# https://docs.oracle.com/en/database/oracle/oracle-database/19/cwlin/identifying-an-oracle-software-owner-user-account.html#GUID-0A95F4B1-1045-455D-9897-A23012E4E27F

$ grep "oinstall" /etc/group
oinstall:x:54321:grid,oracle

$ id oracle
uid=54321(oracle) gid=54321(oinstall) groups=54321(oinstall),54322(dba), 
54323(oper),54324(backupdba),54325(dgdba),54326(kmdba),54327(asmdba),54330(racdba)


$ id grid
uid=54331(grid) gid=54321(oinstall) groups=54321(oinstall),54322(dba),
54327(asmdba),54328(asmoper),54329(asmadmin),54330(racdba)

# extract from /etc/group

oinstall:x:54321:
dba:x:54322:oracle,grid
oper:x:54323:oracle
backupdba:x:54324:oracle
dgdba:x:54325:oracle
kmdba:x:54326:oracle
racdba:x:54330:oracle,grid
asmoper:x:54327:grid
asmdba:x:54328:grid,oracle
asmadmin:x:54329:grid