Install Postgresql from source on CentOS 7

In this article, let us review how to install postgreSQL 9.2.24 database on Centos 7 from source code.


Step 1: Download postgreSQL source code

Download From the postgreSQL download site.

# wget https://ftp.postgresql.org/pub/source/v9.2.24/postgresql-9.2.24.tar.gz

Step 2: Install postgreSQL

# tar xvfz postgresql-9.2.24.tar.gz # cd postgresql-9.2.24 # ./configure # make # make install

PostgreSQL Installation Issue:

You may encounter the following error message while performing ./configure during postgreSQL installation.

# ./configure checking for -lreadline... no checking for -ledit... no configure: error: readline library not found If you have readline already installed, see config.log for details on the failure.  It is possible the compiler isn't looking in the proper directory. Use --without-readline to disable readline support.

PostgreSQL Installation Solution:

Install the readline-devel and libtermcap-devel to solve the above issue.

# yum install libtermcap-devel readline-devel

Step 3: Verify the postgreSQL directory structure

After the installation, make sure bin, doc, include, lib, man and share directories are created under the default /usr/local/pgsql directory as shown below.

# ls -l /usr/local/pgsql/ total 14 drwxr-xr-x 2 root root 4096 Jan 22 10:24 bin lrwxrwxrwx 1 root root 4096 Jan 22 14:17 data drwxr-xr-x 6 root root 4096 Jan 22 10:24 include drwxr-xr-x 3 root root 4096 Jan 22 10:24 lib drwxr-xr-x 6 root root 4096 Jan 22 13:28 share

Step 4: Create postgreSQL user account

# adduser postgres # passwd postgres Changing password for user postgres. New UNIX password: Retype new UNIX password: passwd: all authentication tokens updated successfully.

Step 5: Create postgreSQL data directory

Create the postgres data directory and make postgres user as the owner.

# mkdir /usr/local/pgsql/data # chown postgres:postgres /usr/local/pgsql/data # ls -ld /usr/local/pgsql/data drwxr-xr-x 2 postgres postgres 19 Jan 22 14:17 /home/postgres/data

Step 6: Initialize postgreSQL data directory

Before you can start creating any postgreSQL database, the empty data directory created in the above step should be initialized using the initdb command as shown below.

# su - postgres # /usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data/

Step 7: Validate the postgreSQL data directory

Make sure all postgres DB configuration files (For example, postgresql.conf) are created under the data directory as shown below.

$ ls -l /usr/local/pgsql/data total 60 drwx------ 7 postgres postgres    67 Jan 22 14:23 base drwx------ 2 postgres postgres  4096 Jan 22 14:25 global drwx------ 2 postgres postgres    18 Jan 22 14:23 pg_clog -rw------- 1 postgres postgres  4302 Jan 22 14:23 pg_hba.conf -rw------- 1 postgres postgres  4476 Jan 22 14:23 pg_hba.conf-default -rw------- 1 postgres postgres  1636 Jan 22 14:23 pg_ident.conf drwx------ 4 postgres postgres    36 Jan 22 14:23 pg_multixact drwx------ 2 postgres postgres    18 Jan 22 14:24 pg_notify drwx------ 2 postgres postgres     6 Jan 22 14:23 pg_serial drwx------ 2 postgres postgres     6 Jan 22 14:23 pg_snapshots drwx------ 2 postgres postgres    25 Jan 22 16:09 pg_stat_tmp drwx------ 2 postgres postgres    18 Jan 22 14:23 pg_subtrans drwx------ 2 postgres postgres     6 Jan 22 14:23 pg_tblspc drwx------ 2 postgres postgres     6 Jan 22 14:23 pg_twophase -rw------- 1 postgres postgres     4 Jan 22 14:23 PG_VERSION drwx------ 3 postgres postgres    60 Jan 22 14:23 pg_xlog -rw------- 1 postgres postgres 19691 Jan 22 14:23 postgresql.conf -rw------- 1 postgres postgres    59 Jan 22 14:24 postmaster.opts -rw------- 1 postgres postgres    70 Jan 22 14:24 postmaster.pid -rw------- 1 postgres postgres   940 Jan 22 14:23 startup.log

Step 8: Start postgreSQL database

Use the postgres postmaster command to start the postgreSQL server in the background as shown below.

$ /usr/local/pgsql/bin/postmaster -D /usr/local/pgsql/data >logfile 2>&1 & [1] 2222 $ cat logfile LOG:  database system was shut down at 2020-01-22 11:10:10 WIB LOG:  database system is ready to accept connections LOG:  autovacuum launcher started

Step 9: Create postgreSQL DB and test the installation

Create a test database and connect to it to make sure the installation was successful as shown below

$ /usr/local/pgsql/bin/createdb test $ /usr/local/pgsql/bin/psql test Welcome to psql 9.2.24, the PostgreSQL interactive terminal. Type:  \copyright for distribution terms        \h for help with SQL commands        \? for help with psql commands        \g or terminate with semicolon to execute query        \q to quit test=#

Step 10:Enable remote access to PostgreSQL server

By default, the PostgreSQL server listens only on the local interface 127.0.0.1.
To enable remote access to your PostgreSQL server open the configuration file postgresql.conf and add listen_addresses = '*'
in the CONNECTIONS AND AUTHENTICATION section.

$ sudo vim /usr/local/pgsql/data/postgresql.conf

Edit like below

#------------------------------------------------------------------------------ # CONNECTIONS AND AUTHENTICATION #------------------------------------------------------------------------------ # - Connection Settings - listen_addresses = '*'     # what IP address(es) to listen on; port = 5432

$ sudo vim /usr/local/pgsql/data/pg_hba.conf

Edit like below

# TYPE  DATABASE        USER            ADDRESS                 METHOD # "local" is for Unix domain socket connections only local   all             all                                     md5 # IPv4 local connections: host    all             all             127.0.0.1/32            ident # IPv6 local connections: host    all             all             ::1/128                 ident # Allow replication connections from localhost, by a user with the # replication privilege. local   replication     all                                     peer host    replication     all             127.0.0.1/32            ident host    replication     all             ::1/128                 ident host    all             all             0.0.0.0/0               md5

save the file and restart the PostgreSQL service with:

$ sudo systemctl restart postgresql

Verify the changes with the ss utility or netstat

$ ss -nlt | grep 5432 LISTEN   0         128                 0.0.0.0:5432             0.0.0.0:* LISTEN   0         128                    [::]:5432                [::]:*

or you can use netstat

# netstat -pltnu | grep 5432 tcp        0      0 0.0.0.0:5432            0.0.0.0:*               LISTEN      5360/postmaster

As you can see from the output above the PostgreSQL server is listening on all interfaces (0.0.0.0).

and the last open port 5432

firewall-cmd --zone=public --add-port=5422/tcp firewall-cmd --zone=public --add-port=5422/tcp --permanent systemctl restart firewalld

Value '0000-00-00' can not be represented as java.sql.Timestamp IN PENTAHO (PDI)

In Kettle (Pentaho Data Integration), when you use a "Table Input" component, you have to create a database connection.
In the database connection form, fill the fields of your mysql database, and test it.
If successfull, go to Options (left tab)
In the right tab, below defaultFetchSize and useCursorFetch, add zeroDateTimeBehavior and it's value convertToNull

Hope this helps !

How do you create a read only user in postgresql

Grant usage/select to a single table

If you only grant CONNECT to a database, the user can connect but has no other privileges. You have to grant USAGE on namespaces (schemas) and SELECT on tables and views individually like so:

GRANT CONNECT ON DATABASE postgres TO user1; GRANT USAGE ON SCHEMA public TO user1; GRANT SELECT ON table01 TO user1;

Multiple tables/views

you can grant permissions on all tables/views/etc in the schema using a single command rather than having to type them one by one:

GRANT SELECT ON ALL TABLES IN SCHEMA public TO user1;

This only affects tables that have already been created. More powerfully, you can automatically have default roles assigned to new objects in future:

ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO user1;

Or you can create role before creating a user, like i usually do

-- Create a group CREATE ROLE read_access_dwh; -- Grant access to existing tables GRANT USAGE ON SCHEMA dwh TO read_access_dwh; GRANT SELECT ON ALL TABLES IN SCHEMA dwh TO read_access_dwh; -- Grant access to future tables ALTER DEFAULT PRIVILEGES IN SCHEMA dwhp GRANT SELECT ON TABLES TO read_access_dwh; -- Create a final user with password CREATE USER report_dwh WITH PASSWORD 'yourpassword'; GRANT CONNECT ON DATABASE postgres TO report_dwh; GRANT read_access_dwh TO report_dwh;

Postgres Command Line Connection from shell

This article describes how to connect to a PostgreSQL database from the shell using the psql program.
You can use the psql program as a quick and easy way to access your databases directly.


PSQL Commands: Connect to PostgreSQL from shell

To connect to PostgreSQL cli:

1. login to the server with SSH where the postgres database is located.


2. At the shell, type the following command. Replace DBNAME with the name of the database, and USERNAME with the database username:
   
   

   psql DBNAME USERNAME



3. At the Password prompt, type the database user's password. When you type the correct password, the psql prompt appears.


4. After you access a PostgreSQL database, you can run SQL queries and more. Here are some common psql commands:


• To view help for psql commands, type \?.
• To view help for SQL commands, type \h.
• To view information about the current database connection, type \conninfo.
• To list the database's tables and their respective owners, type \dt.
• To list all of the tables, views, and sequences in the database, type \z.
• To exit the psql program, type \q.

How to install SubversionEdge or CollabNet SVN on Centos

For any company in IT Department, versioning is a darn important part of the development process.

Software versioning is important because:

• It maintains the history of your code and the sequence in which changes were made
• It maintains the latest copy of your code in case your computer crashes
• It helps manage code properly when collaborating with other developers

You’ll understand the importance right away, when a developer you’re working with makes and edit that can’t be reverted or when a client accidentally deletes a file.
Trust me that happens.

In this article, I’m going to talk about installing this very software on Centos


Installing SubversionEdge

because we will install CSVN in user mode, for that we must create CSVN user first.

[root@localhost ~]# adduser csvn [root@localhost ~]# passwd csvn Changing password for user csvn. New password: Retype new password: passwd: all authentication tokens updated successfully.

Step #1 The Prerequisites

So, we start with the prerequisites. The prerequisite for SubversionEdge is Java. Hence, to begin with, we’ll have to install Java.
Now, if you’re not sure if Java is already installed, you can fire the below command to check the same:

[root@localhost ~]# java -version openjdk version "1.8.0_121" OpenJDK Runtime Environment (build 1.8.0_121-b13) OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode)

If Java is installed the Java version should be displayed. if java is not installed on your system, you can install java in the following url:


Step #2 Installing CollabNet SVN

Download the latest version of Subversion Edge from CollabNet. It should be a tar.gz file.

Then, use the below commands to install the software. Do remember to replace CollabNetSubversionEdge-5.2.4_linux-x86_64.tar.gz with the tar.gz file you’ve downloaded from CollabNet. and put the downloaded file into the folder /home

[root@localhost ~]# cd /home [root@localhost home]# [root@localhost home]# gzip -d CollabNetSubversionEdge-5.2.4_linux-x86_64.tar.gz [root@localhost home]# tar xf CollabNetSubversionEdge-5.2.4_linux-x86_64.tar [root@localhost home]# cd /home/csvn/bin/ [root@localhost bin]# ./csvn install Detected RHEL or Fedora: Installing the CSVN Console daemon.. Setting RUN_AS_USER to: 'root'. Please edit '../data/conf/csvn.conf' if this needs to be adjusted Setting JAVA_HOME to: ''. Please edit '../data/conf/csvn.conf' if this needs to be adjusted. [root@localhost bin]# ./csvn-httpd install Detected RHEL or Fedora:  Installing the Subversion Edge Apache Server daemon.. [root@localhost bin]# cd /home/ [root@localhost home]# chown csvn:csvn csvn/ -Rf

login as csvn user and edit file csvn.conf

[csvn@localhost ~]$ vi data/conf/csvn.conf

Setting RUN_AS_USER to: csvn

and back to root account again

CollabNet SVN should now be installed. All we need to do, is start their console and start using the application.
To start their console, fire the command

[root@localhost ~]# service csvn start Starting CSVN Console... ... CSVN Console started Waiting for application to initialize (this may take a minute)............................... CSVN Console is ready at http://localhost:3343/csvn

Once this command runs successfully, you can view CollabNet SVN at work by heading over to http://localhost:3343/csvn
That’s it! Hope you’ve got the service up and running. and you can adjust the server settings to the existing conditions


Good luck managing your repositories!

Install Java on Centos

INSTALL JAVA 

Download the latest JAVA  from  here or use the following command to download JAVA JDK

# wget --no-cookies \ --no-check-certificate \ --header "Cookie: oraclelicense=accept-securebackup-cookie" \ "https://download.oracle.com/otn-pub/java/jdk/8u201-b09/42970487e3af4f5aa5bca3f542482c60/jdk-8u201-linux-x64.rpm" \ -O /tmp/jdk-8u201-linux-x64.rpm

once the JAVA package has been downloaded, install it using rpm as follows:

# rpm -Uvh /tmp/jdk-8u201-linux-x64.rpm

CONFIGURE JAVA

configure the newly installed JAVA package using alternatives as in:

# alternatives --install /usr/bin/java java /usr/java/jdk1.8.0_201-amd64/jre/bin/java 20000 # alternatives --install /usr/bin/jar jar /usr/java/jdk1.8.0_201-amd64/bin/jar 20000 # alternatives --install /usr/bin/javac javac /usr/java/jdk1.8.0_201-amd64/bin/javac 20000 # alternatives --install /usr/bin/javaws javaws /usr/java/jdk1.8.0_201-amd64/jre/bin/javaws 20000 # alternatives --set java /usr/java/jdk1.8.0_201-amd64/jre/bin/java # alternatives --set javaws /usr/java/jdk1.8.0_201-amd64/jre/bin/javaws # alternatives --set javac /usr/java/jdk1.8.0_201-amd64/bin/javac # alternatives --set jar /usr/java/jdk1.8.0_201-amd64/bin/jar

check the JAVA version running on your system:

# java -version

Fix ORA-03113: end-of-file on communication channel

One day my server died suddenly due to a power problem, this caused a problem with my Oracle database,
ORA-03113: end-of-file on communication channel.

[oracle@localhost ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.4.0 Production on Fri Aug 16 14:22:01 2019 Copyright (c) 1982, 2013, Oracle.  All rights reserved. Connected to an idle instance. SQL> startup ORACLE instance started. Total System Global Area 4993982464 bytes Fixed Size            2261808 bytes Variable Size         1006636240 bytes Database Buffers     3976200192 bytes Redo Buffers            8884224 bytes Database mounted. ORA-03113: end-of-file on communication channel Process ID: 4903 Session ID: 237 Serial number: 26032

After searching for ways to repair the server, I finally found the solution. Here are the steps:

[oracle@localhost ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.4.0 Production on Fri Aug 16 14:22:01 2019 Copyright (c) 1982, 2013, Oracle.  All rights reserved. Connected to an idle instance. SQL> startup mount; ORACLE instance started. Total System Global Area 4993982464 bytes Fixed Size            2261808 bytes Variable Size         1006636240 bytes Database Buffers     3976200192 bytes Redo Buffers            8884224 bytes Database mounted. SQL> SELECT GROUP# FROM V$LOG;     GROUP# ----------      1      3      2 SQL> alter database clear unarchived logfile group 1; Database altered. SQL> alter database clear unarchived logfile group 2; Database altered. SQL> alter database clear unarchived logfile group 3; Database altered. SQL> shutdown immediate; ORA-01109: database not open Database dismounted. ORACLE instance shut down. SQL> startup ORACLE instance started. Total System Global Area 4993982464 bytes Fixed Size            2261808 bytes Variable Size         1006636240 bytes Database Buffers     3976200192 bytes Redo Buffers            8884224 bytes Database mounted. Database opened. SQL>

If this method still fails, then there is a second method, which is as follows
Now, go into sqlplus without opening the database, just mounting it.

[oracle@localhost ~]$ sqlplus /nolog SQL*Plus: Release 11.2.0.4.0 Production on Fri Aug 16 14:45:09 2019 Copyright (c) 1982, 2013, Oracle.  All rights reserved. SQL> connect / as sysdba Connected to an idle instance. SQL> startup mount ORACLE instance started. Total System Global Area 4993982464 bytes Fixed Size            2261808 bytes Variable Size         1006636240 bytes Database Buffers     3976200192 bytes Redo Buffers            8884224 bytes Database mounted. SQL>

Now, you can increase your current db_recovery_file_dest_size, increased to 100G in my case:

SQL> alter system set db_recovery_file_dest_size = 100G scope=both; System altered.

Now, you can shutdown and startup again and that previous error should be gone. The proper fix is to get rid of the recovery files. You do that using RMAN

[oracle@localhost ~]$ rman target / Recovery Manager: Release 11.2.0.4.0 - Production on Fri Aug 16 14:49:39 2019 Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved. connected to target database: DB11G (DBID=432722608, not open) RMAN> backup archivelog all delete input; Starting backup at 16-AUG-19 using target database control file instead of recovery catalog allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=156 device type=DISK specification does not match any archived log in the repository backup cancelled because there are no files to backup Finished backup at 16-AUG-19 RMAN> exit Recovery Manager complete.

Wait a long time and your archivelog (that was using up all that space) will be gone. So, you can shutdown/startup your database and be back in business.

[oracle@jktdi009 ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.4.0 Production on Fri Aug 16 14:52:16 2019 Copyright (c) 1982, 2013, Oracle.  All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> shutdown immediate; ORA-01109: database not open Database dismounted. ORACLE instance shut down. SQL> startup ORACLE instance started. Total System Global Area 4993982464 bytes Fixed Size            2261808 bytes Variable Size         1006636240 bytes Database Buffers     3976200192 bytes Redo Buffers            8884224 bytes Database mounted. Database opened. SQL>

vsftpd configuration of the ftp server in my company

Just to remember the vsftpd configuration of the ftp server in my company

The following configuration is on centos 6

anonymous_enable=NO local_enable=YES write_enable=YES local_umask=022 dirmessage_enable=YES xferlog_enable=YES xferlog_file=/var/log/vsftpd.log log_ftp_protocol=YES connect_from_port_20=YES xferlog_std_format=YES nopriv_user=ftp pam_service_name=vsftpd listen=YES tcp_wrappers=YES pasv_enable=YES pasv_max_port=1200 pasv_min_port=1026 port_enable=YES ascii_upload_enable=YES ascii_download_enable=YES ftpd_banner=Welcome to Private FTP Server. secure_chroot_dir=/home one_process_model=NO chroot_local_user=YES allow_writeable_chroot=YES guest_enable=NO use_localtime=YES #rsa_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem #rsa_private_key_file=/etc/ssl/private/ssl-cert-snakeoil.key seccomp_sandbox=NO

This works since 2011 after upgrading from Centos 5

If there are ORA-01092 and ORA-30012 errors together

Errors like this

ORA-01092: ORACLE instance terminated. Disconnection forced
ORA-30012: undo tablespace 'UNDOTBS01' does not exist or of wrong type

if there are ORA-01092 and ORA-30012 errors together, here's how to resolve them

[oracle@localhost ~]$ sqlplus /nolog SQL*Plus: Release 11.2.0.3.0 Production on Mon Aug 5 10:23:32 2019 Copyright (c) 1982, 2011, Oracle.  All rights reserved. SQL> connect sys as sysdba Enter password: Connected to an idle instance. SQL>

SQL> startup mount ORACLE instance started. Total System Global Area 535662592 bytes Fixed Size 1375792 bytes Variable Size 331350480 bytes Database Buffers 197132288 bytes Redo Buffers 5804032 bytes Database mounted.

SQL> select * from v$tablespace; TS# NAME INC BIG FLA ENC ---------- ------------------------------ --- --- --- --- 0 SYSTEM YES NO YES 1 SYSAUX YES NO YES 4 USERS YES NO YES 3 TEMP NO NO YES 6 EXAMPLE YES NO YES 9 RCRMAN YES NO YES 10 USERS_TBS YES NO YES 5 UNDOTBS2 YES NO YES 19 TESTTBS YES NO YES 14 TESTTB YES NO YES TS# NAME INC BIG FLA ENC ---------- ------------------------------ --- --- --- --- 15 TESTDB YES NO YES 12 rows selected.

SQL> create pfile='/oracle/product/11.2.0/db_1/dbs/initbckorcl.ora' from spfile; File created.

SQL> shutdown immediate ORA-01109: database not open Database dismounted. ORACLE instance shut down.

Edit Pfile UNDO_TABLESPACE PARAMETER

ORCL.undo_tablespace='UNDOTBS01' orcl.undo_tablespace='UNDOTBS01' *.undo_tablespace='UNDOTBS02'

Change like this

ORCL.undo_tablespace='UNDOTBS02' orcl.undo_tablespace='UNDOTBS02' *.undo_tablespace='UNDOTBS02'

Startup with new pfile

SQL> startup pfile='/oracle/product/11.2.0/db_1/dbs/initbckorcl.ora'; ORACLE instance started. Total System Global Area 535662592 bytes Fixed Size 1375792 bytes Variable Size 331350480 bytes Database Buffers 197132288 bytes Redo Buffers 5804032 bytes Database mounted. Database opened. SQL>

SQL> create spfile from pfile; File created. SQL> create spfile from pfile='/oracle/product/11.2.0/db_1/dbs/initbckorcl.ora'; File created.

SQL> shutdown immediate Database closed. Database dismounted. ORACLE instance shut down.

SQL> startup ORACLE instance started. Total System Global Area 535662592 bytes Fixed Size 1375792 bytes Variable Size 331350480 bytes Database Buffers 197132288 bytes Redo Buffers 5804032 bytes Database mounted. Database opened.

SQL> show parameter undo; NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ undo_management string AUTO undo_retention integer 900 undo_tablespace string UNDOTBS2

How to Install Nginx on CentOS 7

How to Install Nginx on CentOS 7

Nginx [engine x] is free and open source high-performance web server. It also acts as a reverse proxy server, as well as. This page shows how to install Nginx server on a CentOS 7 or RHEL 7 and configure a static web site.

In this article, we will explain how to install, configure and manage Nginx HTTP web server on a CentOS 7 or RHEL 7 server using command line.


Install Nginx Web Server

1. First update the system software packages to the latest version.



# yum -y update



2. Next, install Nginx HTTP server from the EPEL repository using the YUM package manager, or if you have not installed the epel repository you can install the nginx repository.

Configure EPEL repo



# yum install epel-release


Configure Nginx repo for CentOS 7 & RHEL (Red Hat Enterprise Linux) version 7.x



# vi /etc/yum.repos.d/nginx.repo


Append following for CentOS 7.x:



[nginx] name=nginx repo baseurl=http://nginx.org/packages/mainline/centos/7/$basearch/ gpgcheck=0 enabled=1


Append following for RHEL (Red Hat Enterprise Linux) version 7.x:



[nginx] name=nginx repo baseurl=http://nginx.org/packages/mainline/rhel/7/$basearch/ gpgcheck=0 enabled=1


Next, install Nginx



# yum install nginx

Manage Nginx HTTP Server

1. Once Nginx web server installed, you can start it first time and enable it to start automatically at system boot.



# systemctl start nginx # systemctl enable nginx # systemctl status nginx

Configure firewalld to Allow Nginx Traffic

1. By default, CentOS 7 and RHEL 7 built-in firewall is set to block Nginx traffic. To allow web traffic on Nginx, update the system firewall rules to permit inbound packets on HTTP and HTTPS using the commands below.



# firewall-cmd --zone=public --permanent --add-service=http # firewall-cmd --zone=public --permanent --add-service=https # firewall-cmd --reload

Test Nginx Server on CentOS 7 and RHEL 7

1. Now you can verify Nginx server by going to the following URL, a default nginx page will be shown.



http://SERVER_DOMAIN_NAME_OR_IP


You can also use the curl command to get same info using the cli:



$ curl -I http://10.21.136.13 $ curl http://10.21.136.13

Nginx Important Files and Directories

• The default server root directory (top level directory containing configuration files): /etc/nginx.
• The main Nginx configuration file: /etc/nginx/nginx.conf.
• Server block (virtual hosts) configurations can be added in: /etc/nginx/conf.d.
• The default server document root directory (contains web files): /usr/share/nginx/html.

Changing DNS Search Order

 

/etc/nsswitch.conf

Open /etc/nsswitch.conf file using text editor:

# vi /etc/nsswitch.conf

Look for hosts:

hosts: files dns mdns4

Set above order as per your requirement. Close and save the file.

host.conf – resolver configuration file

The file /etc/host.conf contains configuration information specific to the resolver library. It should contain one configuration keyword per line, followed by appropriate configuration information.

Open /etc/host.conf file

# vi /etc/host.conf

Find order line which specifies how host lookups are to be performed. It should be followed by one or more lookup methods, separated by commas. Valid methods are bind (dns server), hosts (/etc/hosts file), and nis (old method).

order hosts,bind

Save and close the file.

conclusion

 

The file /etc/nsswitch.conf will let you reconfigure the order of the name resolution. By default, the host file is the first, then the configured DNS. There could be more options.

The file /etc/hosts only lists IP addresses and hostnames (multiple names for one IP if you want) The file /etc/resolv.conf will list the default search domains, and will also list in sequence the name servers to use.