https://fedoraproject.org/wiki/Changes/RemoveNSCD

== Summary == This proposal intends to replace the ''nscd'' cache for named services with ''systemd-resolved'' for the `hosts` database and the ''sssd'' daemon for everything else.

== Owner == * Name: [[User:submachine| Arjun Shankar]] * Email: arjun@redhat.com

== Detailed Description ==

''nscd'' is a daemon that provides caching for accesses of the `passwd`, `group`, `hosts`, `services`, and `netgroup` databases through standard libc interfaces (such as `getpwnam`, `getpwuid`, `getgrnam`, `getgrgid`, `gethostbyname`, etc.). This proposal intends to replace ''nscd'' in Fedora with ''systemd-resolved'' for the `hosts` database and the ''sssd'' daemon for everything else. Accordingly, the `nscd` sub-package of glibc will be removed and obsoleted.

== Benefit to Fedora ==

While still maintained within the glibc source tree, ''nscd'' has received less than forty commits in the past three years and has gathered significant technical debt, and has bugs which are hard to fix. There are concurrency bugs in the shared mappings, cache unification (IPv4 vs. IPv6 vs. AF_UNSPEC) issues, and more which would require significant investment to fix in nscd. Such an investment seems like duplicate effort among our communities given the quality and state of ''sssd'', and ''systemd-resolved'' which is already proposed to be enabled by default from [[Changes/systemd-resolved | Fedora 33 onwards]].

At a high level, sssd and systemd-resolved together provide a caching solution that has feature parity with nscd, with systemd-resolved covering the hosts cache and sssd the rest. The removal of nscd from Fedora will: * move the user base over to a more modern solution for named services caching, and * reduce maintenance work on the Fedora glibc package and the duplication of effort on nscd upstream.

== Scope == * Proposal owners: The volume of work required is minimal, with the only change being the removal and obsolescence of the nscd sub-package offered by glibc which can be achieved by minor changes to the spec file. Since nscd is not installed by default, the affect on the distribution is minimal. Users who have installed nscd in an earlier release of Fedora will need to install and configure sssd instead.

* Other developers: `nss-pam-ldapd` has a weak dependency on nscd that will need to be removed. `libuser` has a build dependency on nscd that will also need to be removed.

* Release engineering: This change does not require coordination with or have impact on release engineering and does not require a mass rebuild.

* Policies and guidelines: N/A (not a System Wide Change) * Trademark approval: N/A (not needed for this Change) * Alignment with Objectives: Yes, this proposal aligns with the [https://docs.fedoraproject.org/en-US/project/objectives current objective] of "Fedora Minimization".

== Upgrade/compatibility impact == N/A (not a System Wide Change)

== User Experience == * Most users will be unaffected by this change because nscd is not installed by default. It is usually used on systems configured with LDAP, where nscd provides caching of remote queries. * On a system using nscd that is updated to Fedora 34 from a previous version, the system administrator will need to install and configure sssd to replace it after the update. Even when this is not done, the only visible affect will be slower resolution of named service queries due to a missing cache. * Users on a system running sssd and systemd-resolved instead of nscd shouldn't see any noticeable difference in system behaviour or latency in resolving named services.

== Dependencies == * `nss-pam-ldapd` has a weak dependency on nscd that will need to be removed. * `libuser` has a build dependency on nscd that will also need to be removed.

Both changes are minimal, requiring a removal of the dependency in the spec file, and a rebuild.

== Contingency Plan == * Contingency mechanism: Revert changes to glibc spec file and continue to ship nscd. Revert changes to libuser and nss-pam-ldapd packages; this will need to be done by the respective package maintainers. * Contingency deadline: Fedora 34 Beta Freeze * Blocks release? N/A (not a System Wide Change) * Blocks product? None

== Documentation == N/A (not a System Wide Change)