentoo-user] Re: Preparing a shared USB stick

[Alan McKinnon]

On 05/01/2014 02:42, walt wrote:
> On 01/04/2014 03:44 PM, Alan McKinnon wrote:
> 
>> FAT was designed for MS-DOS where you put a floppy in the drive and you
>> had full access to everything on it. There was no need to implement
>> security.
> 
> I think the operative phrase is "there was no need" back when Gates and
> Allen trained the world to accept failure as good enough.
> 
> 
> 
> 


I don't think so. This was back in the early 80s remember and PCs were a
new novelty. The thing to compare them to was paper records and we all
know bits of paper have no inherent security attributes. If you want to
secure them, keep them in a space with a lock. To secure a PC and it's
floppies, store them in a space with a lock.

And then there's the hardware, those things ran on 8086 chips. Not bad
for the time, but not exactly heavy on cpu grunt.

You can't seriously be pushing the line that MS promotes failure. gates
and Allen had the balls to get a working pc to market that put one on
every office desk and made computing ubiquitous. Sure, if they didn't do
it someone else would have, but they are the guys that did when no-one
else had managed. Think Amstrad, Sinclair, early Commodore. Even the
Beeb, awesome as it was, tanked completely.

It's all very easy for us to sit back today and play monday morning
fullback but in those days hardly anyone had a clue about security or
how to do it. The guys who did know were the mainframe and mini guys,
and that model didn't translate to what the PC was meant for.

Hey, I like to bash MS as much as the next guy (IE6 is a crime that
shall never be forgiven) but I do think we should bash MS for things
they deserve, not so much for things they don't.


-- 
Alan McKinnon
alan.mckinnon@gmail.com

Re: [gentoo-user] Preparing a shared USB stick

[Chris Stankevitz]

On Sat, Jan 4, 2014 at 3:44 PM, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
> On 05/01/2014 01:31, Chris Stankevitz wrote:
>> On Thu, Jan 2, 2014 at 10:45 PM, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
>> It
>> sounds like trying to manage a shared disk/stick with ext* would be a
>> PITA.
>
> yes, it is, very much so

I wonder what something like the Synology DS212j uses.  It allows for
ACLs (implying ext* or NTFS under the hood); however, it has a USB
cable (implying trouble-free plugging into many different machines).

I bet if you use it on the network with the ACLs and subsequently
write from a few machines with the USB cable... the thing gets
FUBAR-ed.

Chris

[gentoo-user] Re: Preparing a shared USB stick

[walt]

On 01/04/2014 05:21 PM, Alan McKinnon wrote:
> On 05/01/2014 02:42, walt wrote:
>> On 01/04/2014 03:44 PM, Alan McKinnon wrote:
>>
>>> FAT was designed for MS-DOS where you put a floppy in the drive and you
>>> had full access to everything on it. There was no need to implement
>>> security.
>>
>> I think the operative phrase is "there was no need" back when Gates and
>> Allen trained the world to accept failure as good enough.
>>
>>
>>
>>
> 
> 
> I don't think so. This was back in the early 80s remember and PCs were a
> new novelty. The thing to compare them to was paper records and we all
> know bits of paper have no inherent security attributes. If you want to
> secure them, keep them in a space with a lock. To secure a PC and it's
> floppies, store them in a space with a lock.
> 
> And then there's the hardware, those things ran on 8086 chips. Not bad
> for the time, but not exactly heavy on cpu grunt.
> 
> You can't seriously be pushing the line that MS promotes failure. gates
> and Allen had the balls to get a working pc to market that put one on
> every office desk and made computing ubiquitous. Sure, if they didn't do
> it someone else would have, but they are the guys that did when no-one
> else had managed. Think Amstrad, Sinclair, early Commodore. Even the
> Beeb, awesome as it was, tanked completely.
> 
> It's all very easy for us to sit back today and play monday morning
> fullback but in those days hardly anyone had a clue about security or
> how to do it. The guys who did know were the mainframe and mini guys,
> and that model didn't translate to what the PC was meant for.
> 
> Hey, I like to bash MS as much as the next guy (IE6 is a crime that
> shall never be forgiven)

LOL!

> but I do think we should bash MS for things
> they deserve, not so much for things they don't.

Okay, okay, you're absolutely right about the early-early days.

I'm thinking about the era when GM's CEO complained that if GM made
cars the way Bill made software (I paraphrase) then tow-truck drivers
would be millionaires.

For several years the IT people where I work have been making hundreds
of lives a living hell because failure is greeted every day with a shrug
and a hostile apology,

I *do* blame M$ for setting the bar that low, though not in the early
days, I agree.

[gentoo-user] Re: Preparing a shared USB stick

[walt]

On 01/04/2014 05:21 PM, Alan McKinnon wrote:

> It's all very easy for us to sit back today and play monday morning
> fullback

:)

I know as little about, um, Celtic football as you know about American
football, I see.

I know sod-all about sports from anywhere, but even I know that the
phrase is "monday morning quarterback".

All in the spirit of cross-cultural fellowship, of course :)

Re: [gentoo-user] Re: Preparing a shared USB stick

[Alan McKinnon]

On 05/01/2014 23:26, walt wrote:
> I'm thinking about the era when GM's CEO complained that if GM made
> cars the way Bill made software (I paraphrase) then tow-truck drivers
> would be millionaires.
> 
> For several years the IT people where I work have been making hundreds
> of lives a living hell because failure is greeted every day with a shrug
> and a hostile apology,


I know that attitude very well; I'm usually the guy shrugging about
software, along with a

"what the fuck do you want me to do about it? I didn't write that code"

where "that code" is often in-house Ops stuff written years ago in php.
I'm trying hard to get rid of the attitude, not succeeding much though.

But I do think that MS's track record is not really a result of malice,
it's more a case of "ship it when it's good enough to run, not when it's
correct" for varying definitions of good enough and on how many machines
it was good enough.

I'll give you a parallel in the Linux world:

gtk+/gnome vs efl/e18

GTK is the worst possible of all GUI toolkit. It's getting better but by
god early versions sucked hugely. Ever looked into what it takes to
write a gtk-engine for themeing?And as for Gnome they can never make up
their damn mind how the back-end comms are going to work. We've been
through endless iterations of corba and Miguel trying to get mono forced
in, now I think they settled on dbus. What was that Corba thing called?
Bonobo? But it ran, and ran good enough to be used.

Contrast efl and e18. That project strives to be correct and raster
refused to release anything until it was better than correct. For ten
years it sat in cvs only, until one day MikeB stepped up and said "hell
or high water we release what we have 21 Dec 2013". I think there would
be arguments behind the scenes but no matter, on that day e17 and efl
was released. One year later exactly e18 was released. It's a beautiful
toolkit, you don't have to touch any code at all to theme it and it's
slick, neat and runs on just about anything with a cpu. Even does
amazing amounts of OpenGL smoothly in software if you need to. But who
uses it?

MS:Gnome::<not MS>:efl-e18

But I'm still not going to forgive Bill for IE6 :-)

-- 
Alan McKinnon
alan.mckinnon@gmail.com

Re: [gentoo-user] Re: Preparing a shared USB stick

[Alan McKinnon]

On 05/01/2014 23:50, walt wrote:
> On 01/04/2014 05:21 PM, Alan McKinnon wrote:
> 
>> It's all very easy for us to sit back today and play monday morning
>> fullback
> 
> :)
> 
> I know as little about, um, Celtic football as you know about American
> football, I see.
> 
> I know sod-all about sports from anywhere, but even I know that the
> phrase is "monday morning quarterback".
> 
> All in the spirit of cross-cultural fellowship, of course :)

Yeah, you're right.

I live in a country where the national religion is Rugby, none of that
weeny nonsense with helmets and pads - we go in with bare hands. The guy
at the back usually built like a brick shit-house and with a good
kicking foot is never called a "quarterback"

Old naming habits die hard :-)


-- 
Alan McKinnon
alan.mckinnon@gmail.com