DH_INSTALLNSS(1)

💅 DH_INSTALLNSS 💅

okay so bestie, this is dh_installnss(1) from the User Contributed Perl Documentation section of the manual. it's a whole manual page, she's got lore, she's got range, and she's about to make your /etc/nsswitch.conf look right. 🎀

---

✨ NAME ✨

dh_installnss — enable NSS services 🦋

---

🌸 SYNOPSIS 🌸

dh_installnss [debhelper options]

---

💖 DESCRIPTION 💖

so dh_installnss is a debhelper program and her whole job, her entire purpose, her main character moment, is injecting NSS (that's Name Service Switch, iykyk) services into /etc/nsswitch.conf. that's it. that's the gig. 💅

---

🎀 FILES 🎀

• debian/package.nss — this file lists the services to inject into /etc/nsswitch.conf when a package is configured, and the ones to remove when a package is removed or purged. bestie behaviour fr fr.

every line in that file (we call each one a directive) should look like this:

db position service action condition

and here's what each field is actually saying:

• db — the NSS database where the service is gonna get added. usually it's "hosts". classic.
• position — where to add the NSS service.

the possible values are "first", "last", "before=service", "after=service", plus these three pseudo-positions: "remove-only", "database-add" and "database-require".

the pseudo-position "remove-only" is for marking services that are NOT gonna be added when the package installs, but WILL be removed when it deinstalls (think legacy services, the exes that never leave 🫠).

the pseudo-position "database-add" is used to request adding a non-standard NSS database to /etc/nsswitch.conf during the package's installation, and removing it during deinstallation. ⚠️ when you use "database-add", every other field in the directive should be left empty. no extras, she's minimalist.

the pseudo-position "database-require" is announcing that one or more services in the nss file are gonna be installed under a non-standard NSS database that some other package added. ⚠️ when you use "database-require", again, all the other fields in the directive should be left empty.

• service — the name of the NSS service to add. iconic, no notes.
• action — optional action specification, and it looks like "[STATE=ACTION]".
• condition — optional set of conditions that better define when a service should (or should not) get installed.

only one kind of condition is defined right now: "skip-if-present=service,service,...".

also, literally anything between a # character and the end of the line gets ignored. comments, we love her. 💜

---

🌈 EXAMPLES 🌈

an example debian/nss file could look like this:

hosts before=dns mdns4
hosts before=mdns4 mdns4_minimal [NOTFOUND=return]
hosts remove-only mdns    # In case the user manually added it

so after this package installs, the original configuration of the hosts database in /etc/nsswitch.conf changes from:

hosts:    files dns

to:

hosts:    files mdns4_minimal [NOTFOUND=return] mdns4 dns

the glow up is REAL. ✨

---

⚠️ CAVEATS ⚠️

💀 Non-standard NSS databases 💀

okay this is the serious part, listen up bestie, no cap:

directives in a package.nss file can reference a non-standard NSS database only if that database has first been declared with a "database-add" or "database-require" directive in the same file. same file. don't try it anywhere else.

and what counts as a non-standard NSS database? it's all databases that are not defined in /etc/nsswitch.conf as shipped by the package base-files. that's the line.

if a directive references an undeclared non-standard NSS database (like "somedb"), dh_installnss will exit with the error message "Unknown NSS database 'somedb'". 💀

a non-standard NSS database can be declared by at most one installed package. in other words: if the directives in the nss files of two packages, A and B, reference the same non-standard NSS database "somedb", and both packages can be installed at the same time, you gotta implement one of these two solutions:

1. Package A supplies the "somedb database-add" directive, package B Pre-Depends on A and uses a "somedb database-require" directive.
2. The shared package C supplies the "somedb database-add" directive, both package A and B Pre-Depend on C and use a "somedb database-require" directive.

pick one, don't freestyle it. 🙈

---

👀 SEE ALSO 👀

• debhelper(7)
• this program is a debhelper addon. periodt.

---

👑 AUTHOR 👑

Gioele Barabucci <gioele@svario.it> — the icon who wrote this, we stan 🫶

---

and that's a wrap, my love 💖 this page is from perl v5.40.1, dated 2025-12-08, and you're officially NSS-pilled now. go forth and slay your nsswitch.conf. 🦋✨🎀