Re: [fuse-devel] Do I need to support both - libfuse2 and libfuse3 in my application in order to work on more Linux distros, in case I deploy libfuse with my application

[Antonio SJ M. <tra...@sp...>]

The supported kernels are so old as to be almost pointless to continue 
supporting. I wouldn't worry about that unless you're deploying to 
seriously old / niche systems.

But yes... you should read about the init callback, "want" field, and 
FUSE_CAP values. Otherwise your filesystem could request something it 
doesn't get or get something it doesn't expect and behave incorrectly.

On 10/1/2019 8:58 AM, Cyril Cyrov wrote:
> Yes, I think I totally get your point.
>
> My point of view is - building libfuse3 on older systems is possible
> and it cost me like 2-3 hours to build the necessary tools. Packing
> fusermount3 in the installer also doesn't sound so hard - we already
> do deploy libfuse.so, that's just one ore file. And finally, patching
> in order to find the fusermount3 binary - this seems like a trivial
> patch.
> Also given the fact, that we rarely update fuse versions, this effort
> seems to worth it.
>
> My two concerns, that I still have, are:
> 1) is there any security risk in deploying fusermount3 and should I do
> anything special, except just copy the binary into the installer?
> 2) how will I understand that the kernel is too old for some feature,
> that I need (I get it, that it's during the FUSE_INIT phase, I'll have
> to read more about this).
>
> On Tue, Oct 1, 2019 at 3:19 PM Antonio SJ Musumeci <tra...@sp...> wrote:
>> You can optionally deploy it or patch the build to install to a
>> different location / filename.
>>
>> This is what I was getting at prior. The library is not designed to be
>> used this way so without upstreaming some changing that make it easier
>> to do so you'll have to maintain some part of the setup.
>>
>> My biggest problem with embedding libfuse3 was the build system simply
>> not working on older platforms and getting that replaced or officially
>> supporting multiple systems doesn't seem a reasonable ask.
>>
>> On 10/1/2019 7:31 AM, Cyril Cyrov wrote:
>>> Actually, deploying `libfuse3.so` won't be enough, deploying
>>> `fusermount3` is also necessary (+ building libfuse with `-D
>>> FUSERMOUNT_DIR=.....`)? Isn't this some kind of a security issue
>>> (deploying fusermount3)?
>>>
>>> On Tue, Oct 1, 2019 at 1:53 PM Cyril Cyrov <cyr...@gm...> wrote:
>>>> Hi,
>>>>
>>>> Here's an introduction for this thread:
>>>> https://github.com/libfuse/libfuse/issues/460
>>>>
>>>> Long story short:
>>>> Q: How can I support both libfuse2 and libfuse3 in order to make my
>>>> app work on more Linux distos?
>>>> A: You don't need to do that.
>>>>
>>>> So, continuing the discussion here.
>>>>
>>>> ---
>>>>
>>>> My misunderstanding comes from the fact, that I though there are two
>>>> different kernel modules for the two versions and that libfuse3 can
>>>> only work on Linux distros, which do have `fuse3` package installed
>>>> (and these distros are just a few). This misunderstanding was also
>>>> supported by the fact, that libfuse3 needs fusermount3 in order to
>>>> create a mountpoint.
>>>>
>>>> Another miscommunication occurred by the different interpretation of
>>>> "patching the fuse implementation" and "embedding" fuse.
>>>>
>>>> We do deploy a libfuse shared object with our application. So, this is
>>>> not an issue at all.
>>>>
>>>> My concern was - can I use and deploy libfuse3 on older Linux distros,
>>>> like CentOS 6, for example?
>>>>
>>>> What confuses me further is that I cannot find any matching between
>>>> libfuse versions and kernel versions, explaining which libfuse version
>>>> is compatible with which kernel versions.
>>>>
>>>> ---
>>>>
>>>> @trapexit
>>>>> Then you'll have to deal with the distro's support
>>>> By "avoid patching the fuse implementation" I didn't mean I don't want
>>>> to deploy fuse build, I just misunderstood you and thought that you
>>>> suggest actually making some source patch in order to "merge" them
>>>> somehow. Sorry for the misleading.
>>>>
>>>> ---
>>>>
>>>> @Nikratio:
>>>>> "Why don't you ship two binaries (one for libfuse2 and one for libfuse3) together with a small wrapper that picks with version to use?"
>>>> This will be necessary only if we don't deploy a build for libfuse, correct?
>>>>
>>>> ---
>>>>
>>>> So, I'll try to wrap things up, please correct me if I'm wrong - appreciated!
>>>>
>>>> We can actually use only libfuse3 and if we deploy it (or statically
>>>> link it in our application) this should work fine all Linux distros,
>>>> which otherwise would work fine with libfuse2. Is that correct?
>>>> Also, is there a way to find out which libfuse3 features depend on
>>>> which Linux kernel, in order to work fine?
>>>>
>>>> Thanks,
>>>> Kiril
>>
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