TOP 8 || BEST Linux Command Line Tools

Here they are... my eight favorite linux command line tools. 

#8) systat

All systems should have systat installed.  Systat is the easiest way to get basic server performance logging running on a system.  Systat includes the utility sar.  Sar tracks system utilization over time.  There are few things more frustrating then trying to determine what happened over night on your server, and you don’t have any data on the performance of the box because sar is not installed.

#7) rsync

Moving large groups of files around is made a lot easier with rsync.  Rsync computes a unique hash of each file you would like to copy and compares it to your target.  If rsync finds a matched hash, the source and destination files are the same, and file copying is skipped.  Skipping files that have already been copied can really cut down the work effort! Running an rsync in cron is an easy way to keep a backup or replica of data files up to date.

#6) telnet

Telnet is a granddaddy of network tools. Telnet and its server side daemon, telnetd, for many years provided remote console connectivity to servers and network gear.  As it passes traffic in plain text including login information, it has rightly been relegated to the landfill for antiquated technologies.  I haven’t connected to a telnet server in at least a decade. However, the client program is still useful.  Telnet to a well know port enables an interactive session over TCP to many common network programs that pass data in plain text, like HTTP, dns, smtp and even SSH.  SSH doesn’t pass interactive data, but most SSHd servers will tell you the version of SSHd you have connected to.  It’s good for simple tests of network connectivity or for passing protocol commands over the command line.

#5) emacs 

I am a vi user myself, but I admire the heck out of emacs. I recall vividly, back in my WebLogic days in the late 90s, setting up a new developer, Anno Langen. Bob Pasker was walking Anno through the environment. What has stuck in my mind was there 30-minute conversation filled with backslapping and high fives as they compared their emacs macros. For all you emcas people out there, I salute you.

#4) lynx

It may come as a surprise that I have included a text base web browser in a list of must have network tools. But having an actual browser in your console is handy. There are times when it is easier to fire up lynx to smoke test the content of a web page without having to exit the console. Command line tools like wget or curl, don’t always do the job. Sometimes you want an interactive session, not just a single get or post.

#3) mtr

Back in the day, traceroute was a common tool for tracing the path of packets from a source to a destination. It relied on ICMP responses to generate its maps. Because these same useful ICMP responses have been exploited to generate denial of service attacks they have been largely turned off on the Internet. Instead of getting a nice list of hosts between you and your target with useful timing data indicating where in the network there are bottlenecks, you get back a lot of no-replies. MTR to the rescue!  Somewhat similar in look and feel to traceroute, MTR relies on UDP responses to generate its network maps. Once again, we can see where the network bottlenecks are.

#2) nmap

NMAP is a very useful tool for scanning networks and ports. It’s a useful way to uncover information about what system is on the other end. If an nmap reveals port 3369 is open, chances are pretty good you are looking at a windows server. Nmap is also a quick and easy way to scan a range of IP addresses to see what’s on your network and how many IP addresses are in use.

#1) nc

nc may be my favorite of any network tool. What makes nc particularly awesome is its ability to open an ad hoc TCP or UDP port on any available port. This is a great way to test network connectivity between systems and networks during the network build phase, before applications are installed. 

So what do you think? Is there a favorite of yours that is not on the list? Please let me know in the comments.