Alon Gubkin's questions

What's the most effecient way to prevent DoS attacks for game servers?

Currently I do something like this:

iptables -A INPUT -p udp --dport 27015 -m length --length 28 -j DROP

Is it the best way?

How can I recursively bzip2 all files that do not end with the .bz2 extension in Linux?

I've sym-linked a directory, and now I want to change a specific file in the linked directory, without changing it in the target directory. I don't want to copy the whole directory.

What can I do?

I bought a new VPS running CentOS 5.5, and I'm trying to upgrade my kernel. I've downloaded, compiled and installed it sucessfully, and now I need to set it up in the grub settings. But there's no grub directory in /boot.

Where is, then, the /boot/grub/menu.lst or grub.conf file?

Edit: When I do rpm -ql grub it throws package grub is not installed. How can I know the boot loader and change its settings?

[root@server css]# find /boot -exec rpm -qf {} \;
filesystem-2.4.0-3.el5
file /boot/System.map-2.6.33.5-rt23.old is not owned by any package
file /boot/System.map-2.6.33.5-rt23 is not owned by any package
redhat-logos-4.9.99-11.el5.centos
file /boot/System.map is not owned by any package
file /boot/vmlinuz is not owned by any package
file /boot/grub is not owned by any package
redhat-logos-4.9.99-11.el5.centos
file /boot/initrd-2.6.33.5-rt23.img is not owned by any package
file /boot/vmlinuz-2.6.33.5-rt23 is not owned by any package
file /boot/vmlinuz-2.6.33.5-rt23.old is not owned by any package

[root@server css]# rpm -ql lilo
package lilo is not installed

[root@server css]# head -c 5000 /dev/xvda | strings
head: cannot open `/dev/xvda' for reading: No such file or directory

Hey, Some script kiddies are crashing my clients' game servers (that are based on Linux). In order to serve the best service, I'm looking for a way to find what packets does the crashers send, so I can block it later.

So, I need a simple program, that will log every packet that sent or get to/from the server software, from ALL clients. As I said, the game server software is based on Linux (Ubuntu 9.10), so the program should support Linux. The game server software, is not open source.

Thanks.

If I have a web site on a shared server, and I want to move it to a dedicated server, what should I buy: A strong PC with Linux, or Mac OS X Server?

I've set a virtual directory in /etc/apache2/sites-available/default like so:

    Alias /lynx/ "/home/srv1100/"
    <Directory "/home/srv1100/">
            Options Indexes MultiViews FollowSymLinks
            AllowOverride All
            Order allow,deny
            Allow from all
    </Directory>

every file is accessible when I write http://127.0.0.1/lynx/... I want that only files, which their extension is NOT "bsp" or "nav" and will be accessible. I can't put them in other directory.

Any ideas?

Thanks.

How can I set full permissions to a user in a specified dir in linux?

Is it possible to install Xen as a standalone operating system, without any existing linux distribution? If yes, how?

Thank you.

I've an Ubuntu Server. I installed vsftpd. I want that specific user will have full premissions to /var/www/someDirectory and her child directories/files. So I created a user with this commands:

useradd -b /var/www/someDirectory -d /var/www/someDirectory user1
passwd user1
chown user1 /var/www/someDirectory

It's working, and when this user login to the ftp, he's automatically in the path /var/www/someDirectory. The problem is, he can remove the someDirectory from the path, and see /var/www... he can write any path and he have full premssions to it...

I want that he will only can see/write/any premssion the /var/www/someDirectory and her child directories, and no other directory in the system.

How can I do it?

Thank you so much and sorry for my English - I hope you understood me.

What is a cookie-free domain? I've seen these words many times but I never understood what it is.