Usage of /var/db

[Christian Krause]

Hello,

During a review the following question came up:

Would it be OK if a package creates
/var/db/<pkgname>
for various kind of reasons (in this case a daemon would serve audio
files the user puts there)?

In Fedora only the nscd uses this directory:
/var/db/Makefile
/var/db/nscd/*

The FHS doesn't contain any specific guidelines about the usage of
/var/db/ and a quick web search revealed that on a couple of systems
some daemons use /var/db like this
/var/db/mysql
/var/db/openldap
etc.

1. Would it be acceptable in Fedora as well that a package creates
/var/db/<pkgname> ?

2. Would it make sense in this specific case, where a streaming server
would serve the audio files from this directory (per default)?
Personally I think that a collection of audio files should not be
considered a database and so it shouldn't be there. Since usually the
user has his audio collection in his home directory, I would just
configure the daemon that way, that the user has to specifically
configure the directory where the files reside the server should stream...

Thanks & Best regards,
Christian

[Nicolas Mailhot]

Le Jeu 28 janvier 2010 11:49, Christian Krause a écrit :
> Would it be OK if a package creates
> /var/db/<pkgname>
> for various kind of reasons (in this case a daemon would serve audio
> files the user puts there)?
>
> In Fedora only the nscd uses this directory:
> /var/db/Makefile
> /var/db/nscd/*
>
> The FHS doesn't contain any specific guidelines about the usage of
> /var/db/

On the contrary the FHS is very clear about such cases

« Applications must generally not add directories to the top level of /var.
Such directories should only be added if they have some system-wide
implication, and in consultation with the FHS mailing list. »

If it's not defined by the FHS, it should not be used or created.

[Ralf Corsepius]

On 01/28/2010 11:49 AM, Christian Krause wrote:
> Hello,
>
> During a review the following question came up:
>
> Would it be OK if a package creates
> /var/db/<pkgname>
> for various kind of reasons (in this case a daemon would serve audio
> files the user puts there)?

Generally speaking: No.
> In Fedora only the nscd uses this directory:
> /var/db/Makefile
> /var/db/nscd/*

Well, a fact which I consider similarly arguable as your case ;)

I am not sufficiently familiar with nscd, but I guess it using /var/db 
is a historic artifact, similar to /var/named, /var/ftp, /var/yp etc.
> The FHS doesn't contain any specific guidelines about the usage of
> /var/db/ and a quick web search revealed that on a couple of systems
> some daemons use /var/db like this
> /var/db/mysql
> /var/db/openldap
> etc.

To my knowledge this doesn't apply to fedora, because we generally 
advise people to use /var/lib/<package>
> Would it be acceptable in Fedora as well that a package creates
>
> /var/db/<pkgname>  ?

I would vote against it and would recommend /var/lib/<package> or a 
subdirectory thereof.

This way a package can "play whatever games", inside of this directory, 
if it needs to.
> Would it make sense in this specific case, where a streaming server
>
> would serve the audio files from this directory (per default)?

What kind of files are inside of this "db" directory?

Are they
* an arbitrary directory hierarchy of plain "content" files?
* a prestructured directory hierarchy (prestructured to meet the demands 
of your application) of plain "content" files?
* real "database" files (e.g. indicies on something else)?

Depending on the answers to these questions, there would be several 
alternatives, rsp. further questions to be discussed.
> Personally I think that a collection of audio files should not be
> considered a database and so it shouldn't be there.

c.f. my last comment.
> Since usually the
> user has his audio collection in his home directory,

Not in real deamon driven scenario. There he would have his audio 
collection in an arbitrary directory, (could be a decicated user's home, 
could be some directory below /srv, could be elsewhere).
> I would just
> configure the daemon that way, that the user has to specifically
> configure the directory where the files reside the server should stream...

Agreed, that's how I would do it.

Ralf

[Christian Krause]

On 01/28/2010 12:32 PM, Ralf Corsepius wrote:
> On 01/28/2010 11:49 AM, Christian Krause wrote:
> > Would it be acceptable in Fedora as well that a package creates
> >
> > /var/db/<pkgname>  ?
>
> I would vote against it and would recommend /var/lib/<package> or a
> subdirectory thereof.
>
> This way a package can "play whatever games", inside of this directory,
> if it needs to.

Ok, I fully agree that for other packages, which store their own
variable data, this would be the best solution.
> > Would it make sense in this specific case, where a streaming server
> >
> > would serve the audio files from this directory (per default)?
>
> What kind of files are inside of this "db" directory?
>
> Are they
> an arbitrary directory hierarchy of plain "content" files?

Yes, basically these will be the collection of audio/mp3 files the user
wants to be served.
> a prestructured directory hierarchy (prestructured to meet the demands
>
> of your application) of plain "content" files?
> real "database" files (e.g. indicies on something else)?

No.
> > Since usually the
> > user has his audio collection in his home directory,
>
> Not in real deamon driven scenario. There he would have his audio
> collection in an arbitrary directory, (could be a decicated user's home,
> could be some directory below /srv, could be elsewhere).

Yeah, agreed. We cannot predict which directory the user will use at all.
> > I would just
> > configure the daemon that way, that the user has to specifically
> > configure the directory where the files reside the server should
> > stream...
>
> Agreed, that's how I would do it.

Ok, we'll go this way.

Thanks for the clarification.

Best regards,
Christian