Firewalld

How to Resolve TNS-12535: TNS:operation timed out

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TNS-12535 Let’s see how we reproduce TNS-12535. C:\Users\ed>tnsping compdb TNS Ping Utility for 64-bit Windows: Version 12.1.0.1.0 – Production on 22-JUL-2014 19:03:21 Copyright (c) 1997, 2013, Oracle.  All rights reserved. Used parameter files: C:\oracle\app\client\ed\product\12.1.0\client_1\network\admin\sqlnet.ora Used TNSNAMES adapter to resolve the alias Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = primary01)(PORT = 1521)) […]
Linux

How to Change Primary Group of a User in Linux

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Change Primary Group In our case, there’s a user called oracle who has identification like following: [root@test ~]# id oracle uid=54321(oracle) gid=54321(oinstall) groups=54321(oinstall),54322(dba) I would like to change the primary group to dba and let oinstall join the secondary group. That is to say, my purpose is to switch the places of dba and oinstall. […]
Linux

How to Build 18c RAC – 1 of 4 – Preparing Two Database Servers

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Network Design for RAC Let’s see the network design of our cluster database. [root@primary01 ~]# vi /etc/hosts # Public 192.168.10.11 primary01 primary01.example.com 192.168.10.12 primary02 primary02.example.com # Private 192.168.24.11 primary01-priv primary01-priv.example.com 192.168.24.12 primary02-priv primary02-priv.example.com # VIP 192.168.10.111 primary01-vip primary01-vip.example.com 192.168.10.112 primary02-vip primary02-vip.example.com # SCAN # 192.168.10.81 primary-cluster-scan primary-cluster-scan.example.com # 192.168.10.82 primary-cluster-scan primary-cluster-scan.example.com # 192.168.10.83 primary-cluster-scan primary-cluster-scan.example.com […]
Linux

How to Resolve Configure: Error: no acceptable C compiler found in $PATH

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Python Installation Tried to install python 3.7.1 in Linux and met this error: “configure: error: no acceptable C compiler found in $PATH”. No doubt, this error will also appear in Ubuntu and CentOS. First of all, I downloaded the source from python official site, and then extract it. [root@test python]# curl -O https://www.python.org/ftp/python/3.7.1/Python-3.7.1.tgz   % […]
Apache

How to Resolve Too many open files AH00132: file permissions deny server access

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Saw some errors in httpd log:[Sat Jun 10 18:20:54.048569 2017] [core:error] [pid 5596] (24)Too many open files: [client 123.123.123.123:56399] AH00132: file permissions deny server access: /var/www/html/logo.png, referer: http://logic.edchen.org/Check the resource limit on open files. This includes hard limit and soft limit.[root@test ~]# ulimit -H -n4096[root@test ~]# ulimit -S -n1024It could be too small to support […]
Apache

How to Make httpd.conf Take Effect Without Restart

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Since restarting httpd service may cause connections disrupted for seconds, you may use reload action instead of restart to make your httpd server apply new configuration in httpd.conf without interrupt online connections.In EL6, you can use this command:[root@test ~]# service httpd reloadIn EL7, you can use this command:[root@test ~]# systemctl reload httpd
Linux

How to Migrate Local Databases to Remote Host or Vice Versa Without Dump Files

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For migrating a remote database, you can dump and pipe the whole database from remote server to local server via ssh tunnel without intermediate dump files.[root@test ~]# ssh 10.10.10.1 “mysqldump –routines -u root -p’xxxxxxxx’ chicago_db” | mysql -u root -p’xxxxxxxx’ -D boston_dbVice versa, you can migrate a local database to the remote server.[root@test ~]# mysqldump […]
Linux

How to Mount an Uploaded ISO file in Linux

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If you were limited to access /dev/cdrom, you can still utilize the content of an ISO by uploading and mounting it. The syntax is as the following:mount -o ro,loop <source_path> <target_path>For example, we can mount an uploaded ISO file as a media like this:[root@ovmm ~]# mount -o ro,loop /tmp/ovmm-3.4.2-installer-OracleLinux-b1384.iso /media[root@ovmm ~]# ll /mediatotal 157557drwxr-xr-x. 7 […]
Linux

How to Set Date Time of Linux OS Manually

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Sometimes, you can’t use NTP to adjust your server time, you can change it by a command line.[root@rac1 ~]# date -s ‘2017-02-18 17:30:00’Sat Feb 30 17:30:00 CST 2017The option “s” is set the time by its following string.[root@rac1 ~]# dateSat Feb 30 17:30:12 CST 2017Chances are, you may need to change a bunch of server […]
bash

How to Increase Bash History Size

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Some valuable or complex commands may not be able to keep in your mind constantly when you need them. In this moment, you can leverage the command history to recall them. But as time goes by, you could lose them due to the size limitation of command history. The history always keep the most recent […]