Category: Technology

Published on by Nayar

Upgrading from MySQL to MariaDB on Ubuntu Server 16.04LTS

Let’s see which version of MySQL is installed

root@mysql-bak:~# dpkg -l | grep mysql
ii  mysql-client-5.7                 5.7.22-0ubuntu0.16.04.1  
ii  mysql-client-core-5.7            5.7.22-0ubuntu0.16.04.1  
ii  mysql-common                     5.7.22-0ubuntu0.16.04.1
ii  mysql-server                     5.7.22-0ubuntu0.16.04.1 
ii  mysql-server-5.7                 5.7.22-0ubuntu0.16.04.1  
ii  mysql-server-core-5.7            5.7.22-0ubuntu0.16.04.1

Rumour says that MariaDB is a “drop-in” replacement for MySQL. Let’s try install MariaDB as is.

reimport them hereroot@mysql-bak:~# apt-get install mariadb-server
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following package was automatically installed and is no longer required:
  libevent-core-2.0-5
Use 'apt autoremove' to remove it.
The following additional packages will be installed:
  libdbd-mysql-perl libdbi-perl libmysqlclient20 libterm-readkey-perl mariadb-client-10.0 mariadb-client-core-10.0 mariadb-common mariadb-server-10.0 mariadb-server-core-10.0
Suggested packages:
  libclone-perl libmldbm-perl libnet-daemon-perl libsql-statement-reimport them hereperl mailx mariadb-test tinyca
The following packages will be REMOVED:
  mysql-client-5.7 mysql-client-core-5.7 mysql-server mysql-server-5.7 mysql-server-core-5.7
The following NEW packages will be installed:
  libdbd-mysql-perl libdbi-perl libmysqlclient20 libterm-readkey-perl mariadb-client-10.0 mariadb-client-core-10.0 mariadb-common mariadb-server mariadb-server-10.0 mariadb-server-core-10.0
0 upgraded, 10 newly installed, 5 to remove and 0 not upgraded.
Need to get 16.3 MB of archives.
After this operation, 15.2 MB disk space will be freed.
Do you want to continue? [Y/n]

And we press Y!

The old data directory will be saved at new location. │ │ A file named /var/lib/mysql/debian-*.flag exists on this system. The number indicated │ │ Therefore the previous data directory will be renamed to /var/lib/mysql-* and a new d │ │ Please manually export/import your data (e.g. with mysqldump) if needed.

And all your data is not accessible.

You’ll need to have MariaDB 10.1 or higher which can import MySQL data.

sudo apt-get install software-properties-common
sudo apt-key adv --recv-keys --keyserver hkp://keyserver.ubuntu.com:80 0xF1656F24C74CD1D8
sudo add-apt-repository 'deb [arch=amd64,i386,ppc64el] http://mariadb.mirrors.ovh.net/MariaDB/repo/10.2/ubuntu xenial main'
sudo apt update
sudo apt install mariadb-server

You database should now be MariaDB 😉

Published on by Nayar

How to check your MyT internet usage #Mauritius

Mauritius’s biggest Internet Service Provider still caps internet for poor people to 1Mbps after having exceeded a quota. Here’s how to know how much internet you got left

1. Go to myt.mu > my.t home > Check My Account

You’ll get a page like this:

2. Call 8900 from your mobile phone and ask them for the password.

3. Once logged in, you shall see how much data allowance you got left:

 

Published on by Nayar

Duplicate Monit IDs in MMonit

when you’re using MMonit software with multiple VMs cloned from a template with monit installed, there are sometimes 2 VM get the same monit IDs. You’ll notice that there are errors on your MMonit dashboard which disappears after a while.

To view the monit id of your VMs, type the following command on your terminal

# monit -i

What do you do if you have hundreds or thousands of VMs? How will you know which ones have duplicate IDs?

I implemented a solution using SQL Triggers.

CREATE TABLE `duplicate_monitids` (
`ipaddrin` varchar(255) NOT NULL DEFAULT ”,
`monitid` varchar(255) DEFAULT NULL,
PRIMARY KEY (`ipaddrin`)
)

delimiter //
CREATE TRIGGER duplicate_monitids AFTER UPDATE
ON host
FOR EACH ROW
BEGIN
INSERT INTO duplicate_monitids(ipaddrin,monitid) VALUES(NEW.ipaddrin,NEW.monitid);
END//
delimiter ;

Then to view the VMs which have duplicate IDs, run the following SQL Query

select ipaddrin from duplicate_monitids where monitid IN (select monitid from duplicate_monitids group by monitid having count(*) > 1);

Published on by Nayar

Playing with Microsoft’s Sharepoint REST API

I couldn’t get Sharepoint to be loaded as an External Storage in Nextcloud. I had find a way to use the old school `curl` to debug the problem.

To properly authenticate, you will have to add some extra parameters to curl

$ curl –ntlm –negotiate -u <Domain>/<Username>:<Password> “http://<url>/<site>/_api/Web/getfolderbyserverrelativeurl(‘%2F<site>/<Folder>’)?$select=Length,TimeLastModified” -v

Notice the `–ntlm –negotiate`. These parameters enable “NTLM Authentication Scheme for HTTP” rather that the usual HTTP Basic Auth. This in turns make lots of back and forth between the curl and MS Sharepoint.

The logs of my HAProxy looks like this. We can see that the curl request has made 3 HTTP requests.

web sharepoint/sharepoint 0/0/1/8/9 401 503 - - ---- 2/2/0/1/0 0/0 "GET /my/_api/Web/getfolderbyserverrelativeurl('%2Fmy/MeraDocs')?=Length,TimeLastModified HTTP/1.1"
web sharepoint/sharepoint 0/0/0/8/8 401 830 - - ---- 2/2/0/1/0 0/0 "GET /my/_api/Web/getfolderbyserverrelativeurl('%2Fmy/MeraDocs')?=Length,TimeLastModified HTTP/1.1"
web sharepoint/sharepoint 0/0/0/15/18 200 3314 - - ---- 2/2/0/1/0 0/0 "GET /my/_api/Web/getfolderbyserverrelativeurl('%2Fmy/MeraDocs')?=Length,TimeLastModified HTTP/1.1"

However I was getting a 404 response in the third response initially. Turns out the API endpoints are different for OneDrive, SharePoint Online and SharePoint Server 2016:

Since I was using SharePoint Server locally, I chose the 2nd endpoint and it worked perfect.

[1] http://www.commandlinefu.com/commands/view/7005/get-a-file-from-sharepoint-with-curl

[2] https://stackoverflow.com/questions/15697157/using-curl-with-ntlm-auth-to-make-a-post-is-failing

[3] https://docs.microsoft.com/en-us/onedrive/developer/rest-api/getting-started/sharepoint-server-2016

Published on by Nayar

Enabling UDP load-balancing with Nginx on Debian 9 (Stretch)

User Datagram Protocol (UDP) is commonly used for DNS resolution and video/voice streaming applications. The advantage of UDP over TCP is that it has less overhead (smaller packet size). You can therefore send more data on your network with less latency. However this comes at the expense of data reliability.

Lemme guide you to how setup an Nginx server (10.0.0.5) which forwards UDP packets from port 514 to a Graylog server (10.0.0.10) on port 514 itself. We will be sending logs from a VM on 10.0.0.2

On your nginx server:

# echo “deb http://nginx.org/packages/debian/ stretch nginx” > /etc/apt/sources.list.d/nginx.list
# apt-get update
# apt-get install nginx

You should now have nginx installed. Paste the following snippet in your `/etc/nginx/nginx.conf`

stream {
  upstream graylog_upstreams {
    server 10.0.0.10:514;
  }

  server {
    listen 514 udp;
    proxy_pass graylog_upstreams;
    proxy_responses 0;
    proxy_bind $remote_addr transparent;
  }
}

Check if Nginx is listening on UDP port 514

root@prod-r7-nginx:~# ss -ntplu

However if you sending data to this port from another machine, you’ll notice that no data is sent to the backend server. Despite `tcpdump` will see the data coming and being sent.

IP 10.0.0.2.38696 > 10.0.0.5.514: SYSLOG kernel.info, length: 120
IP 10.0.0.2.45605 > 10.0.0.10.514: SYSLOG kernel.info, length: 120

We need to tell the kernel to actually route IP addresses which doesn’t belong to him thus acting like a router. We do so by the following command

sed -i "s/#net.ipv4.ip_forward.*/net.ipv4.ip_forward=1/" /etc/sysctl.conf
echo 1 > /proc/sys/net/ipv4/ip_forward

And that’s it 🙂

Do you like nginx’s UDP loadbalancing feature?