Bug#324900: nscd: umount /var fails (unclean shutdowns)

[GOTO Masanori <gotom@debian.or.jp>]

At Thu, 25 Aug 2005 17:57:00 -0400,
Daniel Jacobowitz wrote:
> On Thu, Aug 25, 2005 at 05:53:05PM +0200, Zlatko Calusic wrote:
> > GOTO Masanori <gotom@debian.or.jp> writes:
> > 
> > > At Thu, 25 Aug 2005 12:56:04 +0200,
> > > Zlatko Calusic wrote:
> > >> rc        1119 root  mem       REG    8,9  217016   228931 /var/db/nscd/passwd
> 
> Note, this is a long-running bash.  Not many people use file-rc (that's
> what this is, right?)

It explains why most people don't see this issue.  Why does file-rc
cause problems?

> Does glibc open the nscd cache files directly rather than communicating
> with it via a socket?  Or does it communicate via shared memory?

Quick look at the source, mmap is used to share database file with
mmap MAP_SHARED, so the main communication should be done via a
socket.

> > rc    827 root  mem       REG    8,9  217016   228931 /var/db/nscd/passwd
> 
> [Is /var/db even FHS?]

FHS states as follows.

       5.5.2  /var/lib/misc : Miscellaneous variable data

       This directory contains variable data not placed in a subdirectory in
       /var/lib.  An attempt should be made to use relatively unique names in
       this directory to avoid namespace conflicts.

       Note that this hierarchy should contain files stored in /var/db in
       current BSD releases.  These include locate.database and mountdtab, and
       the kernel symbol database(s).

LDAP or DB data sometimes puts their db files on /var/lib/misc (I
think "misc" is vague term, though).  Actually
debian/patches/fhs-linux-paths.dpatch contains the following changes:

	--- glibc-2.1.1/sysdeps/unix/sysv/linux/paths.h~        Thu May 27 13:16:33 1999
	+++ glibc-2.1.1/sysdeps/unix/sysv/linux/paths.h Thu May 27 13:17:55 1999
	@@ -71,7 +71,7 @@
	 /* Provide trailing slash, since mostly used for building pathnames. */
	 #define        _PATH_DEV       "/dev/"
	 #define        _PATH_TMP       "/tmp/"
	-#define        _PATH_VARDB     "/var/db/"
	+#define        _PATH_VARDB     "/var/lib/misc/"

Another chioce is to use /var/cache - it's for application specific
caching data.  But currently I use /var/db instead of /var/lib/misc -
I have wondered this change is widely accepted.  I would like to hear
from all you guys about this placement.

Regards,
-- gotom