By Adrien | February 23, 2012 | 6 Comments
I propose to you five great commands for:
The kernel is the core of your Linux system. It is frequently updated, and knowing its version may be important for compatibility reasons. Certain programs may require a certain version in order to work properly. It may also be important for some peripherals and modules. As an example, my Ubuntu is based on the official kernel 3.0.0. So far, the latest version is 3.2.5.
To know exactly what kernel you are using, its version, and your computer architecture, use the command:
uname -mrs
With this example, we can clearly see that I am using the official kernel, version 3.0.0. The i686 stands for my computer architecture. Here it means that I am using a 32-bit computer. On the other hand, x86_64 would have indicated a 64-bit architecture.
2. Finding hidden processesTo know what processes are currently running on your machine, most people would recommend the command “top“. Joshua wrote a very good article about it last year at Linux Running Too Slow? Here’s How to Find the Cause. Personally, I find this command very useful, and as Joshua explains, it can even be used to monitor the RAM usage.
However, I am sometimes too lazy to search in the list provided by “top“, and if I already know the name of the program running, I recommend the combination:
ps aux | grep [name of the program]This will have the effect of listing all the current processes, even the smallest ones that will not be picked up immediately by “top“, and then filtering them according to your keywords.
This method will instantly give you the name of the user responsible for this process, the PID number, the CPU usage percentage, the memory usage, the name of the process, etc.
As a side note, if you don’t know how to kill a running process:
kill [PID number]OR
killall [name of the process]3. Listing running modulesModules appeared in version 2.0 of the Linux kernel. They are very useful, and you can consider them as drivers that you can load and remove from the memory. As an example, if you are using a laptop, you probably have a WiFi card. The corresponding modules for that card are probably loaded automatically at start up. If you want to save some battery, you may want to stop the card when you are not using the Internet. Removing the corresponding driver from the memory will then give you a little bit more memory (and you will also be sure that your card is disabled).
But first you need to know which modules are currently running. The command for that is
lsmodThis command is simply the combination of “ls” for listing files in a directory and “mod ” for module (I know, what a surprise).
As a complement to your knowledge, you can add modules with the command
modprobe [name of the module]and remove them via
rmmod [name of the module]These two commands have to be launched by a super-user.
4. Checking disk usageKeeping an eye on your system’s volumes can save you a lot of trouble. You may want to be sure that there is always enough room in /root, and remember to periodically clean your /tmp. For that purpose, there are two great commands:
lsblkand
df -hlsblk displays a tree representation of the partitions of your computer. It also gives you some useful information about the size of these partitions, their type, and their mountpoint.
However, even if lsblk is more visual, I still prefer to use df -h. The latter gives you more information about the remaining space, the size of the partitions, and the percentage of memory in use.
You may have noticed that the command df alone will give you the size in bytes, which might be very hard to interpret. The option -h stands for human readable and gives you the amount of data in gigabytes, megabytes, or whatever is the easiest for a human to understand.
5. Locating binaries and configuration filesOne of the first things that confused me when I left Windows a few years ago was that the file system was completely different on Linux. There is no such thing as Program Files, or a single directory for all the configuration files. But it may be very useful to know where these binaries are. For that purpose, the command:
whereisis among the best. Similarly to
whoamiwhich gives you the name of the current user, or
whatiswhich explains a command quickly, whereis can locate binaries, manual entries, and various configuration files. Its syntax is also very simple:
whereis [name]
In the example above, I asked where Firefox was, and the command returned the location for its binary and various directories, as well as the manual page.
But one of the greatest strengths of whereis is its ability to locate standalone configuration files. Here is another example, where I was searching for rc configuration files:
Such options can become very useful, especially if you are not using Ubuntu but another distribution like Archlinux which requires a serious amount of time to edit these files.
ConclusionWith these commands in your pocket, you will be able to see a little more of what is going on in your system. If you still prefer to have a GUI for that, I would still recommend things like Baobab for the files and Gnome System Monitor in general.
Are you using other commands? Other GUIs? Let us know in the comments.
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Adrien is a young but passionate Linux aficionado. Command line, encryption, obscure distributions... you name it, he tried it. Always improving his system, he encountered multiple tricks and hacks and is ready to share them. Best things in the world? Math, computers and peanut butter!4 Must Have Browser Addons To Protect Your Online PrivacyRandom PostSchedule Your Emails to Send Later With RightInbox Alaric
Nice post…I didn’t know about some of these.
http://www.tahutek.net/ Damar RiyadiGreat post! Thanks for the info :)
AnonymousAdrien, when I attempt to run «lsblk» on my 64-bit Ubuntu Natty box, I get the following :
mhenriday@mhenriday-GA-990FXA-UD3:~$ lsblk
Kommandot “lsblk” hittades inte. [The command "lsblk" was not found.] Menade du [Did you mean]:
Kommandot “lslk” från paketet “lslk” (universe) [The command "lslk" from the "lslk" package (universe)]
which, of course, is another thing entirely. Any idea why I’m getting this response ?…
Henri
AdrienHello Henri,
I tried the same thing on an Ubuntu 11.04 in 64-bit and I got the same error message.
However, there was no problem on a version 11.10. lsblk is part of the util-linux package and as you can see, this package is present on 11.04:
http://manpages.ubuntu.com/manpages/precise/en/man8/lsblk.8.html
http://packages.ubuntu.com/natty/util-linux
I searched a little and so far I can guess that it is related to the Natty. lsblk seems only to work on 11.10 and higher.
Strange but you still have df -h that I recommend.
Adrien
hi, Adrien. Good post,. We re using Openwrt as the basis for a new product and would welcome any comment as to what commands ar eparticularly useful in that type of distribution?
AdrienHello Mr. M2M.
To be perfectly frank, I know very little about Openwrt. But as far as I understand, it can really depend on the type of product that you want. Without any specifications, I can assume that your product will be closely linked to routers and other devices related to the internet. In that case, useful commands can be for firewall, like Iptable, or network scan, like iwlist scan. You can also think of ssh and scp for file tranfers. Finally, I know that a main command for Openwrt is uci, for Unified Configuration Interface. It is responsible for making changes to the filesystem located under/etc/config/.
I hope this helped you at least a little.
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