using the same repo with different OS

using the same repo with different OS

[Stefano Spinucci]

I have my repos on a USB key (fat32 fs) and I work with git under
linux and windows (maybe also Solaris in the future).

Considering also the new MinGW port, should I use a different repo for
every OS I work with???

Are planned/expected OS-specific files in the repo preventing me to
use the same whenever I'm working???

thanks in advance

---
Stefano Spinucci

Re: using the same repo with different OS

[Stefano Spinucci]

On 2/25/07, Stefano Spinucci <virgo977virgo@gmail.com> wrote:
> Are planned/expected OS-specific files in the repo preventing me to
> use the same *whenever* I'm working???

:-(

obviously, I mean "*wherever* I'm working???"

---
Stefano Spinucci

Re: using the same repo with different OS

[Johannes Schindelin]

Hi,

On Sun, 25 Feb 2007, Stefano Spinucci wrote:

> I have my repos on a USB key (fat32 fs) and I work with git under
> linux and windows (maybe also Solaris in the future).
> 
> Considering also the new MinGW port, should I use a different repo for 
> every OS I work with???

You don't need to. But remember that the stat informations are likely to 
be borked. For example, when you do a "git-status" on a sizable working 
tree on that stick, it will take a long, long time whenever you switch 
OSes. Basically the same amount of time as if git did not have an index!

> Are planned/expected OS-specific files in the repo preventing me to use 
> the same whenever I'm working???

It could be possible that the index is saved in a slightly different 
format, due to different alignment strategies. Maybe 64-bit vs 32-bit has 
differences there. I have no idea.

Ciao,
Dscho

Re: using the same repo with different OS

[Junio C Hamano]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> It could be possible that the index is saved in a slightly different 
> format, due to different alignment strategies. Maybe 64-bit vs 32-bit has 
> differences there. I have no idea.

As far as I am aware of, there should be no such difference,
although we probably rely on int being 32 and long being 64
bit.  We do store our numbers in network byte order.

However, did somebody say FAT-32?  I seem to recall that that
filesystem lacks uid/gid, so I am reasonably sure there would be
different return values for the same path from lstat(2) between
git on Cygwin/MinGW and on Linux that mounts the same filesystem
using vfat driver with different uid= & gid= mount options.
That difference which would make the paths stat-dirty.

Also there is the problem of i-num we discussed lately.  The
i-num we get for the same path from lstat(2) can be different
when same filesystem is mounted by different operating systems
(remember that NTFS on Linux and Cygwin?).

So even though file format of the index may be designed and
implemented to be portable, it might not be practical to use
the same physical repository from different OSes, depending on
the combination of things.

Re: using the same repo with different OS

[Johannes Schindelin]

Hi,

On Sun, 25 Feb 2007, Junio C Hamano wrote:

> So even though file format of the index may be designed and implemented 
> to be portable, it might not be practical to use the same physical 
> repository from different OSes, depending on the combination of things.

Yes.

However, in the case of a _bare_ repo, which is meant purely to transport 
(possibly huge) changes from A to B, a USB stick can be used _without_ 
problems. I do that myself quite often.

Ciao,
Dscho

Re: using the same repo with different OS

[Junio C Hamano]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> However, in the case of a _bare_ repo, which is meant purely to transport 
> (possibly huge) changes from A to B, a USB stick can be used _without_ 
> problems. I do that myself quite often.

I think we are in agreement, but read the thread again.  You
brought up the index and my response is only about the
portability of the index.  Of course, the index does not matter
in a bare repository ;-)

Re: using the same repo with different OS

[Stefano Spinucci]

I noticed today that my notes about compiling Git on cygwin to work
with FAT32 (export NO_MMAP=1) on the Wiki page WindowsInstall were
removed.

Than I'm asking how you'd setup repos to work on some linux/windows
machines, transferring data only with an USB disk.

* current repos scenario *
r1.linux -> on fat32
r2.windows -> on fat32

* proposed (better???) repos scenario *
r1.lin -> on ext3 (partition 1)
r1.lin -> on fat32 (partition 2) mirrored with rsync from linux
r2.win -> on fat32 (partition 2) mirrored with cwrsync from windows
r2.win -> on ntfs (partition 3)


bye, and thanks for the wonderful tool git is!

---
Stefano Spinucci

Re: using the same repo with different OS

[Shawn O. Pearce]

Stefano Spinucci <virgo977virgo@gmail.com> wrote:
> I noticed today that my notes about compiling Git on cygwin to work
> with FAT32 (export NO_MMAP=1) on the Wiki page WindowsInstall were
> removed.

That was me.  NO_MMAP=1 is now the default on Cygwin.
 
> Than I'm asking how you'd setup repos to work on some linux/windows
> machines, transferring data only with an USB disk.

Just create a bare repository on the USB stick and push/fetch to it.
It won't have a checkout directory or an index, the two sticking
points with mmap() on Windows and with a FAT32 filesystem being
accessed through Git by both Linux and Windows.

-- 
Shawn.

Re: using the same repo with different OS

[Stefano Spinucci]

On 2/28/07, Shawn O. Pearce <spearce@spearce.org> wrote:
>
> Stefano Spinucci <virgo977virgo@gmail.com> wrote:
> > Than I'm asking how you'd setup repos to work on some linux/windows
> > machines, transferring data only with an USB disk.
>
> Just create a bare repository on the USB stick and push/fetch to it.
> It won't have a checkout directory or an index, the two sticking
> points with mmap() on Windows and with a FAT32 filesystem being
> accessed through Git by both Linux and Windows.

Needing to have my repos backupped and only on fat32 usb keys, I was
thinking to have the following layout:
on usb key one --> repo.linux
on usb key two --> repo.win

Then, on repo.win, I'll do:
# before daily work on windows
fetch from repo.linux
# after daily work on windows
push to repo.linux

Otherwise, on repo.linux:
# before nightly work on linux
fetch from repo.windows
# after nightly work on linux
push to repo.windows

It's possible, or I need a third bare repository between windows and linux ???

thanks

---
Stefano Spinucci

Re: using the same repo with different OS

[Johannes Schindelin]

Hi,

On Mon, 12 Mar 2007, Stefano Spinucci wrote:

> On 2/28/07, Shawn O. Pearce <spearce@spearce.org> wrote:
> > 
> > Stefano Spinucci <virgo977virgo@gmail.com> wrote:
> > > Than I'm asking how you'd setup repos to work on some linux/windows
> > > machines, transferring data only with an USB disk.
> > 
> > Just create a bare repository on the USB stick and push/fetch to it.
> > It won't have a checkout directory or an index, the two sticking
> > points with mmap() on Windows and with a FAT32 filesystem being
> > accessed through Git by both Linux and Windows.
> 
> Needing to have my repos backupped and only on fat32 usb keys, I was
> thinking to have the following layout:
> on usb key one --> repo.linux
> on usb key two --> repo.win
> 
> Then, on repo.win, I'll do:
> # before daily work on windows
> fetch from repo.linux
> # after daily work on windows
> push to repo.linux
> 
> Otherwise, on repo.linux:
> # before nightly work on linux
> fetch from repo.windows
> # after nightly work on linux
> push to repo.windows
> 
> It's possible, or I need a third bare repository between windows and 
> linux ???

No need for a third one. You can even use alternates to save space:

$ git clone -l -s repo.linux repo.windows

When git-gc'ing, the objects will be packed, but if they are present in 
both repo.linux and repo.windows, the objects from repo.linux will be 
reused in repo.windows.

Note: USB sticks are almost as fragile as disks used to be... So, try 
avoiding writes if you can...

Ciao,
Dscho

Re: using the same repo with different OS

[Stefano Spinucci]

On 2/28/07, Shawn O. Pearce <spearce@spearce.org> wrote:
> Stefano Spinucci <virgo977virgo@gmail.com> wrote:
> > I noticed today that my notes about compiling Git on cygwin to work
> > with FAT32 (export NO_MMAP=1) on the Wiki page WindowsInstall were
> > removed.
>
> That was me.  NO_MMAP=1 is now the default on Cygwin.

Unfortunately, the Git cygwin mantainer decided to compile git without
the NO_MMAP option (see the announcement
http://cygwin.com/ml/cygwin-announce/2007-03/msg00005.html and a reply
to my message http://cygwin.com/ml/cygwin/2007-03/msg00567.html).

Then, I guess if on the Wiki page WindowsInstall we should add a note
about recompiling manually Git to work with FAT32.


PS

On the Git cygwin announcement, the mantainer Eric Blake said:
"However, it means that this version does assume that you are not
using FAT or FAT32 to
hold your repositories, since they *do not store file permissions very
accurately*."

What file permissions are not stored accurately ???

Shouldn't be added somewhere (maybe on the GitFaq) a note about Git on
FAT32 problems (if there are any) ???


bye

---
Stefano Spinucci