The ss command is used to show socket statistics. It can display stats for PACKET sockets, TCP sockets, UDP sockets, DCCP sockets, RAW sockets, Unix domain sockets, and more. It allows showing information similar to netstat command. It can display more TCP and state information than other tools. It is a new, incredibly useful and faster (as compare to netstat) tool for tracking TCP connections and sockets. SS can provide information about:
- All TCP sockets.
- All UDP sockets.
- All established ssh / ftp / http / https connections.
- All local processes connected to X server.
- Filtering by state (such as connected, synchronized, SYN-RECV, SYN-SENT,TIME-WAIT), addresses and ports.
- All the tcp sockets in state FIN-WAIT-1 and much more.
Lets see how much effort it is going to take to convert this configuration to entirely different firewall platform – PF on OpenBSD. There are different ways to do this. I could make a copy of each member firewall (linux-test-1 and linux-test-2), set platform and host OS in the copy to PF and OpenBSD and then create new cluster object. This would be a sensible way because it preserves old objects which helps to roll back in case something does not work out. However, to make the explanation shorter, I am going to make the changes in place by modifying existing objects.
They say – there’s no such thing as a free lunch. But, Linux and FOSS software can be used to start, run and grow your business for, you guessed it, free. February survey of IT managers by IDC indicated that hard times are accelerating the adoption of Linux. The open source operating system will emerge from the recession in a stronger data center position than before, concluded an IDC white paper.
Today, I’ve upgraded total 8 servers from 4GiB to 8GiB to improve performance of system by inserting additional memory modules. We started each server and checked for memory count at console. All severs booted normally after the upgrade and services such as SMTP, NFS, CIFS, HTTP started as expected. Shortly, afterwords I got a call from help desk about pop3 server for slow performance.
Is Linux is virus free? The author of foobar blog provides some insight about the same. Linux users can’t just catch a virus by email or downloading malware from the Internet, contrary to “those Windows users”. From the foobar blog post:
Then you save an email attachment under Linux, the execute flag is normally NOT set and thus, the file can’t be executed just by clicking on it. So, no luck?
Ubuntu Pocket Guide and Reference has been released and available for download from the official (authors’) website. This guide is written by Keir Thomas and he claims that it is a totally unique and concise guide for everyday Ubuntu user.
Excellent article! It explains how programs are laid out in memory.
From the blog post:
Memory management is the heart of operating systems; it is crucial for both programming and system administration. In the next few posts Iâ€™ll cover memory with an eye towards practical aspects, but without shying away from internals. While the concepts are generic, examples are mostly from Linux and Windows on 32-bit x86. This first post describes how programs are laid out in memory. Each process in a multi-tasking OS runs in its own memory sandbox. This sandbox is the virtual address space, which in 32-bit mode is always a 4GB block of memory addresses.
=> Anatomy of a Program in Memory
Some time ago ext4 was released and available for Linux kernel. ext4 provides some additional benefits and perforce over ext3 file system. You can easily convert ext3 to ext4 file system. The next release of Fedora, 11, will default to the ext4 file system unless serious regressions are seen. In this quick tutorial you will learn about converting ext3 to ext4 file system.
Recently, I noticed that the timeout values differ on CentOS v5.x and RHEL Linux 5.x guests on VMWare ESX4 and ESX3.5.
I’ve already written about setting the MTU (Maximum Transmission Unit) under Linux including Jumbo frames (FreeBSD specific MTU information is here).
With this quick tip you can increase MTU size to get a better networking performance.