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Articles in Networking
Show NIC Bandwidth Utilization
Just a quick script that will measure bandwidth utilization in KB/s for all NICs on your server over the specified period of time. You can call the script with an optional time wait parameter in seconds.
Tracking Network Connections Over Time
Firewall changes, datacenter migrations, application re-hostings, server decommissions are just some of the activities where having a record of network connections over time can help avoid confusion and unplanned downtime. To capture all network connections, …
Linux CLI Network Speed Test
The speedtest.net is probably one of the more popular bandwidth testing utilities, Unfortunately, this and many other similar tools require a Web browser with late-version Flash or Java support, which can be problematic on Unix …
Find Available IP Addresses
After a while, available IP addresses on the subnet may become hard to come by. Whatever spreadsheet you used to track IP allocations is likely out of date. Here’s a simple script that will scan …
Practical TShark Capture Filters
The tshark is the command-line interface for Wireshark – a popular open-source network packet analyzer. A seemingly infinite variety of options make tshark an unlikely choice for casual use. Nevertheless, the power of CLI justifies the extra …
Detecting Synology NAS with nmap
Just a quick note for myself on how to find Synology NAS servers on the network without having to use the bulky Windows utility that ships with these systems.
Fail2ban Whitelist IPs
Fail2ban is an excellent security tool that will do a good job safeguarding your server. However, using fail2ban you may run into two issues: friendly fire and inability to permanently ban hostile networks. I already …
Identifying Available IPs on the Network
At some point available IPs on your network may become few and hard to come by. Documentation becomes outdated and does not accurately reflect which IPs are still in use. A good starting point would …
Permanently Ban IP with Fail2Ban
If you’re not familiar with Fail2Ban: it’s a log analysis tool that detects failed login attempts for your SSH, FTP, etc services and uses IPTools firewall to temporarily drop connection requests from the offending IP addresses. …
Configure Anonymous FTP on Solaris 10
Below are basic steps for configuring anonymous FTP service on Solaris 10. Use with caution.
Enable Basic FTP Server on Solaris 10
Here are a few simple steps to enable a basic FTP server on Solaris 10.
Simple Network Discovery
The bash script below will scan the specified IP range and use dig and nmap to try to determine the fully-qualified domain name, type and the operating environment of any device that responds to network …
Basic Samba Configuration on Solaris 10
Here’s a sample process for installing and configuring a basic Samba server on Solaris 10.
Solaris 10 NFS Server Configuration
As far as NFS servers go, I think the best platform in terms of performance and stability is Solaris running on SPARC architecture. Perhaps this has something to do with the fact that NFS was created for Solaris. Over the years I’ve been working with NFS servers on AIX, HP-UX, Linux, BSD, etc. It always worked better on Solaris.
RPC: Authentication When Mounting Solaris NFS Share
When mounting an NFS share from a Solaris 10 server, you may encounter the “RPC: Authentication” error. You may notice that you are able to mount the share via NFSv4, not not NFSv3. On the NFS server the /var/adm/messages may show the following errors for the client…
Fixing the mount.nfs: rpc.statd is not running Error
The rpc.statd service is used by NFS client to help it recover from loss of connectivity to the NFS server. When rpc.statd is not running, NFS is not able to handle remote file locking. You …
Red Hat: Changing Hostname and IP
Changing hostname and IP is frequently required when a server is being moved from testing or development to production. The process is a fairly simple one, but steps must be performed in a certain order to avoid complications.
Troubleshooting InfiniBand Connections
The following is a brief troubleshooting guide for an InfiniBand network found in common HPC Linux clusters. Running these commands requires OFED 1.5.2 or later package installed on your systems. Additionally, the “pdsh” (parallel shell) command is part of the HP CMU cluster management software (version 4.2.1 used in our example) installed on the head node.
Opening Custom Ports in SuSE Firewall
Most of the servers I work with are already behind an enterprise firewall, so I rarely get to configure a software firewall. In the following example, I installed Webmin and Usermin on a SLES 11 server that had SuSE firewall enabled. Webmin and Usermin by default use ports 10000 and 20000, respectively. These ports are not in the list of common services you would find in the SuSE firewall configuration GUI. There are a couple of ways of adding custom ports to the list of the allowed services.
LPI Invents Linux Commands
It would appear that in order to obtain Linux Professional Institute’s LPIC-2 certification, one needs to know real Linux commands as well as imaginary ones. On the Sample Questions page for LPIC-2 Exam 2 the LPI Linux gurus pose the following question
Windows 7 Black Screen After Booting
I had to power-cycle my Windows 7 64-bit laptop. The bootup sequence looked normal and reached a point where I could see the black screen with the mouse cursor. After this stage my desktop would usually appears, but not this time. I could move the mouse and I could even establish a remote desktop connection to my laptop. But I could not log in. Every time it would reach the same point – the black screen with the mouse cursor – and it would stop.
NFS “Not Owner” Error
The “not owner” error is displayed on the client system (usually Solaris) when attempting to mount an NFS share from a server. This error may appear even though the share is correctly exported and the client system has full access. If you are getting a “permission denied” error, then this article is not for you and you should check here instead.
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