Debian

Increase file descriptors for Transmission on Linux

Samat Jain — Tue, 05 Apr 2011 23:31:11 +0000

Have you run out of file descriptors for Transmission? The torrent will be stopped (for no apparent reason), and when you examine it, you’ll see an error similar to:

$ transmission-remote -t 1 -i | grep -i 'open files'
Unable to save resume file. Too many open files.

Time to increase the number of file descriptors available. This article is tailored towards Debian and Ubuntu.

It’s unlikely you’ll need to raise your system’s global limit. Check with:

$ cat /proc/sys/fs/file-max
397460

The OS needs a couple thousand file descriptors for itself. Make sure to make space for them with whatever numbers to choose below. In my case, I’ve more than enough.

If you still need to raise your system’s limit, you can easily; to set it to a million (which will be remembered across reboots):

sudo sh -c "echo fs.file-max=$(dc -e '2 20 ^ p') > /etc/sysctl.d/file-descriptors-max.conf
sudo service procps restart

While you may not need to change your system’s global limit, you probably will need to change the limit for your users. Check that limit with:

$ ulimit -Sn
1024
$ ulimit -Hn
1024

If you’re working with hundreds of torrents (each with dozens to hundreds of files) with Transmission, this isn’t enough. To let a user have a few thousand (in the below example, 16,384, with 128 more for the hard limit), create a new file /etc/security/limits.d/debian-transmission.conf:

sudo sh -c "echo debian-transmission soft nofile $(dc -e '2 14 ^ p')" > /etc/security/limits.d/debian-transmission.conf
sudo sh -c "echo debian-transmission hard nofile  $(dc -e '2 14 ^ 2 7 ^ + p')" >> /etc/security/limits.d/debian-transmission.conf

Replace “debian-transmission” with the user that is running Transmission.

For the changes to go into effect, you need to logout completely (e.g. close multiplexed SSH connections, etc), and log back in again. Or to be sure, just reboot to make sure changes kick in. You’ll see you have many more file descriptors available:

$ ulimit -Sn
16384
$ ulimit -Hn
16512

Now, we need to configure Transmission to use this many. In /etc/transmission-daemon/settings.json, find the open-file-limit option and set to a larger number (e.g. 16000 or so). When done, restart transmission-daemon:

sudo service transmission-daemon restart

If you’re not running Transmission as a system user, edit the right settings.json and restart the daemon appropriately.

That’s it. Have fun!

Topic:

Linux

Debian

Ubuntu

High-resolution text console with uvesafb and Debian

Samat Jain — Wed, 10 Nov 2010 00:08:29 +0000

While you may rarely use the console on your server, it’s nice to have a high-resolution display just to see that many more columns and rows. Linux’s vesa module (via the vga= parameter) has been around for a while and made this possible, provided you kept up with what VGA mode number to use and don’t mind the spotty hardware compatibility.

While KMS is the way to do this in the future, it doesn’t help us with the drivers and hardware we have now. A new kernel module, uvesafb, mainlined in 2.6.24, is another, new option. In addition to specifying modes in a more user-friendly way (e.g. 1280x1024-32 for 32-bit color, with a 1280x1024 resolution), hardware compatibility is better—in particular, you can now get a high-resolution text console with NVIDIA display adapters.

In the following, I describe how to use uvesafb on Debian and derivative distributions (e.g. Ubuntu). The instructions assume kernel 2.6.27 or higher (Debian 6.0 (squeeze) and Ubuntu 8.10 (Intrepid Ibex), or later).

Topic:

Speeding up SpamAssassin rule processing on Debian and Ubuntu

Samat Jain — Thu, 02 Oct 2008 19:01:57 +0000

SpamAssassin is one of the most-used spam filtering systems in use today. Unfortunately, because there are so many different ways SpamAssassin can be used, SpamAssassin remains subject to many performance problems. Fortunately, there are several speed-ups and optimizations that can be applied to most SpamAssassin installations to speed up its rule processing, especially on Debian and Ubuntu GNU/Linux-based systems. These instructions can be adopted to other operating systems as well.

This article does not discuss configuring your mail filtering system (i.e. procmail, maildrop). This depends completely on your setup, and more than likely there are plenty of other articles that describe the best way to setup what you want.

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Topic:

Installing Java 2 on Debian, The Debian Way

Samat Jain — Thu, 22 Sep 2005 01:04:00 +0000

I can never remember how to install Java on Debian, so here’s my version on how to do it the Debian Way (TM).

Download the Sun Java 2 Runtime environment or Development Kit from Sun’s Java site. The file you download should have a “.bin” extension. Then install:

apt-get install java-package fakeroot

java-package is a set of Debian scripts for creating your own Debian-ized Java package. fakeroot lets you run certain programs as root, such as the Debian package creation process. After these are installed, run:

fakeroot make-jpkg jdk-.bin sudo dpkg -i sun-j2sdk.deb

The first creates a Debian package from the Sun binary installer, while the second installs the created Debian package.

This will fulfill all Java dependencies in Debian, something you would not get if you installed Java via some other method. It’s also the “official” Java, as opposed to using something like Blackdown, and makes you less reliant on having to rely on other people for packaging. For example, I used this to create my own AMD64 64-bit Java package.

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Debian's mailing lists: a spammer's delight

Samat Jain — Mon, 01 Aug 2005 15:38:00 +0000

Since e-mail aliases are basically free (it’s a line in a text file), I’ve started the habit of creating new e-mail aliases for what I think have a “high-risk” of getting harvested by spammers.

I created one for Debian’s mailing lists a week ago, and today I received my first spam e-mail to that address. It was an eBay phishing scheme.

Debian’s public mailing list archives make no attempt at address obfuscation–any web crawler is free to come and take as many valid e-mail addresses as they want. My attempts at complaining about this appear to have fallen on dead ears–no one appears to care.

At least it’s nice to definitely know where your spam is coming from.

Topic:

Debian

Debian-based x86-64 Live CDs

Samat Jain — Fri, 15 Jul 2005 02:53:00 +0000

At the moment, there are only two semi up-to-date x86-64 (that is, for Athlon-64, Intel EMT64, and Opteron) Debian-based live CDs.

Knoppix-64, based on Knoppix 3.4 (somewhat out of date as Knoppix 4.0 is out)
Ubuntu, which is kept up to date and is available tucked away on their FTP site

I’m getting Ubuntu now to try out on my new workstation.

Topic:

Linux

Debian