오라클 19c /etc/hosts 권한 부족시 발생하는 문제

OS환경 : Oracle Linux 7.5 (64bit)

DB 환경 : Oracle Database 19.3.0.0

방법 : 오라클 19c /etc/hosts 권한 부족시 발생하는 문제

보안 조치로 인해 /etc/hosts 파일의 권한이 부족한 경우 오라클DB에 미치는 영향에 대해 알아봄

3가지 테스트를 진행함

테스트1. 리스너 포트 1521 인 경우(동적 리스너)

테스트2. 리스너 포트 1522 에 local_listener 등록한 경우(동적 리스너)

테스트3. 리스너 포트 1523 에 local_listener 등록하지 않은 경우(정적리스너)

테스트1. 리스너 포트 1521 인 경우(동적 리스너)

기존 /etc/hosts 파일 권한 확인

1 2	$ ls -al /etc/hosts -rw-r--r--. 1 root root 182 Aug 12 19:27 /etc/hosts

644 권한이 부여되어있음(소유자는 읽기쓰기 가능, 그룹원과 일반사용자는 읽기만 가능)

현재 권한이 정상적으로 부여되어있음

기존 db, 리스너 상태 확인(리스너 기본 1521포트, local_listener 파라미터 미사용)

리스너 상태 확인
$ lsnrctl status
 
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 10:27:45
 
Copyright (c) 1991, 2019, Oracle.  All rights reserved.
 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle19)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date                18-SEP-2020 10:23:35
Uptime                    0 days 0 hr. 4 min. 9 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /app/oracle/product/19c/network/admin/listener.ora
Listener Log File         /app/oracle/diag/tnslsnr/oracle19/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
Services Summary...
Service "orcl19" has 1 instance(s).
  Instance "orcl19", status READY, has 1 handler(s) for this service...
Service "orcl19XDB" has 1 instance(s).
  Instance "orcl19", status READY, has 1 handler(s) for this service...
The command completed successfully
 
db 상태 확인
$ sqlplus / as sysdba
 
SQL*Plus: Release 19.0.0.0.0 - Production on Fri Sep 18 10:27:51 2020
Version 19.3.0.0.0
 
Copyright (c) 1982, 2019, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
 
SQL> select instance_name, status, version from v$instance;
 
INSTANCE_NAME     STATUS       VERSION
---------------- ------------ -----------------
orcl19         OPEN          19.0.0.0.0
 
local_listener 파라미터 확인
SQL> show parameter local_listener
 
NAME                     TYPE     VALUE
------------------------------------ ----------- ------------------------------
local_listener                 string

기존 db, 리스너 재기동 확인

db 종료
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
 
db 기동
SQL> startup
ORACLE instance started.
 
Total System Global Area 2516581464 bytes
Fixed Size            8899672 bytes
Variable Size          553648128 bytes
Database Buffers     1946157056 bytes
Redo Buffers            7876608 bytes
Database mounted.
Database opened.
 
리스너 종료
$ lsnrctl stop
 
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 10:31:25
 
Copyright (c) 1991, 2019, Oracle.  All rights reserved.
 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle19)(PORT=1521)))
The command completed successfully
 
리스너 기동
$ lsnrctl start
 
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 10:31:28
 
Copyright (c) 1991, 2019, Oracle.  All rights reserved.
 
Starting /app/oracle/product/19c/bin/tnslsnr: please wait...
 
TNSLSNR for Linux: Version 19.0.0.0.0 - Production
System parameter file is /app/oracle/product/19c/network/admin/listener.ora
Log messages written to /app/oracle/diag/tnslsnr/oracle19/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1521)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle19)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date                18-SEP-2020 10:31:28
Uptime                    0 days 0 hr. 0 min. 0 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /app/oracle/product/19c/network/admin/listener.ora
Listener Log File         /app/oracle/diag/tnslsnr/oracle19/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
The listener supports no services
The command completed successfully

db 및 리스너 재기동시에도 문제 없이 잘 기동됨

/etc/hosts 파일 권한 변경

# chmod 600 /etc/hosts
# ls -al /etc/hosts
-rw-------. 1 root root 182 Aug 12 19:27 /etc/hosts

600 권한으로 변경함(소유자는 읽기쓰기 가능, 그룹원과 일반사용자는 읽기도 불가능)

파일 권한 변경 직후

alert log, listener.log 는 특이사항 없음

$ tail -f /app/oracle/diag/rdbms/orcl19/orcl19/trace/alert_orcl19.log 
이상없음
 
$ tail -f /app/oracle/diag/tnslsnr/oracle19/listener/trace/listener.log 
이상없음

db, 리스너 종료

리스너 종료
$ lsnrctl stop
 
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 11:58:04
 
Copyright (c) 1991, 2019, Oracle.  All rights reserved.
 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle19)(PORT=1521)))
The command completed successfully
 
db 종료
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.

정상적으로 종료됨

리스너, db 기동

리스너 기동
$ lsnrctl start
 
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 12:00:02
 
Copyright (c) 1991, 2019, Oracle.  All rights reserved.
 
Starting /app/oracle/product/19c/bin/tnslsnr: please wait...
 
TNSLSNR for Linux: Version 19.0.0.0.0 - Production
System parameter file is /app/oracle/product/19c/network/admin/listener.ora
Log messages written to /app/oracle/diag/tnslsnr/oracle19/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1521)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle19)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date                18-SEP-2020 12:00:02
Uptime                    0 days 0 hr. 0 min. 0 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /app/oracle/product/19c/network/admin/listener.ora
Listener Log File         /app/oracle/diag/tnslsnr/oracle19/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
The listener supports no services
The command completed successfully
 
db 기동
SQL> startup
ORACLE instance started.
 
Total System Global Area 2516581464 bytes
Fixed Size            8899672 bytes
Variable Size          553648128 bytes
Database Buffers     1946157056 bytes
Redo Buffers            7876608 bytes
Database mounted.
Database opened.

기동시 alert log, listener.log 도 특이사항 없음

다른 서버에서 접속 테스트

다른 서버 tnsnames.ora
$ cat tnsnames.ora 
# tnsnames.ora Network Configuration File: /app/oracle/product/19c/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.
 
ORCL19 =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.10.240)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl19)
    )
  )
 
다른 서버에서 기존 서버로 tnsping
$ tnsping orcl19
 
TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 12:08:45
 
Copyright (c) 1997, 2020, Oracle.  All rights reserved.
 
Used parameter files:
 
 
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.10.240)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orcl19)))
OK (0 msec)
 
다른 서버에서 기존 서버로 sqlplus 접속테스트
$ sqlplus system/oracle@orcl19
 
SQL*Plus: Release 19.0.0.0.0 - Production on Fri Sep 18 12:10:28 2020
Version 19.8.0.0.0
 
Copyright (c) 1982, 2020, Oracle.  All rights reserved.
 
Last Successful login time: Fri Sep 18 2020 12:08:52 +09:00
 
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
 
SQL> select host_name from v$instance;
 
HOST_NAME
----------------------------------------------------------------
oracle19

접속이 정상적으로 가능함

테스트2. 리스너 포트 1522 에 local_listener 등록한 경우(동적 리스너)

테스트를 위해 기존 포트 리스너 및 db 모두 종료

$ lsnrctl stop
로그 생략
 
SQL> shutdown immediate
로그 생략

1522 포트 동적 리스너 및 db 기동 후 local_listener 파라미터 적용

listener.ora 파일 확인
$ cat /app/oracle/product/19c/network/admin/listener.ora
LISTENER2 =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = oracle19)(PORT = 1522))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1522))
    )
  )
 
tnsnames.ora 파일 확인
$ cat /app/oracle/product/19c/network/admin/tnsnames.ora 
ORCL19_L2 =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = oracle19)(PORT = 1522))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl19)
    )
  )
 
1522 리스너 기동
$ lsnrctl start listener2
 
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 12:19:37
 
Copyright (c) 1991, 2019, Oracle.  All rights reserved.
 
Starting /app/oracle/product/19c/bin/tnslsnr: please wait...
 
TNSLSNR for Linux: Version 19.0.0.0.0 - Production
System parameter file is /app/oracle/product/19c/network/admin/listener.ora
Log messages written to /app/oracle/diag/tnslsnr/oracle19/listener2/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1522)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1522)))
 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle19)(PORT=1522)))
STATUS of the LISTENER
------------------------
Alias                     listener2
Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date                18-SEP-2020 12:19:37
Uptime                    0 days 0 hr. 0 min. 0 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /app/oracle/product/19c/network/admin/listener.ora
Listener Log File         /app/oracle/diag/tnslsnr/oracle19/listener2/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1522)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1522)))
The listener supports no services
The command completed successfully
 
db 기동
SQL> startup
ORACLE instance started.
 
Total System Global Area 2516581464 bytes
Fixed Size            8899672 bytes
Variable Size          553648128 bytes
Database Buffers     1946157056 bytes
Redo Buffers            7876608 bytes
Database mounted.
Database opened.
 
local_listener 파라미터 설정
SQL> alter system set local_listener='ORCL19_L2'; 
 
System altered.
 
local_listener 파라미터 확인
SQL> show parameter local_listener
 
NAME                     TYPE     VALUE
------------------------------------ ----------- ------------------------------
local_listener                 string     ORCL19_L2

기동시 alert log, listener.log 도 특이사항 없음

리스너 상태 확인

$ lsnrctl status listener2
 
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 12:23:39
 
Copyright (c) 1991, 2019, Oracle.  All rights reserved.
 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle19)(PORT=1522)))
STATUS of the LISTENER
------------------------
Alias                     listener2
Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date                18-SEP-2020 12:19:37
Uptime                    0 days 0 hr. 4 min. 1 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /app/oracle/product/19c/network/admin/listener.ora
Listener Log File         /app/oracle/diag/tnslsnr/oracle19/listener2/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1522)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1522)))
Services Summary...
Service "orcl19" has 1 instance(s).
  Instance "orcl19", status READY, has 1 handler(s) for this service...
Service "orcl19XDB" has 1 instance(s).
  Instance "orcl19", status READY, has 1 handler(s) for this service...
The command completed successfully

다른 서버에서 접속 테스트

다른 서버 tnsnames.ora
$ cat tnsnames.ora 
# tnsnames.ora Network Configuration File: /app/oracle/product/19c/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.
 
ORCL19_L2 =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.10.240)(PORT = 1522))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl19)
    )
  )
 
다른 서버에서 기존 서버로 tnsping
$ tnsping orcl19_l2
 
TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 12:25:01
 
Copyright (c) 1997, 2020, Oracle.  All rights reserved.
 
Used parameter files:
 
 
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.10.240)(PORT = 1522)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orcl19)))
OK (10 msec)
 
다른 서버에서 기존 서버로 sqlplus 접속테스트
$ sqlplus system/oracle@orcl19_l2
 
SQL*Plus: Release 19.0.0.0.0 - Production on Fri Sep 18 12:25:17 2020
Version 19.8.0.0.0
 
Copyright (c) 1982, 2020, Oracle.  All rights reserved.
 
Last Successful login time: Fri Sep 18 2020 12:10:29 +09:00
 
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
 
SQL> select host_name from v$instance;
 
HOST_NAME
----------------------------------------------------------------
oracle19

접속이 정상적으로 가능함

테스트3. 리스너 포트 1523 에 local_listener 등록하지 않은 경우(정적리스너)

테스트를 위해 1522 포트 리스너 종료 및 local_listener 파라미터 값 삭제 후 db 종료

$ lsnrctl stop listener2
로그 생략
 
SQL> alter system set local_listener='';
 
System altered.
 
SQL> shutdown immediate
로그 생략

1523 포트 정적 리스너 및 db 기동

listener.ora 파일 확인
$ cat /app/oracle/product/19c/network/admin/listener.ora
LISTENER3 =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = oracle19)(PORT = 1523))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1523))
    )
  )
 
SID_LIST_LISTENER3 =
 (SID_LIST =
  (SID_DESC =
   (ORACLE_HOME = /app/oracle/product/19c)
   (SID_NAME = orcl19)
  )
 )
 
tnsnames.ora 파일 확인
$ cat /app/oracle/product/19c/network/admin/tnsnames.ora 
ORCL19_L3 =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = oracle19)(PORT = 1523))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl19)
    )
  )
 
1523 리스너 기동
$ lsnrctl start listener3
 
LSNRCTL for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 12:33:58
 
Copyright (c) 1991, 2019, Oracle.  All rights reserved.
 
Starting /app/oracle/product/19c/bin/tnslsnr: please wait...
 
TNSLSNR for Linux: Version 19.0.0.0.0 - Production
System parameter file is /app/oracle/product/19c/network/admin/listener.ora
Log messages written to /app/oracle/diag/tnslsnr/oracle19/listener3/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1523)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1523)))
 
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle19)(PORT=1523)))
STATUS of the LISTENER
------------------------
Alias                     listener3
Version                   TNSLSNR for Linux: Version 19.0.0.0.0 - Production
Start Date                18-SEP-2020 12:33:58
Uptime                    0 days 0 hr. 0 min. 0 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /app/oracle/product/19c/network/admin/listener.ora
Listener Log File         /app/oracle/diag/tnslsnr/oracle19/listener3/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=oracle19)(PORT=1523)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1523)))
Services Summary...
Service "orcl19" has 1 instance(s).
  Instance "orcl19", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
 
db 기동
SQL> startup
ORACLE instance started.
 
Total System Global Area 2516581464 bytes
Fixed Size            8899672 bytes
Variable Size          553648128 bytes
Database Buffers     1946157056 bytes
Redo Buffers            7876608 bytes
Database mounted.
Database opened.

기동시 alert log, listener.log 도 특이사항 없음

다른 서버에서 접속 테스트

다른 서버 tnsnames.ora
$ cat /app/oracle/product/19c/network/admin/tnsnames.ora
# tnsnames.ora Network Configuration File: /app/oracle/product/19c/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.
 
ORCL19_L3 =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.10.240)(PORT = 1523))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl19)
    )
  )
 
다른 서버에서 기존 서버로 tnsping
$ tnsping orcl19_l3
 
TNS Ping Utility for Linux: Version 19.0.0.0.0 - Production on 18-SEP-2020 12:40:59
 
Copyright (c) 1997, 2020, Oracle.  All rights reserved.
 
Used parameter files:
 
 
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.10.240)(PORT = 1523)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orcl19)))
OK (0 msec)
 
다른 서버에서 기존 서버로 sqlplus 접속테스트
$ sqlplus system/oracle@orcl19_l3
 
SQL*Plus: Release 19.0.0.0.0 - Production on Fri Sep 18 12:41:09 2020
Version 19.8.0.0.0
 
Copyright (c) 1982, 2020, Oracle.  All rights reserved.
 
Last Successful login time: Fri Sep 18 2020 12:25:18 +09:00
 
Connected to:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.3.0.0.0
 
SQL> select host_name from v$instance;
 
HOST_NAME
----------------------------------------------------------------
oracle19

접속이 정상적으로 가능함

결론

/etc/hosts 권한 부족시에도 oracle db 접속이 정상적으로 가능함

접속이 정상적으로 되더라도 /etc/hosts 권한을 600으로 하는건 추후 오라클 DB운영에 문제가 발생할 수 있으니

644로 유지해줘야함

접속이 가능한 이유?

linux 6 버전까지는 로컬(본인서버)에 ping을 날릴때 /etc/hosts에 있는 hostname을 참조해서 ping을 날림

그래서 /etc/hosts 권한이 없는 사용자의 경우 ping 시도시 [ ping: unknown host ] 메세지가 발생함

하지만 linux 7 버전부터는 ping을 날릴때 /etc/hosts 에 권한이 없는 사용자여도 ping 시도시 정상적으로 ping이 성공함

oracle listener의 경우 listener.ora파일에 HOST = 부분에 ip가 아닌 hostname 으로 작성한 경우

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = oracle19)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

/etc/hosts 파일의 hostname을 보고 리스너를 기동한다고 알고있음

하지만 linux7의 경우 /etc/hosts 파일을 읽을 수 없는 경우 또 다른 어떤 파일을 참조하여 hostname을 찾는듯함

linux 6 버전에서는 /etc/hosts 파일을 읽을 수 없는 경우 리스너 기동도 실패함

참조 : 오라클 11g R2 /etc/hosts 권한 부족시 발생하는 문제 https://positivemh.tistory.com/663

linux 6 버전에서 /etc/hosts 권한 600 부여 후 로컬 호스트네임으로 ping 테스트

/etc/hosts 내용확인
# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.0.30    ORACLE11
 
/etc/hosts 권한 확인
# ls -al /etc/hosts
-rw-------. 1 root root 181 Oct 15  2019 /etc/hosts
 
권한 있는 유저로 ping
# ping oracle11
PING ORACLE11 (192.168.0.30) 56(84) bytes of data.
64 bytes from ORACLE11 (192.168.0.30): icmp_seq=1 ttl=64 time=0.274 ms
64 bytes from ORACLE11 (192.168.0.30): icmp_seq=2 ttl=64 time=0.035 ms
64 bytes from ORACLE11 (192.168.0.30): icmp_seq=3 ttl=64 time=0.041 ms
64 bytes from ORACLE11 (192.168.0.30): icmp_seq=4 ttl=64 time=0.034 ms
 
권한 없는 유저로 ping
$ ping oracle11
ping: unknown host oracle11

권한 없는 유저는 ping이 실패함

linux 7 버전에서 /etc/hosts 권한 600 부여 후 로컬 호스트네임으로 ping 테스트

/etc/hosts 내용확인
# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.10.240 oracle19
 
/etc/hosts 권한 확인
# ls -al /etc/hosts
-rw-------. 1 root root 182 Aug 12 19:27 /etc/hosts
 
권한 있는 유저로 ping
# ping oracle19
PING oracle19 (192.168.10.240) 56(84) bytes of data.
64 bytes from oracle19 (192.168.10.240): icmp_seq=1 ttl=64 time=0.045 ms
64 bytes from oracle19 (192.168.10.240): icmp_seq=2 ttl=64 time=0.044 ms
64 bytes from oracle19 (192.168.10.240): icmp_seq=3 ttl=64 time=0.044 ms
64 bytes from oracle19 (192.168.10.240): icmp_seq=4 ttl=64 time=0.044 ms
 
권한 없는 유저로 ping
$ ping oracle19
PING oracle19 (192.168.10.240) 56(84) bytes of data.
64 bytes from oracle19 (192.168.10.240): icmp_seq=1 ttl=64 time=0.037 ms
64 bytes from oracle19 (192.168.10.240): icmp_seq=2 ttl=64 time=0.065 ms
64 bytes from oracle19 (192.168.10.240): icmp_seq=3 ttl=64 time=0.056 ms
64 bytes from oracle19 (192.168.10.240): icmp_seq=4 ttl=64 time=0.056 ms

/etc/hosts 권한이 없는 유저도 ping 이 성공함

/etc/hostname 파일을 보고 읽는것으로 예상하고 

해당파일도 600으로 권한 변경 후 테스트하였지만 결과는 동일했음

$ ls -al /etc/hostname 
-rw-------. 1 root root 9 Aug 12 19:27 /etc/hostname

참조 : 

오라클 11gR2 /etc/hosts 권한 부족시 발생하는 문제(Oracle Linux 6) https://positivemh.tistory.com/663

https://docs.oracle.com/en/database/oracle/oracle-database/19/netag/configuring-and-administering-oracle-net-listener.html#GUID-C3C40DBA-4282-41E1-9562-4B8B10947C4E

https://m.blog.naver.com/renucs/221038877657