With "getent passwd | grep 1000" I get the same single entry as above.

This is a test system, not only there is no NIS and LDAP, but there is a single user right now.

/etc/passwd as follows

root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
syslog:x:101:102::/home/syslog:/bin/false
messagebus:x:103:104::/var/run/dbus:/bin/false
polkituser:x:104:105:PolicyKit,,,:/var/run/PolicyKit:/bin/false
hplip:x:106:7:HPLIP system user,,,:/var/run/hplip:/bin/false
avahi-autoipd:x:107:113:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false
avahi:x:108:114:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false
saned:x:109:117::/home/saned:/bin/false
callegar:x:1000:1000:Sergio Callegari:/home/callegar:/bin/bash
stunnel4:x:111:123::/var/run/stunnel4:/bin/false
sshd:x:110:65534::/var/run/sshd:/usr/sbin/nologin
pulse:x:112:119:PulseAudio daemon,,,:/var/run/pulse:/bin/false
clamav:x:113:125::/var/lib/clamav:/bin/false
postfix:x:102:103::/var/spool/postfix:/bin/false
usbmux:x:114:46:usbmux daemon,,,:/home/usbmux:/bin/false
rtkit:x:115:126:RealtimeKit,,,:/proc:/bin/false
oprofile:x:116:127:OProfile JIT user,,,:/var/lib/oprofile:/bin/bash
colord:x:105:106:colord colour management daemon,,,:/var/lib/colord:/bin/false
dhcpd:x:118:135::/var/run:/bin/false
timidity:x:119:136:TiMidity++ MIDI sequencer service:/etc/timidity:/bin/false
dnsmasq:x:121:65534:dnsmasq,,,:/var/lib/misc:/bin/false
whoopsie:x:122:128::/nonexistent:/bin/false
dcmtk:x:117:139::/var/lib/dcmtk/db:/bin/sh
uuidd:x:100:101::/run/uuidd:/bin/false
gpsd:x:123:20:GPSD system user,,,:/run/gpsd:/bin/false
systemd-timesync:x:124:142:systemd Time Synchronization,,,:/run/systemd:/bin/false
systemd-network:x:125:143:systemd Network Management,,,:/run/systemd/netif:/bin/false
systemd-resolve:x:126:144:systemd Resolver,,,:/run/systemd/resolve:/bin/false
systemd-bus-proxy:x:127:145:systemd Bus Proxy,,,:/run/systemd:/bin/false
kernoops:x:129:65534:Kernel Oops Tracking Daemon,,,:/:/bin/false
speech-dispatcher:x:130:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/false
sddm:x:120:137:Simple Desktop Display Manager:/var/lib/sddm:/bin/false

Here is /etc/group

root:x:0:
daemon:x:1:
bin:x:2:
sys:x:3:
adm:x:4:callegar,syslog
tty:x:5:
disk:x:6:
lp:x:7:callegar
mail:x:8:
news:x:9:
uucp:x:10:
man:x:12:
proxy:x:13:
kmem:x:15:
dialout:x:20:callegar
fax:x:21:callegar
voice:x:22:
cdrom:x:24:callegar
floppy:x:25:callegar
tape:x:26:
sudo:x:27:callegar
audio:x:29:pulse,timidity
dip:x:30:
www-data:x:33:
backup:x:34:
operator:x:37:
list:x:38:
irc:x:39:
src:x:40:
gnats:x:41:
shadow:x:42:
utmp:x:43:
video:x:44:
sasl:x:45:
plugdev:x:46:callegar
staff:x:50:callegar
games:x:60:
users:x:100:
nogroup:x:65534:
syslog:x:102:callegar
messagebus:x:104:
polkituser:x:105:
fuse:x:107:callegar
ssl-cert:x:108:
lpadmin:x:109:callegar
crontab:x:110:
mlocate:x:111:
ssh:x:112:
avahi-autoipd:x:113:
avahi:x:114:
netdev:x:115:
admin:x:116:callegar
saned:x:117:
callegar:x:1000:
sambashare:x:118:callegar
winbindd_priv:x:122:
stunnel4:x:123:
vboxusers:x:124:callegar
pulse:x:119:
pulse-access:x:120:
clamav:x:125:
postfix:x:103:
postdrop:x:121:
rtkit:x:126:
oprofile:x:127:
utempter:x:129:
bluetooth:x:131:
powerdev:x:132:
colord:x:106:
scanner:x:133:colord,callegar,saned
_cvsadmin:x:134:
pcscd:x:130:
dhcpd:x:135:
timidity:x:136:
nopasswdlogin:x:138:
whoopsie:x:128:
dcmtk:x:139:
uuidd:x:101:
systemd-journal:x:140:
systemd-journal-remote:x:141:
systemd-timesync:x:142:
systemd-network:x:143:
systemd-resolve:x:144:
systemd-bus-proxy:x:145:
input:x:146:
sddm:x:137: