Ora-01034:oracle not available ora-27101:shared memory realm does not exit

Oracle is installed on virtual machine Linux, and there are a series of errors in the configuration of Oracle that keeps the host connected to the virtual machine, sharing the entire process

Turn on Linux on the Oracle Monitor, open the database, there are the following errors

Tns-12545:connect failed because target host or object does not exist  
Tns-12560:tns:protocol Error   &NBSP
Tns-00515:connect failed because target host or object does not exist    
Linux Erro R:99:cannot assign requested address


Connect the host client to the virtual machine Linux system ORACLE error follows:
Ora-01034:oracle not available
Ora-27101:shared Memory Realm does not e
Linux error:2: No such file or directory


First look at connect faile D because target host or object does not exist is because I changed the IP on Linux
, and I looked at my host name as localhost not my redhat before, I forgot to change my/etc/ Hosts file,
Keep the current system IP and/etc/hosts files consistent.
then tnping the Local service name and error: tns-03505:failed to resolve name
I looked at Listener.ora and Sqlnet.ora and Tnsname.ora, the original Sqlnet.ora connection is Ezconnect
to ensure that remote also can connect to your Linux server will be changed:
NAMES . Directory_path= (tnsnames,ezconnect)
then executes tnping ORCL and succeeds. The
then tnsping the local service name on my host is successful and the connection is fine.