Country block/allow with iptables and ipset

Here is a simple way to restrict access to your server from country’s that you don’t want to be able to connect to your services. On website you can find IP lists for specific country’s. With a simple script, you can regularly update those lists so that they are up-to-date with new addresses. In my case, I needed a way to allow some services only available from specific countries. You can also change logic a little bit and blocking only specific county. 

This will work on Linux server with installed iptables and ipset. Ipset will contain all addresses provided from 

First, if you don’t already have it, install ipset.

[root@server ~]# dnf install ipset

Then, you’ll need to create ipset array which will contain all addresses. 

ipset create allow_cc hash:net family inet hashsize 1024 maxelem 65536

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mysql_secure_installation: command not found

It’s always a good idea to do basic MySQL security measures after installing fresh version of MariaDB server. For this task, I always used “mysql_secure_installation” command, which was part of installation. Some time ago, I’ve got stucked when trying to do so on MariaDB version 10.7. After some searching around, I guess command was changed.

[root@server ~]# mysql_secure_installation
-bash: mysql_secure_installation: command not found

This is a correct way on newer MariaDB versions:

root@server ~]# mariadb-secure-installation
. . .


Find occurrences of the same string between two files with grep

I had this issue many times. Find the same occurrences of string between two different files so that you can pervent duplicates.

You should create foor loop that will take every line from file 1 and compare it to records in file 2.

for i in `file1.txt`; do grep -E "^$i\$" file2.txt; done

This will output only the exact strings that occurres in both files.

Letsencrypt/certbot fails when proxying with Apache ProxyPass

I had an issue on Directadmin server where client had nodejs application for which apache had to proxy on port 3001. Becouse of this, letsencrypt was not able to reach .well-known/acme-challenge/ and certificate registration/renewal failed. Solution is simple, you have to exclude proxy when requesting .well-known/acme-challenge/.

This was error whent trying to check .well-known/acme-challenge:

$ curl 
{"errors":[{"message":"Route /.well-known/test.txt doesn't exist.","extensions":{"code":"ROUTE_NOT_FOUND"}}]}%

So I added “ProxyPass !” directive just before where I create proxy directive to port 3001. Like so:

. . .
<Location /.well-known/acme-challenge>
   ProxyPass !

<Location />
Require all granted
. . . 

Then I was able tu make request to .well-known/acme-challenge sucsessfully:

> $ curl 
It works!

I hope this helps! 🙂

Dovecot fails to reload after upgrade / code=exited, status=226/NAMESPACE

If your Dovecot fails to reload/restart after upgrade, chances are that your kernel is too old. But you can try and fix this problem with simple step bellow.

This was in syslog log:

systemd[20406]: dovecot.service: Failed at step NAMESPACE spawning /usr/bin/doveadm: No such file or directory
dovecot.service: Control process exited, code=exited status=226
systemd[1]: Reload failed for Dovecot IMAP/POP3 email server.

This was Dovecot service status:

● dovecot.service - Dovecot IMAP/POP3 email server
Loaded: loaded (/lib/systemd/system/dovecot.service; enabled; vendor preset: enabled)
Active: active (running) (Result: exit-code) since Tue 2021-09-07 19:31:12 CEST; 1 months 28 days ago
Docs: man:dovecot(1)
Process: 20406 ExecReload=/usr/bin/doveadm reload (code=exited, status=226/NAMESPACE)

To solve, you can try and edit dovecot service script and add coment to PrivateTmp variable.

root@mailmachine:~# vi /lib/systemd/system/dovecot.service

ExecReload=/usr/bin/doveadm reload
ExecStop=/usr/bin/doveadm stop
# Enable this if your systemd is new enough to support it:

SNI support for Dovecot and Postfix

If you are in position that you need multiple SSL certificates for different domains on single mail server, you can do it with SNI. Of corse, on very old versions this is not supported. Check documentation first, if its supported for your version of Dovecot and Postfix.


In case of incoming mailserver Dovecot it’s easy as listed bellow. I made file ssl-sni.conf in which I add SNI configurations for my domains. Then I included ssl-sni.conf in main dovecot config.

Create ssl-sni.conf and add your SNI definitions in it:

local_name {
ssl_cert = </etc/ssl/certs/domain1/fullchain.pem
ssl_key = </etc/ssl/certs/domain1/privkey.pem

local_name {
ssl_cert = </etc/ssl/certs/domain2/fullchain.pem
ssl_key = </etc/ssl/certs/domain2/privkey.pem

Then include this in main dovecot config (you can add those configurations directly in dovecot.conf or 00-ssl.conf also. I just prefer separate this):

# SNI include
!include ssl-sni.conf


As for Postfix, configuration is also simple:

Inside /etc/postfix/, create file and add ssl definitions in it: /etc/ssl/certs/domain1/privkey.pem /etc/ssl/certs/domain1/fullchain.pem /etc/ssl/certs/domain2/privkey.pem /etc/ssl/certs/domain2/fullchain.pem

Run postmap and restart Postfix:

[root@mail postfix]# postmap -F which will create
[root@mail postfix]# systemctl restart postfix

If everything is OK, you should now have SNI supported mail server.

Directadmin – ModSecurity: Request body (Content-Length) is larger than the configured limit (13107200)

I had problem with uploading files on Directadmin server with mod_security enabled. I set upload_max_filesize and post_max_size to 64M, and still recived error like this:

[Wed Aug 04 23:31:30.320425 1912] [:error] [pid 1418987:tid 140666332325632] [client] [client] ModSecurity: Request body (Content-Length) is larger than the configured limit (13107200). [hostname ""] [uri "/wp-admin/async-upload.php"] [unique_id "YQpCUpEZgUlp9rxIlbunrAAAnTQ"], referer:

I found out that this behavior is not caused by any mod_security rules (Free ModSecurity Rules from Comodo) but by directive SecRequestBodyLimit setting . Default value is 12.5M and since I set 64M for file uploads, I changed this value the same – in bytes.

File which you want to modify is /etc/httpd/conf/extra/httpd-modsecurity.conf. In my case, I modifyed like this:

SecRequestBodyLimit 67108864
SecRequestBodyNoFilesLimit 1048576

Directadmin – get disk size information for every email account on your server/user

If you want to get information about how much of disk is consuming every email account on your Directadmin server, then you can use this command.

[root@post ~]# find /home/*/imap/*/*/ -maxdepth 1 -type d -exec du -sh {} \; | awk -F '/' {'print $6"@"$5 " -> " $1'} -> 60K -> 60K -> 529M -> 529M -> 772K

If you would want for every email account of some specific user, than you can use this:

[root@post ~]# find /home/user1/imap/*/*/ -maxdepth 1 -type d -exec du -sh {} \; | awk -F '/' {'print $6"@"$5 " -> " $1'} -> 1.3G -> 1.3G -> 68M

Simple, but it can save some time 🙂

Build NGINX with GeoIP2 support from source

I used GeoIP library with Nginx for quite some time, but it came to EOL. GeoIP2 is now avalible. It is great tool for blocking unwanted traffic from your webserver. This was done on Centos 7. If you don’t want to pay for getpagespeed’s payed version, than you must build this module from source.

First, you’ll need to know your curent NGINX version

[root@myserver ~]# nginx -v
nginx version: nginx/1.16.1

Then, download exact same version of NGINX from this site and unpack it. In my case:

[root@myserver ~]# wget
[root@myserver ~]# tar -xvzf nginx-1.16.1.tar.gz
[root@myserver ~]# cd nginx-1.16.1.tar.gz

Then you should download ngx_http_geoip2_module – geoip2 module for NGINX:

[root@myserver ~]# wget
[root@myserver ~]# unzip

You should install GCC and Development Tools for dependencies.

[root@myserver ~]# yum groupinstall ‘Development Tools’
[root@myserver ~]# yum install gcc

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