AWS RDS - Create mysql user with superuser Privileges

Login as super user on command prompt.

Run following query to create user.

CREATE USER 'username'@'%' IDENTIFIED BY 'password';

Just change username and password in above query and execute as root user. A new user will be created.

Now give super user privileges to new user.

GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, RELOAD, PROCESS, REFERENCES, INDEX, ALTER, SHOW DATABASES, CREATE TEMPORARY TABLES, LOCK TABLES, EXECUTE, REPLICATION SLAVE, REPLICATION CLIENT, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE, CREATE USER, EVENT, TRIGGER ON *.* TO 'username'@'%' WITH GRANT OPTION;

Just change username in above query. Your new created user will be a super user now.

AWS RDS - Give Superuser Privileges to Regular mysql User

Login as super user on command prompt.

Run following query to give superuser privileges to normal user.

GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, RELOAD, PROCESS, REFERENCES, INDEX, ALTER, SHOW DATABASES, CREATE TEMPORARY TABLES, LOCK TABLES, EXECUTE, REPLICATION SLAVE, REPLICATION CLIENT, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE, CREATE USER, EVENT, TRIGGER ON *.* TO 'username'@'%' WITH GRANT OPTION;

Just change username in above query and execute as root user. Your regular user will be a super user now.

Wordpress Permissions - Upload plugin using wp-admin

Upload plugin using wp-admin without ftp.

If you are not able to install plugin using wp-admin because of forbidden error or a permission issue, you simply change the permission of whole wordpress directory to fix it. That is very dangerous and a common security loophole.

Here is the minimum permission for your plugin directory which is enough to instal plugin using wp-admin.

Give 777 to wp-content/plugins and wp-content/upgrade Non-Recursively. It will allow admin to install plugin using wp-admin.

postgresql error : ERROR: database is being accessed by other users

ERROR:  database "X" is being accessed by other users
DETAIL:  There is 1 other session using the database

Solution :

SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE pid <> pg_backend_pid() AND datname = 'database-name';

You need to replace only database name in above query.

Now you can drop the database or perform other activity what you were trying to perform.

composer update - exceeded the timeout of 300 seconds

Failed to download from source: The process  exceeded the timeout of 300 seconds.

Solution :
Increase the timeout limit globally for composer

composer --global config process-timeout 6000

Now run

composer update

You should not get timeout issue.

gitlab forbidden issue

This feature has been added by default in recent update of gitlab.
When there are number of failed login attempts while cloning or pushing files into gitlab repository, gitlab blocks UI as well as pull and push for the IP. Technically, it bans the IP.

Solution :
Disable this feature.

sudo nano /etc/gitlab/gitlab.rb

Uncomment these lines.

gitlab_rails['rack_attack_git_basic_auth'] = {
'enabled' => false,
}

Reconfigure gitlab.

sudo gitlab-ctl reconfigure

Now it will not block that ip after number of failed login attempts.

ubuntu 16.04 - wkhtmltopdf error - QSslSocket: cannot resolve CRYPTO_num_locks

wkhtmltopdf error on ubuntu 16.04 :
Loading pages (1/6)
QSslSocket: cannot resolve CRYPTO_num_locks                  ] 10%
QSslSocket: cannot resolve CRYPTO_set_id_callback
QSslSocket: cannot resolve CRYPTO_set_locking_callback
QSslSocket: cannot resolve sk_free
QSslSocket: cannot resolve sk_num

Solution :

sudo apt-get install libssl-dev=1.0.2g-1ubuntu4.10 openssl=1.0.2g-1ubuntu4

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

Ruby Error while installing charlock_holmes 

Error :
Fetching charlock_holmes 0.7.5
Installing charlock_holmes 0.7.5 with native extensions
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.


Solution : 1
If you are using debian or ubuntu

sudo apt-get install libicu-dev

If you are using Centos or fedora

sudo yum install libicu-devel

Solution : 2
Try to install other version of charlock_holmes

gem pristine charlock_holmes --version 0.6.9.4

or

gem install charlock_holmes -v '0.6.9'

Skipping ssh-dss key id_dsa - not in PubkeyAcceptedKeyTypes

SSH keeps skipping my pubkey and asking for a password

You have correct ssh key but still it is asking password to login or if password authentication is prohibited, it stopped accepting correct keys.

If it was working before and suddenly it starts giving above error, it means you have upgraded your openssh. The new openssh version - 7.0+ does not support DSA keys anymore  (Neither on server nor on client). 

If openssh client has been upgraded and openssh server still supports DSA keys, make the changes in client side ssh config.

Solution  :

sudo nano /etc/ssh/ssh_config

Add following line in the file.

PubkeyAcceptedKeyTypes=+ssh-dss

Restart ssh.

If openssh server has been upgraded and openssh client still supports DSA keys, make the changes in server side sshd config.

Solution  :

sudo nano /etc/ssh/sshd_config

Add following line in the file.

PubkeyAcceptedKeyTypes=+ssh-dss

Restart ssh.

Note :  The best solution, you must use RSA keys. It has strong and secure algorithm and it is better than the patch you are finding.

openedx installation on Linux | openedx installation on Ubuntu

Easy way :
1. Download the installer (.run file)

https://bitnami.com/stack/edx/installer

2. Make it executable.

chmod a+x filename.run

3. Run the installer.

./filename.run

Hard way:
Install using bash script. Why it is hard because it is gonna give many errors, you need to fix them one by one and start installing again and again until it is installed completely.

wget https://raw.githubusercontent.com/edx/configuration/$OPENEDX_RELEASE/util/install/sandbox.sh -O - | bash

You choose the version of Open edX by setting the OPENEDX_RELEASE variable before running the commands. See Open edX Releases for the tags you can use.

https://openedx.atlassian.net/wiki/spaces/DOC/pages/11108700/Open+edX+Releases

Release names like open-release/ginkgo.2, open-release/eucalyptus.3, open-release/ficus.4 etc

Example:

wget https://raw.githubusercontent.com/edx/configuration/open-release/ginkgo.2/util/install/sandbox.sh -O - | bash

Helpful url :

https://openedx.atlassian.net/wiki/spaces/OpenOPS/pages/146440579/Native+Open+edX+Ubuntu+16.04+64+bit+Installation

Hardest way:
Install each package separately like these guides are suggesting. Similar guides you can find for centos and fedora.

https://www.iblstudios.com/step-step-guide-install-open-edx-platform-ficus-release/

I would suggest you to install on virtual machine like docker, vagrant or vmware instead of start installing on your system.

postgresql - Check ip of logged in user

To get Logged in user IP

Run Query :

postgres=> select inet_client_addr();

mysql - Check IP of logged in user

Run Query :

mysql> select user();

Mysql 5.7 - Update root password

mysql 5.7 does not have password field in user table of mysql database. They have come up with new idea i.e. authentication_string for security purpose.

Here is way to update mysql superuser password using command line.

UPDATE mysql.user SET authentication_string=PASSWORD('sToituY78hebrt'), plugin='mysql_native_password' WHERE User='root' AND Host='localhost';

where sToituY78hebrt is my root password

Invalid command '\xef\xbb\xbf#', perhaps misspelled or defined by a module not included in the server configuration

\xef\xbb\xbf are three invisible junk characters (at least from Apache's perspective) called the Unicode BOM, or byte order mark. Apache thinks that those characters are part of the command that follows right after. This is what you see in the log, though the characters are escaped so they're visible to the naked eye. \xef\xbb\xbfRewriteEngine

Copy the content in any advanced notepad editor which will detect the characters and you can easily remove them.

If you are not able to see these characters, remove this file completely and write again.

cpanel - wordpress - internal server error because of invalid permissions

cpanel - wordpress application - fix wordpress permissions of complete directory

cpanel > wordpress tool kit > Manage your site (Click on manage button) > Fix Permissions

It will fix all permissions of wordpress directory.

s3cmd : Configure multiple s3 buckets of multiple aws accounts on same server

First configure s3 bucket of 'AWS account - A' with s3cmd

s3cmd --configure

Add Access key and Secret Key of your 'AWS account A'.

Now rename ~/.s3cfg to ~/.s3cfg-first

You can find .s3cfg file in your home directory of logged in user.

Now configure s3 bucket of 'AWS account - B'

s3cmd --configure

Add Access key and Secret Key of your 'AWS account B'.

Now rename ~/.s3cfg to ~/.s3cfg-second
 
Configure third and so on

If you do not define config file parameter in command, it takes default config file i.e. .s3cfg

You need to define config file with command and you can communicate with different s3 buckets of one AWS account or multiple AWS accounts.

s3cmd ls s3://bucketname -c ~/.s3cfg-first

Above command will list the content of the defined s3 bucket of AWS account - A.

s3cmd ls s3://bucketname -c ~/.s3cfg-second

Similarly it will list the content of the defined s3 bucket of AWS account - B.

Now you can copy content, delete content or move them with different s3cmd commands.

Note : Number of buckets you can access of AWS account A or AWS account B, it depends on the privileges provided to access key and secret key and privileges are defined by the policy attached to the user whose access key and secret key you are using. 

If a policy which has read, write and list access of only one bucket 'Bucket-A' of an AWS account and this is the only policy attached to a user whose access key and secret key you are using then you can access only Bucket-A of that AWS account by using the access key and secret key of the user.

Use Redirect and Proxypass under one virtualhost in apache

If you need to redirect your domain on another domain or you need to redirect http to https, you use Redirect Permanent in your virtualhost to achieve but if your application is running on different port (node, python, ruby etc) and you have resolved port using proxy pass then your redirect attribute might not be working.

To solve this issue, use redirect under proxy directive.

<VirtualHost *:80>
    ProxyPreserveHost On
    ProxyPass / http://localhost:8080/
    ProxyPassReverse / http://localhost:8080/
<Proxy *>
    Redirect permanent / https://domain.co.in
</Proxy>
</VirtualHost>

Now your port will be resolved with domain as well as you can redirect domain too.

/opt/lampp/bin/httpd: relocation error: .so: symbol SSL_library_init, version OPENSSL_1.0.0 not defined in file libssl.so.1.0.0 with link time reference

Xampp apache is not starting after adding stomp extension or mongo extension in php.ini file. After installation using pecl, you have added following line in php.ini file.
extension=mongo.so
extension=stomp.so

Now when you try to restart xampp, apache does not start. 

When you check the apache log, you see following error.

/opt/lampp/bin/httpd: relocation error: stomp.so: symbol SSL_library_init, version OPENSSL_1.0.0 not defined in file libssl.so.1.0.0 with link time reference

/opt/lampp/bin/httpd: relocation error: mongo.so: symbol SSL_library_init, version OPENSSL_1.0.0 not defined in file libssl.so.1.0.0 with link time reference

If you remove the extension line in php.ini, apache works fine but you need to use the extension so you can not remove it, here is the solution.

Solution :

Install stomp or mongo or other extension with disable ssl support

Choose no option while installing stomp/mongo/extension-name

OpenSSL install prefix (no to disable SSL support) [/usr] : no

Now when you add extension in php.ini, the apache works fine and you are able to use the installed extension.

XAMPP is currently only available as 32 bit application. Please use a 32 bit compatibility library for your system.

Solution - I
If you have latest 64 bit Linux Operating system like recent versions of Ubuntu / Debian / CentOS or Fedora and you want to use older version of php or mysql ( php 5.3 or php 5.4) then you should follow Solution - I.

Older libraries of xampp supports 32 bit operating system so your latest 64 bit operating system is not able to install older xampp.

To make it working install Ubuntu 12.04 LTS or Debian 7.0 in Vmware or Virtualbox
or 
Download ubuntu 12.04 docker image and install xampp inside it, it is faster solution and will not occupy too much RAM.

Solution - II

If your xampp was working fine and suddenly it has started giving this error then this solution is for you

Most common reason of this error, you have added an extension in xampp and after adding it in php.ini, the lampp is not getting started. You are getting following error :

XAMPP is currently only available as 32 bit application. Please use a 32 bit compatibility library for your system.

Here is the solution for you.

Comment following code in the file /opt/lampp/lampp

#case `uname -m` in
#    *_64)
#    if $XAMPP_ROOT/bin/php -v > /dev/null 2>&1
#    then
#        :
#    else
#        $GETTEXT -s "XAMPP is currently only availably as 32 bit application. Please use a 32 bit compatibility library for your system."
#        exit 1
#    fi
#    ;;
#esac

Now restart xampp and you should not get above error.

If still there is error and it was because of new installed extension, I would suggest to comment the extension .so line in php.ini and restart xampp.

You can see the solution in the following video.