/usr/share/postgresql/9.5/pg_ident.conf.sample is in postgresql-9.5 9.5.14-0ubuntu0.16.04.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | # PostgreSQL User Name Maps
# =========================
#
# Refer to the PostgreSQL documentation, chapter "Client
# Authentication" for a complete description. A short synopsis
# follows.
#
# This file controls PostgreSQL user name mapping. It maps external
# user names to their corresponding PostgreSQL user names. Records
# are of the form:
#
# MAPNAME SYSTEM-USERNAME PG-USERNAME
#
# (The uppercase quantities must be replaced by actual values.)
#
# MAPNAME is the (otherwise freely chosen) map name that was used in
# pg_hba.conf. SYSTEM-USERNAME is the detected user name of the
# client. PG-USERNAME is the requested PostgreSQL user name. The
# existence of a record specifies that SYSTEM-USERNAME may connect as
# PG-USERNAME.
#
# If SYSTEM-USERNAME starts with a slash (/), it will be treated as a
# regular expression. Optionally this can contain a capture (a
# parenthesized subexpression). The substring matching the capture
# will be substituted for \1 (backslash-one) if present in
# PG-USERNAME.
#
# Multiple maps may be specified in this file and used by pg_hba.conf.
#
# No map names are defined in the default configuration. If all
# system user names and PostgreSQL user names are the same, you don't
# need anything in this file.
#
# This file is read on server startup and when the postmaster receives
# a SIGHUP signal. If you edit the file on a running system, you have
# to SIGHUP the postmaster for the changes to take effect. You can
# use "pg_ctl reload" to do that.
# Put your actual configuration here
# ----------------------------------
# MAPNAME SYSTEM-USERNAME PG-USERNAME
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