Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[Peter Kjellerstedt]

[ I am moving this discussion to the OE-core list as I believe 
  that is where it belongs. ]

> -----Original Message-----
> From: yocto-bounces@yoctoproject.org [mailto:yocto-
> bounces@yoctoproject.org] On Behalf Of Paul Eggleton
> Sent: den 2 december 2014 15:07
> To: Fabrice Coulon
> Cc: yocto@yoctoproject.org
> Subject: Re: [yocto] Export bitbake variables between recipes
> 
> Hi Fabrice,
> 
> On Tuesday 02 December 2014 14:07:40 Fabrice Coulon wrote:
> > Is it possible to export one bitbake variable from one recipe 
> > and make it available from inside another recipe? For example: 
> > we want to export from our systemd_%.bbappend where the 
> > systemctl command has been installed, in order to, from another 
> > recipe depending on systemd, refer to the absolute path where 
> > systemctl was installed. Any ideas or suggestions on how to do
> > that?
> 
> There's no mechanism to do this, no. The only way for this kind of
> thing to work is for it to be specified at the configuration level 
> (e.g. ${bindir} points to the subdirectory /usr/bin and this variable 
> would be used both when choosing where the executable should be 
> installed and finding it later - this would typically be how this 
> kind of problem would be solved since it would be unusual to have 
> systemctl installed somewhere other than ${bindir}).

Actually, since the systemd recipe in Poky is configured in an 
extremely weird way (using --with-rootprefix=${base_prefix} and 
--with-rootlib=${base_libdir}), systemctl actually ends up in 
${base_bindir} rather than ${bindir}. And this is the whole reason 
for our troubles since everything else we had prior to switching 
to Poky expected systemd to be installed in /usr...

Can anyone please explain why OE-core installs systemd to / rather 
than /usr? Because I have traced the recipe all the way back to its 
introduction in OE classic, and I cannot find any rationale for 
this odd decision. And it is extra weird given the systemd authors' 
agenda that everything should be in /usr (and /etc)...

> (Another alternative is pkg-config, but I don't think that really
> applies in this situation.)

Nope.

> Cheers,
> Paul
> 
> --
> 
> Paul Eggleton
> Intel Open Source Technology Centre

//Peter

Re: Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[Mark Hatle]

On 12/2/14, 12:27 PM, Peter Kjellerstedt wrote:
> [ I am moving this discussion to the OE-core list as I believe
>    that is where it belongs. ]
>
>> -----Original Message-----
>> From: yocto-bounces@yoctoproject.org [mailto:yocto-
>> bounces@yoctoproject.org] On Behalf Of Paul Eggleton
>> Sent: den 2 december 2014 15:07
>> To: Fabrice Coulon
>> Cc: yocto@yoctoproject.org
>> Subject: Re: [yocto] Export bitbake variables between recipes
>>
>> Hi Fabrice,
>>
>> On Tuesday 02 December 2014 14:07:40 Fabrice Coulon wrote:
>>> Is it possible to export one bitbake variable from one recipe
>>> and make it available from inside another recipe? For example:
>>> we want to export from our systemd_%.bbappend where the
>>> systemctl command has been installed, in order to, from another
>>> recipe depending on systemd, refer to the absolute path where
>>> systemctl was installed. Any ideas or suggestions on how to do
>>> that?
>>
>> There's no mechanism to do this, no. The only way for this kind of
>> thing to work is for it to be specified at the configuration level
>> (e.g. ${bindir} points to the subdirectory /usr/bin and this variable
>> would be used both when choosing where the executable should be
>> installed and finding it later - this would typically be how this
>> kind of problem would be solved since it would be unusual to have
>> systemctl installed somewhere other than ${bindir}).
>
> Actually, since the systemd recipe in Poky is configured in an
> extremely weird way (using --with-rootprefix=${base_prefix} and
> --with-rootlib=${base_libdir}), systemctl actually ends up in
> ${base_bindir} rather than ${bindir}. And this is the whole reason
> for our troubles since everything else we had prior to switching
> to Poky expected systemd to be installed in /usr...

Because we support the split between / and /usr for embedded systems with 
multiple partitions/disks.

If you set it to /usr, then technically you are violating the FHS, as you now 
require /usr in order to boot the system.

What programs are expecting these things in a specific path?  Why aren't they 
either using the PATH, or using a similar configuration mechanism via the recipes?

> Can anyone please explain why OE-core installs systemd to / rather
> than /usr? Because I have traced the recipe all the way back to its
> introduction in OE classic, and I cannot find any rationale for
> this odd decision. And it is extra weird given the systemd authors'
> agenda that everything should be in /usr (and /etc)...

It's only strange compared to Fedora.  We're not Fedora.. and I've got systems 
that need to boot from a small '/' before mounting '/usr'.

(In prior discussions we've made the decision to not fix every library or 
application, but there is a warning you can enable that will show you what 
libraries and applications live in '/' but have obvious linkage to '/usr'.)

>> (Another alternative is pkg-config, but I don't think that really
>> applies in this situation.)
>
> Nope.
>
>> Cheers,
>> Paul
>>
>> --
>>
>> Paul Eggleton
>> Intel Open Source Technology Centre
>
> //Peter
>
>

Re: Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[Peter Kjellerstedt]

> -----Original Message-----
> From: openembedded-core-bounces@lists.openembedded.org
> [mailto:openembedded-core-bounces@lists.openembedded.org] On Behalf Of
> Mark Hatle
> Sent: den 2 december 2014 19:45
> To: openembedded-core@lists.openembedded.org
> Subject: Re: [OE-core] Why is systemd installed to / (was: [yocto]
> Export bitbake variables between recipes)
> 
> On 12/2/14, 12:27 PM, Peter Kjellerstedt wrote:
> > [ I am moving this discussion to the OE-core list as I believe
> >    that is where it belongs. ]
> >
> >> -----Original Message-----
> >> From: yocto-bounces@yoctoproject.org [mailto:yocto-
> >> bounces@yoctoproject.org] On Behalf Of Paul Eggleton
> >> Sent: den 2 december 2014 15:07
> >> To: Fabrice Coulon
> >> Cc: yocto@yoctoproject.org
> >> Subject: Re: [yocto] Export bitbake variables between recipes
> >>
> >> Hi Fabrice,
> >>
> >> On Tuesday 02 December 2014 14:07:40 Fabrice Coulon wrote:
> >>> Is it possible to export one bitbake variable from one recipe
> >>> and make it available from inside another recipe? For example:
> >>> we want to export from our systemd_%.bbappend where the
> >>> systemctl command has been installed, in order to, from another
> >>> recipe depending on systemd, refer to the absolute path where
> >>> systemctl was installed. Any ideas or suggestions on how to do
> >>> that?
> >>
> >> There's no mechanism to do this, no. The only way for this kind of
> >> thing to work is for it to be specified at the configuration level
> >> (e.g. ${bindir} points to the subdirectory /usr/bin and this variable
> >> would be used both when choosing where the executable should be
> >> installed and finding it later - this would typically be how this
> >> kind of problem would be solved since it would be unusual to have
> >> systemctl installed somewhere other than ${bindir}).
> >
> > Actually, since the systemd recipe in Poky is configured in an
> > extremely weird way (using --with-rootprefix=${base_prefix} and
> > --with-rootlib=${base_libdir}), systemctl actually ends up in
> > ${base_bindir} rather than ${bindir}. And this is the whole reason
> > for our troubles since everything else we had prior to switching
> > to Poky expected systemd to be installed in /usr...
> 
> Because we support the split between / and /usr for embedded systems
> with multiple partitions/disks.

Hmm, ok.

> If you set it to /usr, then technically you are violating the FHS, as
> you now require /usr in order to boot the system.

Ok. We have never split / and /usr in our products so that thought 
did not occur to me.

> What programs are expecting these things in a specific path?  Why
> aren't they either using the PATH, or using a similar configuration 
> mechanism via the recipes?

In the specific case it was a systemd unit file that wants to do 
ExecStartPost=/usr/bin/systemctl kill --signal HUP rsyslog.service
and since paths in unit files must be absolute this caused problems 
for us when building with Poky since then systemctl is in /bin, but 
when building with our old build system it is in /usr/bin...

Now it is no major problem to fix the specific unit file, because we 
can just do ExecStartPost=/bin/sh -c "systemctl kill ...", but the 
difference between our two build systems has caused us quite a lot  
of extra work.

> > Can anyone please explain why OE-core installs systemd to / rather
> > than /usr? Because I have traced the recipe all the way back to its
> > introduction in OE classic, and I cannot find any rationale for
> > this odd decision. And it is extra weird given the systemd authors'
> > agenda that everything should be in /usr (and /etc)...
> 
> It's only strange compared to Fedora.  We're not Fedora.. and I've 
> got systems that need to boot from a small '/' before mounting '/usr'.

Speaking of Fedora, would an official image feature, e.g., "unified-fs", 
be acceptable for OE-Core that sets up the file system with /bin, /sbin 
and /lib* as links to their /usr counterparts? That would alleviate our 
problems with the differences in how systemd is installed.

> (In prior discussions we've made the decision to not fix every library
> or application, but there is a warning you can enable that will show 
> you what libraries and applications live in '/' but have obvious 
> linkage to '/usr'.)
> 
> >> (Another alternative is pkg-config, but I don't think that really
> >> applies in this situation.)
> >
> > Nope.
> >
> >> Cheers,
> >> Paul
> >>
> >> --
> >>
> >> Paul Eggleton
> >> Intel Open Source Technology Centre
> >
> > //Peter

//Peter

Re: Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[Mark Hatle]

On 12/3/14, 9:36 AM, Peter Kjellerstedt wrote:
>>> Can anyone please explain why OE-core installs systemd to / rather
>>> than /usr? Because I have traced the recipe all the way back to its
>>> introduction in OE classic, and I cannot find any rationale for
>>> this odd decision. And it is extra weird given the systemd authors'
>>> agenda that everything should be in /usr (and /etc)...
>>
>> It's only strange compared to Fedora.  We're not Fedora.. and I've
>> got systems that need to boot from a small '/' before mounting '/usr'.
>
> Speaking of Fedora, would an official image feature, e.g., "unified-fs",
> be acceptable for OE-Core that sets up the file system with /bin, /sbin
> and /lib* as links to their /usr counterparts? That would alleviate our
> problems with the differences in how systemd is installed.

The system permits developers to set the paths for the various pieces.  To get a 
Fedora like unified filesystem, you could do something like:

* provide your own fs-perms.txt:

/usr/bin	link	${base_bindir}
/usr/sbin	link	${base_sbindir}
/usr/lib	link	${base_libdir}

Then in your local.conf:

bindir = "${base_bindir}"
sbindir = "${base_sbindir}"
libdir = "${base_libdir}"


This will result in /usr/bin, sbin and lib being linked to /bin, /sbin, /lib -- 
and all of the package produced for your configuration will only reference '/'.

This isn't that unusual of a configuration from what I've been told.

--Mark

>> (In prior discussions we've made the decision to not fix every library
>> or application, but there is a warning you can enable that will show
>> you what libraries and applications live in '/' but have obvious
>> linkage to '/usr'.)
>>
>>>> (Another alternative is pkg-config, but I don't think that really
>>>> applies in this situation.)
>>>
>>> Nope.
>>>
>>>> Cheers,
>>>> Paul
>>>>
>>>> --
>>>>
>>>> Paul Eggleton
>>>> Intel Open Source Technology Centre
>>>
>>> //Peter
>
> //Peter
>

Re: Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[Peter Kjellerstedt]

> -----Original Message-----
> From: openembedded-core-bounces@lists.openembedded.org
> [mailto:openembedded-core-bounces@lists.openembedded.org] On Behalf Of
> Mark Hatle
> Sent: den 3 december 2014 16:47
> To: Peter Kjellerstedt; openembedded-core@lists.openembedded.org
> Subject: Re: [OE-core] Why is systemd installed to / (was: [yocto]
> Export bitbake variables between recipes)
> 
> On 12/3/14, 9:36 AM, Peter Kjellerstedt wrote:
> >>> Can anyone please explain why OE-core installs systemd to / 
> >>> rather than /usr? Because I have traced the recipe all the 
> >>> way back to its introduction in OE classic, and I cannot 
> >>> find any rationale for this odd decision. And it is extra 
> >>> weird given the systemd authors' agenda that everything 
> >>> should be in /usr (and /etc)...
> >>
> >> It's only strange compared to Fedora.  We're not Fedora.. and 
> >> I've got systems that need to boot from a small '/' before 
> >> mounting '/usr'.
> >
> > Speaking of Fedora, would an official image feature, e.g., 
> > "unified-fs", be acceptable for OE-Core that sets up the file 
> > system with /bin, /sbin and /lib* as links to their /usr 
> > counterparts? That would alleviate our problems with the 
> > differences in how systemd is installed.
> 
> The system permits developers to set the paths for the various pieces.
> To get a Fedora like unified filesystem, you could do something like:
> 
> * provide your own fs-perms.txt:

I had not noticed fs-perms.txt before. And it seems easy enough 
to extend via the FILESYSTEMS_PERMS_TABLES variable. :)

> /usr/bin	link	${base_bindir}
> /usr/sbin	link	${base_sbindir}
> /usr/lib	link	${base_libdir}
> 
> Then in your local.conf:
> 
> bindir = "${base_bindir}"
> sbindir = "${base_sbindir}"
> libdir = "${base_libdir}"

I think you mean the opposite, i.e., that /bin should be a 
link to ${bindir} and ${base_bindir} should be set to ${bindir}, 
but I get your point.

> This will result in /usr/bin, sbin and lib being linked to /bin, 
> /sbin, /lib -- and all of the package produced for your 
> configuration will only reference '/'.
> 
> This isn't that unusual of a configuration from what I've been told.

Which is why I think it warrants an official distro feature (an 
image feature, as I originally suggested, will of course not do 
if it is done the way you suggest since the packages' contents 
are modified). That way people would not have to invent the wheel 
over and over again (and somehow find out that there is such a 
thing as fs-perms.txt which up until now had eluded me).

> --Mark

//Peter

Re: Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[ChenQi]

On 12/04/2014 09:34 PM, Peter Kjellerstedt wrote:
>> -----Original Message-----
>> From: openembedded-core-bounces@lists.openembedded.org
>> [mailto:openembedded-core-bounces@lists.openembedded.org] On Behalf Of
>> Mark Hatle
>> Sent: den 3 december 2014 16:47
>> To: Peter Kjellerstedt; openembedded-core@lists.openembedded.org
>> Subject: Re: [OE-core] Why is systemd installed to / (was: [yocto]
>> Export bitbake variables between recipes)
>>
>> On 12/3/14, 9:36 AM, Peter Kjellerstedt wrote:
>>>>> Can anyone please explain why OE-core installs systemd to /
>>>>> rather than /usr? Because I have traced the recipe all the
>>>>> way back to its introduction in OE classic, and I cannot
>>>>> find any rationale for this odd decision. And it is extra
>>>>> weird given the systemd authors' agenda that everything
>>>>> should be in /usr (and /etc)...
>>>> It's only strange compared to Fedora.  We're not Fedora.. and
>>>> I've got systems that need to boot from a small '/' before
>>>> mounting '/usr'.
>>> Speaking of Fedora, would an official image feature, e.g.,
>>> "unified-fs", be acceptable for OE-Core that sets up the file
>>> system with /bin, /sbin and /lib* as links to their /usr
>>> counterparts? That would alleviate our problems with the
>>> differences in how systemd is installed.
>> The system permits developers to set the paths for the various pieces.
>> To get a Fedora like unified filesystem, you could do something like:
>>
>> * provide your own fs-perms.txt:
> I had not noticed fs-perms.txt before. And it seems easy enough
> to extend via the FILESYSTEMS_PERMS_TABLES variable. :)
>
>> /usr/bin	link	${base_bindir}
>> /usr/sbin	link	${base_sbindir}
>> /usr/lib	link	${base_libdir}
>>
>> Then in your local.conf:
>>
>> bindir = "${base_bindir}"
>> sbindir = "${base_sbindir}"
>> libdir = "${base_libdir}"
> I think you mean the opposite, i.e., that /bin should be a
> link to ${bindir} and ${base_bindir} should be set to ${bindir},
> but I get your point.
>
>> This will result in /usr/bin, sbin and lib being linked to /bin,
>> /sbin, /lib -- and all of the package produced for your
>> configuration will only reference '/'.
>>
>> This isn't that unusual of a configuration from what I've been told.
> Which is why I think it warrants an official distro feature (an
> image feature, as I originally suggested, will of course not do
> if it is done the way you suggest since the packages' contents
> are modified). That way people would not have to invent the wheel
> over and over again (and somehow find out that there is such a
> thing as fs-perms.txt which up until now had eluded me).
>
>> --Mark
> //Peter
>

Hi Peter,

It's easy to link /usr/bin to /bin, /usr/sbin to /sbin and make things 
work in OE.
But if we want the opposite to work, we might need several additional 
patches to OE.

Several days ago, I tried to do /usr merge in OE (like what Fedora and 
Arch does). It turned out that we need to patch several packages to make 
things work.

(I haven't sent out the patches because it's just some initial 
investigation and I'm not sure if people want this feature or not.)

If you want this feature in OE, please open a bug/enhancement in 
bugzilla https://bugzilla.yoctoproject.org/ to see if the community 
wants it or not.

Regards,
Chen Qi

Re: Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[Mark Hatle]

On 12/4/14, 9:00 PM, ChenQi wrote:
> On 12/04/2014 09:34 PM, Peter Kjellerstedt wrote:
>>> -----Original Message-----
>>> From: openembedded-core-bounces@lists.openembedded.org
>>> [mailto:openembedded-core-bounces@lists.openembedded.org] On Behalf Of
>>> Mark Hatle
>>> Sent: den 3 december 2014 16:47
>>> To: Peter Kjellerstedt; openembedded-core@lists.openembedded.org
>>> Subject: Re: [OE-core] Why is systemd installed to / (was: [yocto]
>>> Export bitbake variables between recipes)
>>>
>>> On 12/3/14, 9:36 AM, Peter Kjellerstedt wrote:
>>>>>> Can anyone please explain why OE-core installs systemd to /
>>>>>> rather than /usr? Because I have traced the recipe all the
>>>>>> way back to its introduction in OE classic, and I cannot
>>>>>> find any rationale for this odd decision. And it is extra
>>>>>> weird given the systemd authors' agenda that everything
>>>>>> should be in /usr (and /etc)...
>>>>> It's only strange compared to Fedora.  We're not Fedora.. and
>>>>> I've got systems that need to boot from a small '/' before
>>>>> mounting '/usr'.
>>>> Speaking of Fedora, would an official image feature, e.g.,
>>>> "unified-fs", be acceptable for OE-Core that sets up the file
>>>> system with /bin, /sbin and /lib* as links to their /usr
>>>> counterparts? That would alleviate our problems with the
>>>> differences in how systemd is installed.
>>> The system permits developers to set the paths for the various pieces.
>>> To get a Fedora like unified filesystem, you could do something like:
>>>
>>> * provide your own fs-perms.txt:
>> I had not noticed fs-perms.txt before. And it seems easy enough
>> to extend via the FILESYSTEMS_PERMS_TABLES variable. :)
>>
>>> /usr/bin	link	${base_bindir}
>>> /usr/sbin	link	${base_sbindir}
>>> /usr/lib	link	${base_libdir}
>>>
>>> Then in your local.conf:
>>>
>>> bindir = "${base_bindir}"
>>> sbindir = "${base_sbindir}"
>>> libdir = "${base_libdir}"
>> I think you mean the opposite, i.e., that /bin should be a
>> link to ${bindir} and ${base_bindir} should be set to ${bindir},
>> but I get your point.
>>
>>> This will result in /usr/bin, sbin and lib being linked to /bin,
>>> /sbin, /lib -- and all of the package produced for your
>>> configuration will only reference '/'.
>>>
>>> This isn't that unusual of a configuration from what I've been told.
>> Which is why I think it warrants an official distro feature (an
>> image feature, as I originally suggested, will of course not do
>> if it is done the way you suggest since the packages' contents
>> are modified). That way people would not have to invent the wheel
>> over and over again (and somehow find out that there is such a
>> thing as fs-perms.txt which up until now had eluded me).
>>
>>> --Mark
>> //Peter
>>
>
> Hi Peter,
>
> It's easy to link /usr/bin to /bin, /usr/sbin to /sbin and make things
> work in OE.
> But if we want the opposite to work, we might need several additional
> patches to OE.

Exactly.. and going back to the FHS, the FHS says that '/' is required to boot, 
/usr is not.  So /usr should be linked to / for those items.

There is a fairly standard OE configuration some people do where they don't 
define a /usr at all.  They just set the prefix (normally /usr) to '/'.

That SHOULD be working still, at least it used to be a well tested configuration...

> Several days ago, I tried to do /usr merge in OE (like what Fedora and
> Arch does). It turned out that we need to patch several packages to make
> things work.
>
> (I haven't sent out the patches because it's just some initial
> investigation and I'm not sure if people want this feature or not.)
>
> If you want this feature in OE, please open a bug/enhancement in
> bugzilla https://bugzilla.yoctoproject.org/ to see if the community
> wants it or not.
>
> Regards,
> Chen Qi
>
>

Re: Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[Adrian Freihofer]

[-- Attachment #1: Type: text/plain, Size: 4944 bytes --]

On Thursday 04 December 2014 21.46:50 Mark Hatle wrote:
> On 12/4/14, 9:00 PM, ChenQi wrote:
> > On 12/04/2014 09:34 PM, Peter Kjellerstedt wrote:
> >>> -----Original Message-----
> >>> From: openembedded-core-bounces@lists.openembedded.org
> >>> [mailto:openembedded-core-bounces@lists.openembedded.org] On Behalf Of
> >>> Mark Hatle
> >>> Sent: den 3 december 2014 16:47
> >>> To: Peter Kjellerstedt; openembedded-core@lists.openembedded.org
> >>> Subject: Re: [OE-core] Why is systemd installed to / (was: [yocto]
> >>> Export bitbake variables between recipes)
> >>>
> >>> On 12/3/14, 9:36 AM, Peter Kjellerstedt wrote:
> >>>>>> Can anyone please explain why OE-core installs systemd to /
> >>>>>> rather than /usr? Because I have traced the recipe all the
> >>>>>> way back to its introduction in OE classic, and I cannot
> >>>>>> find any rationale for this odd decision. And it is extra
> >>>>>> weird given the systemd authors' agenda that everything
> >>>>>> should be in /usr (and /etc)...
> >>>>> It's only strange compared to Fedora.  We're not Fedora.. and
> >>>>> I've got systems that need to boot from a small '/' before
> >>>>> mounting '/usr'.
> >>>> Speaking of Fedora, would an official image feature, e.g.,
> >>>> "unified-fs", be acceptable for OE-Core that sets up the file
> >>>> system with /bin, /sbin and /lib* as links to their /usr
> >>>> counterparts? That would alleviate our problems with the
> >>>> differences in how systemd is installed.
> >>> The system permits developers to set the paths for the various pieces.
> >>> To get a Fedora like unified filesystem, you could do something like:
> >>>
> >>> * provide your own fs-perms.txt:
> >> I had not noticed fs-perms.txt before. And it seems easy enough
> >> to extend via the FILESYSTEMS_PERMS_TABLES variable. :)
> >>
> >>> /usr/bin	link	${base_bindir}
> >>> /usr/sbin	link	${base_sbindir}
> >>> /usr/lib	link	${base_libdir}
> >>>
> >>> Then in your local.conf:
> >>>
> >>> bindir = "${base_bindir}"
> >>> sbindir = "${base_sbindir}"
> >>> libdir = "${base_libdir}"
> >> I think you mean the opposite, i.e., that /bin should be a
> >> link to ${bindir} and ${base_bindir} should be set to ${bindir},
> >> but I get your point.
> >>
> >>> This will result in /usr/bin, sbin and lib being linked to /bin,
> >>> /sbin, /lib -- and all of the package produced for your
> >>> configuration will only reference '/'.
> >>>
> >>> This isn't that unusual of a configuration from what I've been told.
> >> Which is why I think it warrants an official distro feature (an
> >> image feature, as I originally suggested, will of course not do
> >> if it is done the way you suggest since the packages' contents
> >> are modified). That way people would not have to invent the wheel
> >> over and over again (and somehow find out that there is such a
> >> thing as fs-perms.txt which up until now had eluded me).
> >>
> >>> --Mark
> >> //Peter
> >>
> >
> > Hi Peter,
> >
> > It's easy to link /usr/bin to /bin, /usr/sbin to /sbin and make things
> > work in OE.
> > But if we want the opposite to work, we might need several additional
> > patches to OE.
> 
> Exactly.. and going back to the FHS, the FHS says that '/' is required to boot, 
> /usr is not.  So /usr should be linked to / for those items.
> 
> There is a fairly standard OE configuration some people do where they don't 
> define a /usr at all.  They just set the prefix (normally /usr) to '/'.
> 
> That SHOULD be working still, at least it used to be a well tested configuration...
> 
> > Several days ago, I tried to do /usr merge in OE (like what Fedora and
> > Arch does). It turned out that we need to patch several packages to make
> > things work.
> >
> > (I haven't sent out the patches because it's just some initial
> > investigation and I'm not sure if people want this feature or not.)
> >
> > If you want this feature in OE, please open a bug/enhancement in
> > bugzilla https://bugzilla.yoctoproject.org/ to see if the community
> > wants it or not.
> >
> > Regards,
> > Chen Qi
> >
> >
> 
> 
Hi Mark

Lennard Poettering and others have good arguments to have no /bin, /lib and /sbin folder at all. There is an interesting blog here: http://0pointer.net/blog/revisiting-how-we-put-together-linux-systems.html[1]. In short: The goal is to have one mount point (/usr) where all the read only binaries are in. Having /usr on a read only btrfs partition would allow to use the send receive feature (binary diff on filesystem level) of btrfs to deploy software updates to many devices. This approach could provide a generic, robust and optimized SW update procedure for embedded systems as well.

Regards,
Adrian



--------------------
Adrian Freihofer
Gschwaderweg 29
8610 Uster
043 497 84 01

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[1] http://0pointer.net/blog/revisiting-how-we-put-together-linux-systems.html

[-- Attachment #2: Type: text/html, Size: 21409 bytes --]

Re: Why is systemd installed to / (was: [yocto] Export bitbake variables between recipes)

[Peter Kjellerstedt]

> -----Original Message-----
> From: openembedded-core-bounces@lists.openembedded.org
> [mailto:openembedded-core-bounces@lists.openembedded.org] On Behalf Of
> ChenQi
> Sent: den 5 december 2014 04:01
> To: openembedded-core@lists.openembedded.org
> Subject: Re: [OE-core] Why is systemd installed to / (was: [yocto]
> Export bitbake variables between recipes)
> 
> On 12/04/2014 09:34 PM, Peter Kjellerstedt wrote:
> >> -----Original Message-----
> >> From: openembedded-core-bounces@lists.openembedded.org
> >> [mailto:openembedded-core-bounces@lists.openembedded.org] On Behalf
> Of
> >> Mark Hatle
> >> Sent: den 3 december 2014 16:47
> >> To: Peter Kjellerstedt; openembedded-core@lists.openembedded.org
> >> Subject: Re: [OE-core] Why is systemd installed to / (was: [yocto]
> >> Export bitbake variables between recipes)
> >>
> >> On 12/3/14, 9:36 AM, Peter Kjellerstedt wrote:
> >>>>> Can anyone please explain why OE-core installs systemd to /
> >>>>> rather than /usr? Because I have traced the recipe all the
> >>>>> way back to its introduction in OE classic, and I cannot
> >>>>> find any rationale for this odd decision. And it is extra
> >>>>> weird given the systemd authors' agenda that everything
> >>>>> should be in /usr (and /etc)...
> >>>> It's only strange compared to Fedora.  We're not Fedora.. and
> >>>> I've got systems that need to boot from a small '/' before
> >>>> mounting '/usr'.
> >>> Speaking of Fedora, would an official image feature, e.g.,
> >>> "unified-fs", be acceptable for OE-Core that sets up the file
> >>> system with /bin, /sbin and /lib* as links to their /usr
> >>> counterparts? That would alleviate our problems with the
> >>> differences in how systemd is installed.
> >> The system permits developers to set the paths for the various
> pieces.
> >> To get a Fedora like unified filesystem, you could do something like:
> >>
> >> * provide your own fs-perms.txt:
> > I had not noticed fs-perms.txt before. And it seems easy enough
> > to extend via the FILESYSTEMS_PERMS_TABLES variable. :)
> >
> >> /usr/bin	link	${base_bindir}
> >> /usr/sbin	link	${base_sbindir}
> >> /usr/lib	link	${base_libdir}
> >>
> >> Then in your local.conf:
> >>
> >> bindir = "${base_bindir}"
> >> sbindir = "${base_sbindir}"
> >> libdir = "${base_libdir}"
> > I think you mean the opposite, i.e., that /bin should be a
> > link to ${bindir} and ${base_bindir} should be set to ${bindir},
> > but I get your point.
> >
> >> This will result in /usr/bin, sbin and lib being linked to /bin,
> >> /sbin, /lib -- and all of the package produced for your
> >> configuration will only reference '/'.
> >>
> >> This isn't that unusual of a configuration from what I've been told.
> > Which is why I think it warrants an official distro feature (an
> > image feature, as I originally suggested, will of course not do
> > if it is done the way you suggest since the packages' contents
> > are modified). That way people would not have to invent the wheel
> > over and over again (and somehow find out that there is such a
> > thing as fs-perms.txt which up until now had eluded me).
> >
> >> --Mark
> > //Peter
> >
> 
> Hi Peter,
> 
> It's easy to link /usr/bin to /bin, /usr/sbin to /sbin and make things
> work in OE.
> But if we want the opposite to work, we might need several additional
> patches to OE.
> 
> Several days ago, I tried to do /usr merge in OE (like what Fedora and
> Arch does). It turned out that we need to patch several packages to
> make things work.
> 
> (I haven't sent out the patches because it's just some initial
> investigation and I'm not sure if people want this feature or not.)
> 
> If you want this feature in OE, please open a bug/enhancement in
> bugzilla https://bugzilla.yoctoproject.org/ to see if the community
> wants it or not.
> 
> Regards,
> Chen Qi

I have created a ticket for this now: 
https://bugzilla.yoctoproject.org/show_bug.cgi?id=7040

//Peter