Find common/identical lines within two files without DIFF

Here is really simple trick how to search for strings that are the same within two different files.

For presenting purposes I created two files with some text in it. Some text is the same, some not.

File 1:

> $ cat file1.txt 
test1
test2
test3
test4
test5

File2:

> $ cat file2.txt 
lala1
lala2
test3
test4
lala4
lala6

Here is how to find strings that are the same within both files:

> $ cat file1.txt file2.txt | sort | uniq -c | grep "2 " 
2 test3
2 test4

So, strings test3 and test4 occurring in both files.

Nice way to do HTTP to HTTPS redirection with Apache .htaccess

I had some sites on shared hosting environment for which I had to do http to https redirection with .htaccess file. I did 302 redirection intentionally so that in case of error, browser doesn’t cache redirection. You can aslo make permanent 301 redirect if needed.

This is nice and simple way to do it:

RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=302]

Moodle – mysql/mariadb Antelope to Barracuda installation warning

I tried to install Moodle 3.5.2 on cPanel server and got this warning in installation process:

“Your database has tables using Antelope as the file format. You are recommended to convert the tables to the Barracuda file format. See the documentation Administration via command line for details of a tool for converting InnoDB tables to Barracuda.”

Because this was production hosting server, I was unable to just globally change mysql settings. To be able to proceed installation, open config.php file of your moodle and change variable dbcollation like this:

dbcollation' => 'utf8_unicode_ci'

Multidomain webroot for Letsencrypt with NGINX

If you have web server on which there is a lot of virtual hosts, you may want to have one webroot directory for Letsencrypt SSL certificates only. So when Letsencrypt will make the requests for SSL registration or renewal, it will look in this directory. In this case I did this on CentOS 7 with NGINX web server.

First, let’s create directory what will be used for letsencrypt purposes. It must be writable by your web server user. You can define different path.

[root@machine ~]# mkdir -p /var/www/le-certs
[root@machine ~]# chown -R wwwuser:wwwgroup /var/www/le-certs

Letsencrypt will need access in “.well-known/acme-challenge”. For NGINX add something like this in your server block for desired virtual host.

location ~ /.well-known/acme-challenge/ {
             root /var/www/le-certs/;
             break;
}

You can also create new file named, for example le-config.conf and add block above in to it. Then you can simply include this line in your virtual hosts. 

server {
             listen :443 ssl http2;
             server_name mywebsite.com www.mywebsite.com;
             root /var/www/mywebsite/;

             include le-config.conf;
              ...
}

 

 

WordPress returning 404 Error on all subpages

In this case I used NGINX as reverse proxy for ssl offloading in front of Apache. On this WordPress installation I was getting 404 on all subpages. Htaccess syntax was correct as it was nginx configuration. In this case, problem was caused because of missing “AllowOverride” Apache directive which didn’t allow htaccess to be processed. I added “AllowOverride ALL” in apache configuration for this virtual host. Subpages started to work.

Example:

<VirtualHost *:8080>
DocumentRoot /var/www/mysite.com/
ServerName mysite.com
ServerAlias www.mysite.com

<Directory "/var/www/mysite.com/">
AllowOverride All
</Directory>
</VirtualHost>

WordPress: Too Many Redirects Issue when NGINX reverse proxy to Apache

I installed NGINX and put it in front of Apache for SSL offloading and caching static content. Traffic is proxied from Nginx to Apache.  When I tried to open site via https, it returned this painful error “Too Many Redirects”.

Try to add this in your wp-config.php – if you have everything else configured correctly, it should work:

$_SERVER['HTTPS'] = 'On';

MySQL/MariaDB – [ERROR] Plugin InnoDB registration as a STORAGE ENGINE failed error

I was migrating server and rsync all databases to new mariadb server. When tried to start mariadb on new server, I was getting this error:

Apr 24 18:30:26 my.server.com mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [ERROR] Plugin 'InnoDB' init function returned error.
Apr 24 18:30:26 my.server.com mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
Apr 24 18:30:26 my.server.com mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [Note] Plugin 'FEEDBACK' is disabled.
Apr 24 18:30:26 my.server.com mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [ERROR] Unknown/unsupported storage engine: InnoDB
Apr 24 18:30:26 my.server.com mysqld[9703]: 2018-04-24 18:30:26 140298644924544 [ERROR] Aborting

Solution is to generate new ib_logfile0 and ib_logfile1 files. Just try steps bellow.

[root@lol ~]# cd /var/lib/mysql
[root@lol mysql]# mv ib_logfile0 ib_logfile0-backup 
[root@lol mysql]# mv ib_logfile1 ib_logfile1-backup
[root@lol mysql]# systemctl start mysql
[root@lol mysql]# mysql
Welcome to the MariaDB monitor.

It should work.

Linux: restore all system permissions of your server

If you ever found your self in situation when you accidentally overwrite all permissions of your system, and everything stops working, then solution bellow may do the trick. This CentOS server was overwritten by wrong permissions through the whole system. Quick solution is to set up right permissions back. If you have backup of server that’s great. Otherwise you’ll have to set up new server with similar installation or do this on some other server with similar installation.

On “new” server, copy permissions of the whole system and save it to a file. You can also exclude dirs that you don’t need also.

find / -not -path "/proc*" -not -path "/dev*" -not -path "/sys*" -not -path "/var/www*" -exec stat -c "chmod %a %n;" {} \; > permissions.txt

On your “broken” server, rewrite all permissions:

cat permissions.txt | bash

Create and password protect/encrypt zip archive from command line / stored 0% message

When sending zip archives that contains risky/secure content, you should always encrypt and password protect them. Especially when sending them to clients via email, Dropbox or some other public sharing method. To do that on Linux is very simple. You can do it with commands bellow. When executed you’ll be prompted to enter password.

When adding file, just do this:

zip --encrypt myarchive.zip myfile.txt

But when adding directory with subdirectorys and files, than you should always include “-r” flag to tell zip to use recursion. Otherwise you’ll end up with empty directory and see message like this “adding: behaviour.exchange/ (stored 0%)”

To add directory recursively:

zip --encrypt -r myarchive.zip mydir/

 

Update all php extensions at once with YUM

With YUM, upgrading php is simple as “yum install php”. This will install latest php version on your machine. But if you have multi different php modules that aren’t part of php package (eg. gd, mysqli …), than you can use this simple one liner and install all those modules at once.

Just run this as root:

php -m | grep -v "Modules" | while read i; do yum install php-$i -y; done

This will check for all currently installed php packages and will try to upgrade them.

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