Category Archives: SysAdmin

Fix hibernate on Thinkpad X60 with 12.04 Precise Pangolin

Just for the record, I’ve spent like the last two hours of my life checking why Kubuntu would not hibernate properly.

After checking that the conditions explained here matched, and increasing my swap memory to at least the size of the system memory (I just upgraded the hardware after setting the swap partition), I finally found the solution in

Thanks, askubuntu!

FTP server on Ubuntu

I write this post more as a reminder for myself than as a generic tutorial. Anyway, it is about a precise FTP server configuration on Ubuntu that might or might not be useful for other people. It is just useful in the environment I am using (web server, just one Unix user, some FTP accounts). Here we go:

The server that I’ve used in several cases, and which I prefer just because it is simple enough to have it running quickly, is VSFTP (Very Simple FTP). It works in integration with the machine’s users so that we only need to add users to the server in order to have them available for the FTP daemon.  Once the server is installed, a few configurations must be done. In file /etc/vsftpd.conf:

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Start a service or execute a script on boot on Ubuntu/Fedora

I have a couple of servers with different Linux distributions (Ubuntu/Fedora) on my hands, which normally work continuously well. However, from time to time they reboot as they are hosted in a shared farm of virtual servers. It was in the first of those reboots when we noticed that neither Apache, neither MySQL servers were automatically launched on start-up, which should be the default configuration in an environment like ours.

So, I’d like to add another new trick to my the knowledge pool, which I expect to be useful for others as well: how to configure scripts and services to run after the system boots?

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Tunneling a multipart POST message through PHP and CURL

In this post I’m going to cover a particular solution to a given problem we’ve faced up in our last project. Let’s set the background: there is a complex web application under development on a shared virtual machine, installed on a subdomain of a public network that will change when going to production. We have also a commercial website hosted in a shared server under a domain that should not change, since it is our first step out of this virtual farm.

For this project, we require to integrate some cameras which send pictures via GPRS connections to the server, and we want to provide some user authentication to avoid having anybody posting whatever to this web service. So, we have developed a controller in Code Igniter which gets a camera ID / password from POST, and also the bytes for the image, and proceeds to do some filtering. For instance, camera ID and password should match with the values previously registered in the database, and the picture should be MIME image/jpeg, with a limit of 2MBs. Up to now, nothing special, tested and working with POSTS from the within the website.

The problem came when we found out that cameras only allow to send their information to a root domain, to a particular file, let’s say upload.php. So, we would only need to put this file in the root path and it’s done. Unfortunately, doing so in the application virtual server would result on flashing again all the cameras once we move to a new server and set up a final domain name. We might be able to install this receiver in the commercial website root path, but then we would require to send the message back to the application server in any way, so it is not the best solution we want to solve this issue.

‘Just add a domain that points to this subdomain and you are done’ would you say. Well, yes, that would have done the trick. Unfortunately, we cannot host this domain in the machine since we have no administrator rights on the servers farm. Nor can we just use this external domain because it produces an HTTP redirection which, to make things worse, is not supported by the camera. We’ve even tried with cloaking the url of the receiver with an external subdomain, with no success – since cloaking wraps the real content inside an iframe and it breaks the POST message.

What a headache! it seemed there was no way to implement the system with the full functionality we wanted…

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