Linux and recursion are on very good speaking terms. In fact, a number of Linux command recurse without ever being asked while others have to be coaxed with just the right option. When is recursion most helpful and how can you use it to make your tasks easier? Let’s run through some useful examples and see.Easy recursion with lsFirst, the ls command seems like a good place to start. This command will only list the files and directories in the current or specified directory unless asked to work a little harder. It will include the contents of directories only if you add a -R option. It provides a -r option, but that option causes the listing to be in reverse order as shown below while -R delves into the various subdirectories.$ ls /usr/localbin etc games include lib man sbin share src$ ls -r /usr/localsrc share sbin man lib include games etc bin$ ls -R /usr/local/usr/local:bin etc games include lib man sbin share … [Read more...] about Linux: To recurse or not
If you check the processes running on your Linux systems, you might be curious about one called "kerneloops". And that’s “kernel oops”, not “kerne loops” just in case you didn’t parse that correctly. Put very bluntly, an “oops” is a deviation from correct behavior on the part of the Linux kernel. Did you do something wrong? Probably not. But something did. And the process that did something wrong has probably at least just been summarily knocked off the CPU. At worst, the kernel may have panicked and abruptly shut the system down.For the record, “oops” is NOT an acronym. It doesn’t stand for something like “object-oriented programming and systems” or “out of procedural specs”; it actually means “oops” like you just dropped your glass of wine or stepped on your cat. Oops! The plural of "oops" os "oopses".An oops means that something running on the system has violated the kernel’s … [Read more...] about What is a Linux “oops”?
I have Debian Linux VM running on KVM. I think I forgotten the password for the root account and I am no longer able to run ‘su -‘ command. How do I reset the password for the root account for KVM VM which is in qcow2 format? You can modify images with guestfish. It is a shell and command-line tool for examining and editing virtual machine filesystems. It uses libguestfs and exposes all of the functionality of the guestfs API. This page shows how to use guestfish to change the root account password. How to install guestfish If you are using CentOS/RHEL use yum command:$ sudo yum install libguestfs-tools$ sudo dnf install libguestfs-toolsapt command/apt-get command:$ sudo apt install libguestfs-tools Step 1 – Shutdown guest VM Run the following virsh command:# virsh list Id Name State ---------------------------------------------------- 2 debian9-vm1 running To shutdown the VM named debian9-vm1:# virsh shutdown 2# … [Read more...] about How to reset forgotten root password for Linux KVM qcow2 image/vm
Today is launch day for Sylabs — a new company focused on promoting Singularity within the enterprise and high-performance computing (HPC) environments and on advancing the fields of artificial intelligence (AI), machine/deep learning, and advanced analytics.And while it's launch day for Sylabs, it's not launch day for the technology it will be promoting. Singularity has already made great strides for HPC and has given Linux itself more prominence in HPC as it has moved more deeply into the areas of scientific and enterprise computing. With its roots at Lawrence Berkeley National Laboratory (Berkeley Lab), Singularity is already providing a platform for a lot of heavy-duty scientific research and is expected to move into many other areas, such as machine learning, and may even change the way some difficult analytical problems are approached.If you’re not familiar with Singularity as a relatively new (late 2015 introduction) container technology, you might be intrigued by … [Read more...] about It’s launch day for Sylabs: Promoting portable high-performance containers for Linux
For those of us who cut our technical teeth on the Unix/Linux command line, the relatively new ranger makes examining files a very different experience. A file manager that works inside a terminal window, ranger provides useful information and makes it very easy to move into directories, view file content or jump into an editor to make changes.Unlike most file managers which work on the desktop, but leave you to the whims of ls, cat and more to get a solid handle on files and contents, ranger provides a very nice mix of file listing and contents displays with an easy way to start editing. In fact, among some Linux users, ranger has become very popular.As you start ranger, you will see a display that looks something like this:[email protected] /home/shs/binshs bin 5 case1 Desktop 0 killit Documents 11 prime Music 0 sieve Pictures 0 tryme Public 0 Reports … [Read more...] about The Linux ranger
Want to check which Linux kernel version your distro is running on? Well, it’s pretty easy to find out. All you need is a working keyboard, a few fingers, and a pair of eyes. Oh, and a terminal emulator. But before we show you the command that lets you quickly find which kernel version you’re running on, let’s consider a few reasons why you might want to check in the first place. What Kernel Version Are You Running? Tux is the Linux mascot One thing unites every Linux distro out there, from Ubuntu to Fedora, from Solus to Arch: the Linux kernel. But what is the Linux kernel? There are plenty of in-depth, super complex definitions which describe what the Linux kernel is in detail. But the ‘for dummies’ way to describe it is as the engine of your operating system, atop which everything else sits. The Linux kernel is what allows everything you see on your computer to be there; it’s responsible for managing hardware resources, allocating memory, … [Read more...] about How to Check Which Linux Kernel Version You’re Using
Just about every Linux user is familiar with the process of piping data from one process to another using | signs. It provides an easy way to send output from one command to another and end up with only the data you want to see without having to write scripts to do all of the selecting and reformatting. There is another type of pipe, however -- one that warrants the name "pipe", but has a very different personality. It's one that you may have never tried or even thought about -- the named pipe.One of the key differences between regular pipes and named pipes is that named pipes have a presense in the file system. That is, they show up as files. But, unlike most files, they never appear to have contents. Even if you write a lot of data to a named pipe, the file appears to be empty.Before we look at one of these empty named pipes, let's step back and see how a named pipe is set up. You would use a command called mkfifo. Why the reference to "FIFO"? Because a named pipe is also known as a … [Read more...] about Why use named pipes on Linux?
I am a new Vim text editor user. I am writing Python code. Is there is a way to see Python documentation within vim and without visiting the Internet? Say my cursor is under the print Python keyword, and I press F1. I want to look at the help for the print keyword. How do I show python help() inside vim? How do I call pydoc3/pydoc to seek help without leaving vim? The pydoc or pydoc3 command show text documentation on the name of a Python keyword, topic, function, module, or package, or a dotted reference to a class or function within a module or module in a package. You can call pydoc from vim itself. Let us see how to access Python documentation using pydoc within vim text editor. Access python help using pydoc The syntax is:pydoc keyword$ vim ~/.vimrc nnoremap <buffer> H :<C-u>execute "!pydoc3 " . expand("<cword>")<CR> nnoremap <buffer> H :<C-u>execute "!pydoc3 " . expand("<cword>")<CR> Save and close the file. Open vim text … [Read more...] about How to access/view Python help when using vim
One of the most exciting things to happen in the Linux world in the last few years is the emergence of containers -- self-contained Linux environments that live inside another OS and provide a way to package and isolate applications. They're not quite virtual systems since they rely on the host OS to operate nor are they simply applications. Dan Walsh from Red Hat has said that on Linux "everything is a container", reminding me of the days when people were claiming that everything on Unix was a file, but the vision has less to do with the guts of the OS and more to do with explaining how containers work and how they are different than virtual systems in some very interesting and important ways.To get some perspective on containers, I spoke with Joe Brockmeier, a Senior Evangelist at Red Hat. He suggest that we can think of containers as lightweight virtual machines, though he pointed out that we'd not be technically correct. Container runtimes talk to the host's kernel and run … [Read more...] about Exploring Linux containers
Linux inventor Linus Torvalds has never been one for diplomacy. He previously said “fuck you” to Nvidia for not supporting Linux, and now Intel has angered him enough to generate some more expletives. In a message to the Linux kernel mailing list on the weekend, Torvalds has expressed his dismay at Intel’s security updates to protect against the major Spectre variant 2 CPU vulnerability. The industry has been scrambling to fix the Meltdown and Spectre vulnerabilities, and the variant 2 of Spectre has been particularly challenging. “What the f*ck is going on?” asks Torvalds, claiming that Intel is doing “insane things” that “do not make sense” to protect against the Spectre variant 2 vulnerability. “As it is, the patches are COMPLETE AND UTTER GARBAGE,” claims Torvalds. At the heart of the issue is Intel’s approach to Spectre and the associated fixes. The Register points out that Intel’s future processors, at … [Read more...] about Intel’s Spectre fixes are ‘complete and utter garbage,’ says Linux inventor