This is needed by processes (such as zabbix_agentd) that require read access to /proc directory. Sounds like some config option needs to be enabled in the grsec kernel.

(from redmine: issue id 490, created on 2010-12-07, closed on 2010-12-09)

• Changesets:
  • Revision b868fd50 on 2010-12-07T14:18:13Z:

main/linux-grsec: enable grsecurity proc usergroup

All users in group number 700 will be able to see all process info,
network related stuff and kernel symbols.

ref #490

• Revision a946e1cd on 2010-12-08T15:57:50Z:

main/linux-grsec: use GID=30 for readproc

http://lists.alpinelinux.org/alpine-devel/1214.html
ref #490

• Revision 91e51d6b on 2010-12-09T08:14:45Z:

main/linux-grsec: enable grsecurity proc usergroup

All users in group number 700 will be able to see all process info,
network related stuff and kernel symbols.

ref #490
(cherry picked from commit b868fd504bdc0d6abede6b4ca4892405d9810560)

• Revision 4bdbac4b on 2010-12-09T08:14:54Z:

main/linux-grsec: use GID=30 for readproc

http://lists.alpinelinux.org/alpine-devel/1214.html
ref #490
(cherry picked from commit a946e1cdc42ee7b7f804f46b818e029a2d7856cb)