Category Archives: GNU/Linux utils

Various GNU/Linux utilities and their usage examples

Redis: fork – Cannot allocate memory, Linux, virtual memory and vm.overcommit_memory

28 August 2019
 

 Currently, I’m configuring a Redis as a caching service for our application and during that, I faced with the question: do I need to set vm.overcommit_memory to the value 1, i.e. disable it – or not? The question is quite old for me, see The story, but only now I found time to get to… Read More »

Debian: unattended-upgrades – automatic upgrades installation with email notifications via AWS SES

23 May 2019
 

 A unattended-upgrades package performs automated upgrades installation on Debian/Ubuntu systems. It’s a Python script (1500 lines) located at /usr/bin/unattended-upgrade (and /usr/bin/unattended-upgrades is a symlink to the /usr/bin/unattended-upgrade). CentsOS/RHEL analog – yum-cron. Install it: The main config file is /etc/apt/apt.conf.d/50unattended-upgrades where upgrade types, email settings etc can be configured. Upgrades related schedules are done in the… Read More »

Linux: GPG-keys, Pass – passwords manager, and passwords import from the KeePass database

25 April 2019
 

 pass – a password manager for Linux/UNIX. Stores data in tree-based directories/files structure and encrypts files with a GPG-key. In Arch Linux present by default, in Debian can be installed using apt from default repositories: For macOS can be installed with Homebrew: The pass itself is just a bash-script: GPG keys management Creating GPG key… Read More »

Kubernetes: running Minikube on Arch Linux

27 March 2019
 

 Minikube – a utility to run a Kubernetes cluster locally on your PC. It can use Virtualbox, VMware, Hyper-V etc hypervisors which will be used to create a virtual machine with a Kubernetes cluster. Minikube is a great tool for developers or DevOps engineers to test deployments/services etc without the need to create and configure… Read More »

What is: chroot – system call and utility in Linux

23 March 2019
 

 chroot() was added to the Version 7 Unix in 1979 and used for filesystem isolation. In fact, it’s the predecessor of the whole current containerization idea, just now there are namespaces and cgroups are used while earlier chroot was used to create an environment which is isolated from a host and can be used for… Read More »

AWS: CLI named profiles

19 March 2019
 

 AWS CLI supports so-called named profiles stored in the configuration file .aws/config and ~/.aws/credentials file with keys which by default contains the… Well – the “default” profile. An additional profile can be added using the aws configure command with the –profile option. Here is an example of such file with already existing two profiles:

Linux: LVM – pvcreate Device /dev/sdb4 excluded by a filter.

9 March 2019
 

 During new Linux set up – suddenly got a weird message. It happen just because of my carelessness and haste. Let’s create new partition: Check new partition size: sdb4 8:20 0 1K 0 part – Er… What? Okay – the simplest solution is just to drop it and re-create: 442.2G – looks good? Check again… Read More »