/usr/share/bash-completion/completions/systemctl is in systemd 215-17+deb8u7.
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 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226  | # systemctl(1) completion                                 -*- shell-script -*-
#
# This file is part of systemd.
#
# Copyright 2010 Ran Benita
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
#
# systemd is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with systemd; If not, see <http://www.gnu.org/licenses/>.
__systemctl() {
        local mode=$1; shift 1
        systemctl $mode --full --no-legend "$@"
}
__systemd_properties() {
        local mode=$1
        { __systemctl $mode show --all;
         /lib/systemd/systemd --dump-configuration-items; } |
        while IFS='=' read -r key value; do
            [[ $value ]] && echo "$key"
        done
}
__contains_word () {
        local w word=$1; shift
        for w in "$@"; do
                [[ $w = "$word" ]] && return
        done
}
__filter_units_by_property () {
        local mode=$1 property=$2 value=$3 ; shift 3
        local units=("$@")
        local props
        IFS=$'\n' read -rd '' -a props < \
            <(__systemctl $mode show --property "$property" -- "${units[@]}")
        for ((i=0; $i < ${#units[*]}; i++)); do
                if [[ "${props[i]}" = "$property=$value" ]]; then
                        echo " ${units[i]}"
                fi
        done
}
__get_all_units      () { __systemctl $1 list-units --all \
        | { while read -r a b; do echo " $a"; done; }; }
__get_active_units   () { __systemctl $1 list-units       \
        | { while read -r a b; do echo " $a"; done; }; }
__get_startable_units () { __systemctl $1 list-units --all -t service,timer,socket,mount,automount,path,snapshot,swap \
        | { while read -r a b c d; do [[ $c == "inactive" || $c == "failed" ]] && echo " $a"; done; }; }
__get_failed_units   () { __systemctl $1 list-units       \
        | { while read -r a b c d; do [[ $c == "failed"   ]] && echo " $a"; done; }; }
__get_enabled_units  () { __systemctl $1 list-unit-files  \
        | { while read -r a b c  ; do [[ $b == "enabled"  ]] && echo " $a"; done; }; }
__get_disabled_units () { __systemctl $1 list-unit-files  \
        | { while read -r a b c  ; do [[ $b == "disabled" ]] && echo " $a"; done; }; }
__get_masked_units   () { __systemctl $1 list-unit-files  \
        | { while read -r a b c  ; do [[ $b == "masked"   ]] && echo " $a"; done; }; }
_systemctl () {
        local cur=${COMP_WORDS[COMP_CWORD]} prev=${COMP_WORDS[COMP_CWORD-1]}
        local i verb comps mode
        local -A OPTS=(
               [STANDALONE]='--all -a --reverse --after --before --defaults --fail --ignore-dependencies --failed --force -f --full -l --global
                             --help -h --no-ask-password --no-block --no-legend --no-pager --no-reload --no-wall
                             --quiet -q --privileged -P --system --user --version --runtime --recursive -r'
                      [ARG]='--host -H --kill-who --property -p --signal -s --type -t --state --root'
        )
        if __contains_word "--user" ${COMP_WORDS[*]}; then
            mode=--user
        else
            mode=--system
        fi
        if __contains_word "$prev" ${OPTS[ARG]}; then
                case $prev in
                        --signal|-s)
                                comps=$(compgen -A signal)
                        ;;
                        --type|-t)
                                comps='automount device mount path service snapshot socket swap target timer'
                        ;;
                        --state)
                                comps='loaded not-found stub
                                       active inactive
                                       dead elapsed exited listening mounted plugged running waiting'
                        ;;
                        --kill-who)
                                comps='all control main'
                        ;;
                        --root)
                                comps=$(compgen -A directory -- "$cur" )
                                compopt -o filenames
                        ;;
                        --host|-H)
                                comps=$(compgen -A hostname)
                        ;;
                        --property|-p)
                                comps=$(__systemd_properties $mode)
                        ;;
                esac
                COMPREPLY=( $(compgen -W '$comps' -- "$cur") )
                return 0
        fi
        if [[ "$cur" = -* ]]; then
                COMPREPLY=( $(compgen -W '${OPTS[*]}' -- "$cur") )
                return 0
        fi
        local -A VERBS=(
                [ALL_UNITS]='is-active is-failed is-enabled status show cat mask preset help list-dependencies'
            [ENABLED_UNITS]='disable'
           [DISABLED_UNITS]='enable'
        [REENABLABLE_UNITS]='reenable'
             [FAILED_UNITS]='reset-failed'
          [STARTABLE_UNITS]='start'
          [STOPPABLE_UNITS]='stop condstop kill try-restart condrestart'
         [ISOLATABLE_UNITS]='isolate'
         [RELOADABLE_UNITS]='reload condreload reload-or-try-restart force-reload'
        [RESTARTABLE_UNITS]='restart reload-or-restart'
             [MASKED_UNITS]='unmask'
                     [JOBS]='cancel'
                [SNAPSHOTS]='delete'
                     [ENVS]='set-environment unset-environment'
               [STANDALONE]='daemon-reexec daemon-reload default
                             emergency exit halt hibernate hybrid-sleep kexec list-jobs
                             list-sockets list-timers list-units list-unit-files poweroff
                             reboot rescue show-environment suspend get-default'
                     [NAME]='snapshot'
                     [FILE]='link'
                  [TARGETS]='set-default'
        )
        for ((i=0; i < COMP_CWORD; i++)); do
                if __contains_word "${COMP_WORDS[i]}" ${VERBS[*]} &&
                 ! __contains_word "${COMP_WORDS[i-1]}" ${OPTS[ARG]}; then
                        verb=${COMP_WORDS[i]}
                        break
                fi
        done
        if [[ -z $verb ]]; then
                comps="${VERBS[*]}"
        elif __contains_word "$verb" ${VERBS[ALL_UNITS]}; then
                comps=$( __get_all_units $mode )
        elif __contains_word "$verb" ${VERBS[ENABLED_UNITS]}; then
                comps=$( __get_enabled_units $mode )
        elif __contains_word "$verb" ${VERBS[DISABLED_UNITS]}; then
                comps=$( __get_disabled_units $mode )
        elif __contains_word "$verb" ${VERBS[REENABLABLE_UNITS]}; then
                comps=$( __get_disabled_units $mode;
                         __get_enabled_units $mode )
        elif __contains_word "$verb" ${VERBS[STARTABLE_UNITS]}; then
                comps=$( __filter_units_by_property $mode CanStart yes \
                      $( __get_startable_units $mode))
        elif __contains_word "$verb" ${VERBS[RESTARTABLE_UNITS]}; then
                comps=$( __filter_units_by_property $mode CanStart yes \
                      $( __get_all_units $mode \
                        | while read -r line; do \
                                [[ "$line" =~ \.(device|snapshot|socket|timer)$ ]] || echo " $line"; \
                        done ))
        elif __contains_word "$verb" ${VERBS[STOPPABLE_UNITS]}; then
                comps=$( __filter_units_by_property $mode CanStop yes \
                      $( __get_active_units $mode ) )
        elif __contains_word "$verb" ${VERBS[RELOADABLE_UNITS]}; then
                comps=$( __filter_units_by_property $mode CanReload yes \
                      $( __get_active_units $mode ) )
        elif __contains_word "$verb" ${VERBS[ISOLATABLE_UNITS]}; then
                comps=$( __filter_units_by_property $mode AllowIsolate yes \
                      $( __get_all_units $mode ) )
        elif __contains_word "$verb" ${VERBS[FAILED_UNITS]}; then
                comps=$( __get_failed_units $mode )
        elif __contains_word "$verb" ${VERBS[MASKED_UNITS]}; then
                comps=$( __get_masked_units $mode )
        elif __contains_word "$verb" ${VERBS[STANDALONE]} ${VERBS[NAME]}; then
                comps=''
        elif __contains_word "$verb" ${VERBS[JOBS]}; then
                comps=$( __systemctl $mode list-jobs | { while read -r a b; do echo " $a"; done; } )
        elif __contains_word "$verb" ${VERBS[SNAPSHOTS]}; then
                comps=$( __systemctl $mode list-units --type snapshot --full --all \
                        | { while read -r a b; do echo " $a"; done; } )
        elif __contains_word "$verb" ${VERBS[ENVS]}; then
                comps=$( __systemctl $mode show-environment \
                    | while read -r line; do echo " ${line%%=*}=";done )
                compopt -o nospace
        elif __contains_word "$verb" ${VERBS[FILE]}; then
                comps=$( compgen -A file -- "$cur" )
                compopt -o filenames
        elif __contains_word "$verb" ${VERBS[TARGETS]}; then
                comps=$( __systemctl $mode list-unit-files --type target --full --all \
                        | { while read -r a b; do echo " $a"; done; } )
        fi
        COMPREPLY=( $(compgen -W '$comps' -- "$cur") )
        return 0
}
complete -F _systemctl systemctl
 |