Man pages › Compared with Linux and the BSDs

`idmapd(8)` on Solnix vs Linux and the BSDs

Solnix idmapd is the illumos Native Identity Mapping daemon at /usr/lib/idmapd. It maps Windows SIDs to UIDs/GIDs and back, and is managed by SMF as svc:/system/idmap. The Linux idmapd(8) in the bundle is a different program: rpc.idmapd, the NFSv4 ID <-> name mapper.

The manual pages

Solnix: idmapd(8) from pkgs.solnix.illumos-world-man · illumos.org
Linux: idmapd(8) nfs-utils-2.9.1

What Solnix runs

A default Solnix system runs the illumos idmapd, installed under /usr/lib (not in /usr/bin, /usr/sbin or /sbin). No other variants are shipped. The idmap(8) utility is its front end, and svcadm(8) and svcs(1) administer and query the service.

Differences

Compared with	Topic	What differs
Linux	what the daemon maps	Solnix idmapd maps Windows SIDs to POSIX UIDs/GIDs and conversely. Linux rpc.idmapd translates NFSv4 user and group IDs to names and back, for the NFSv4 kernel client and server. Source: Solnix idmapd(8) DESCRIPTION; Linux idmapd(8) NAME, DESCRIPTION
Linux	command line options	The Solnix SYNOPSIS is just `/usr/lib/idmapd` and documents no options. Linux rpc.idmapd takes `-h`, `-f`, `-v`, `-C`, `-S`, `-p` path and `-c` path. Flags such as `-f` for foreground do not exist on the Solnix page. Source: Solnix idmapd(8) SYNOPSIS; Linux idmapd(8) SYNOPSIS, options list
Linux	how the daemon is run	On Solnix, SMF manages idmapd as svc:/system/idmap. Use svcadm to enable, disable or restart it, and svcs to query it. The Linux page describes running rpc.idmapd directly (`-f` for foreground) and does not mention a service manager. Source: Solnix idmapd(8) NOTES; Linux idmapd(8) -f
Linux	authorization for administration	Administrative actions on the Solnix service require the solaris.smf.manage.idmap authorization. The Linux page mentions no such authorization. Source: Solnix idmapd(8) NOTES
Linux	configuration	Linux rpc.idmapd is configured through `/etc/idmapd.conf` (lookup mechanism, domain), and by the _nfsv4idmapdomain DNS text record when no domain is set. The Solnix page names no configuration file; it lists defaultdomain(5) under SEE ALSO and says nothing more. Source: Linux idmapd(8) DESCRIPTION; Solnix idmapd(8) SEE ALSO
Linux	database files	Solnix lists `/var/idmap/idmap.db` and `/var/run/idmap/idmap.db` as Project Private interfaces, so scripts should not depend on them. The Linux page names no such database; it mentions `/var/lib/nfs/rpc_pipefs` as the default RPC pipefs location (`-p`). Source: Solnix idmapd(8) ATTRIBUTES; Linux idmapd(8) -p
Linux	role in the NFSv4 client	On more recent Linux kernels only the NFSv4 server uses rpc.idmapd. The client uses nfsidmap(8) and falls back to rpc.idmapd only on a problem. The Solnix page does not mention NFS. Source: Linux idmapd(8) DESCRIPTION (note on recent kernels); Solnix idmapd(8) DESCRIPTION
FreeBSD, OpenBSD, NetBSD	no BSD counterpart in bundle	The bundle includes no idmapd page for FreeBSD, OpenBSD or NetBSD, so no comparison with them can be made from the manuals. Source: Bundle header: only a linux COUNTERPART is listed

Standards

POSIX: idmapd is not a POSIX.1-2024 utility.
Solnix: Interface Stability: svc:/system/idmap is Committed; /var/idmap/idmap.db and /var/run/idmap/idmap.db are Project Private.
Solnix: The page warns that the functionality of this daemon might change in a future release of the Solaris operating system.

Writing portable scripts

Do not assume idmapd means the same thing across systems: on Solnix it is SID/POSIX ID mapping, on Linux it is NFSv4 name mapping. Do not start it by hand in scripts; on Solnix use svcadm on svc:/system/idmap.

Every difference here is taken from the manual pages linked above: Solnix's published page, Linux (man-pages and the GNU and util-linux manuals), FreeBSD, OpenBSD and NetBSD. Each row names its source. Where a manual is silent, this page is too. Compiled 2026-10-26. Found a mistake? Mail hackers@lists.solnix.io.