We recently did some speed testing on a few of the servers on our network, and we were not receiving the speeds expected considering they were sitting on a physical 100mbps ethernet port. The servers were indeed on physical 100mbps connection, however wget (TCP/IP, HTTP Port 80) download tests showed only a max of about 1.5MB/sec (note the 8bit/byte conversion, so this translates to about 12mbits).
Categories: Linux,Software,System Administration,Ubuntu
Did you ever have a situation where you needed to access a website that had an IP restriction in place? I recently had a situation where I needed to access the web via my university connection (due to IP restrictions placed on accessing databases of research papers). They do not have a VPN setup so it is hard to do this off-campus. I do however have access to a linux machine on campus. I am familiar with port forwarding using SSH but I had never used it to actually tunnel web traffic using a web browser on Windows. Turns out it is surprisingly easy! The ssh command to use is: 1ssh -C2qTnN -D 8080 username@remote_host This command sshes to the remote_host, and creates a tunnel on your localhost, port 8080. Note that you need to have private key authentication already set up for this host – it will not work….
Categories: CentOS,Linux,Security,Software,System Administration,Ubuntu
You’ve flashed your old WRT54G or other vanilla router with the Tomato firmware. This itself turns your router into a lean, mean routing machine with QOS, SSH and more, but let’s say we want to take it a bit further. What it we want to get some more stats out of it? In order to do this, we first need to set up a way to pull this information from the router. The best way to do this is to install an SNMP (Simple Network Management Protocol) daemon on the system. The main roadblock we face here is that the system mainly runs in volatile system memory, meaning that every time the system is rebooted the filesystem is reset. Fortunately Tomato provides a way to get around this using CIFS shares. Follow the steps below (as modified from here) to install an SNMP server on a Tomato router. Create a….
Categories: Code Samples,Configurations,Hardware,Linux,Other Code,Other Technology,Programs,Shell,Software,System Administration
Have you ever come across a server that is doing a lot of traffic? Maybe you have logged in to see a process running at 100% CPU, so you know the culprit, but instead of kill -9ing it, wouldn’t it be great to see what exactly it is up to? Or even if you see a process and don’t know exactly what it is doing, and you are just curious what it is up to? As with most issues there are several ways to skin this cat. You can use tcpdump or wireshark to sniff the all of the network traffic on the device. If you know the port the program is running on (you can use lsof for that), you can restrict traffic to that port. But what if the program is jumping ports, or even uses a side-port for some sort of data transmission (UDP?). The main problem….
Categories: CentOS,Code Samples,Linux,Shell,System Administration
Tagged: command line, Linux, network, Security, system admin, traffic
It is easy to do an in-place upgrade of Ubuntu Server from 8.10 ‘Intrepid Ibex‘ to 9.04 ‘Jaunty Jackalope‘. You can do this remotely over ssh or whatever you use to control your server. Best practices say to make sure to backup your server before doing the upgrade. I’ve done several servers this way with no issues! Issue the command: 1sudo apt-get update; sudo apt-get upgrade; sudo apt-get install update-manager-core; sudo do-release-upgrade Follow any prompts to first upgrade the current distribution with the newest packages, then do the release upgrade.
Categories: Linux,Shell,System Administration,Ubuntu
Tagged: System Administration, Ubuntu
Zabbix is an excellent system monitoring package. It does everything from basic availability checking to detailed system resource analysis. It is capable of graphing the variables pulled from the system, and alerting admins if there is a problem or something needed for attention. Once you have the Zabbix server set up, you need to install the client on any systems you want to monitor. Windows systems have a precompiled binary to install. On linux, unix or freebsd systems you’ll need to compile binaries. If you have a range of systems that are homogeneous, you can port the binary to those or also compile it with static dependencies. Below are steps to compile, configure and install the zabbix client: Steps to install a Zabbix Client Download zabbix source code from www.zabbix.com; decompress with ‘tar zxvf’ and cd to directory Configure the make program: ./configure –enable-agent Compile and install the program: make….
Categories: CentOS,Code Samples,Configurations,Linux,Programs,System Administration
Tagged: agent, alerts, monitoring, zabbix
As previously written on this blog, I have set up a display in our lobby at work to display the day’s current events and meetings using Ubuntu and a tiny PC. Since this is a display which is on all day, the screensaver and monitor blanking (and other Energy Star features) are all turned off. Under the auspice of wanting to save energy and also extending the life of a new monitor, someone suggested that we turn off the monitor at night using an electrical timer. A lightbulb went off in my head, that there must be a better way to do this via command line and then run it in the cron. It turns out the solution is very simple. The xset command is the X server preferences command. It has a simple command to turn off the monitor: 1$ xset dpms force off and to turn the monitor….
Categories: Code Samples,Hardware,Linux,Shell,Software,System Administration,Ubuntu
Tagged: display, energy, energystar, lobby, monitor, power, saving
