Raspberry Pi 4
Wow, Raspberry Pi 4 is now available with 8GB of DDR4 memory! This is still a crazy good value for something that costs less than $100 ($75 for just the Raspberry Pi itself, actually) and runs modern operating systems with most of functionality you come to expect from a Linux desktop!
I needed to forward X11 output from one of my Linux servers recently to run virt-manager (manager for virtual machines in KVM), and because it’s been a while I had to download and install X11 server again.
I love reading man pages for even the most basic Unix commands like ls, because there’s always something interesting to learn. Today I discovered that it’s possible to sort ls output by file size.
As I mentioned, I’m building a new Linux based desktop PC – currently running RHEL 8. Since I’m planning it as a primary desktop system for my home lab, I want to eventually migrate workflows from MacBook Pro to the new PC – and this means I want to use my existging LG 5K UltraFine 27” display. This seemed like an interesting Unix Tutorial Project from the very start!
Apparently, Debian installer doesn’t install or activate sudo by default. This means that sudo command is not found the only privilege escalation method available is becoming root via su command. Since I like and use sudo daily, I decided to install and setup it on Debian VM.
I’m slowly improving my Python skills, mostly by Googling and combining multiple answers to code a solution to my systems administration tasks. Today I decided to write a simpe converter that takes Epoch Time as a parameter and returns you the time and date it corresponds to.
I had a server run out of space recently, to the point that it couldn’t complete the yum update. This server ended up corrupting a yum packages database.
Now and then you may notice that apt-get upgrade command keeps a few packages back, meaning they don’t get upgraded. This quick post shows what you can do about it and how to get all the packages upgraded.
Unlike chmod command, chown only becomes useful if run with elevated (root) privileges. In Linux, it is most commonly used with the help of sudo command.
I know that the upcoming Linux Mint release will be based on the just-released Ubuntu 19.04, but just couldn’t wait this long to try Ubuntu 19.04 and all the improvements it brings. So my past few week’s project has been to install Ubuntu 19.04 on my Dell XPS 13 9380 laptop.
This week’s Unix Tutorial Project is super geeky and fun: I’m setting up text-based email archive system using Mutt (NeoMutt, actually), OfflineIMAP and hopefully NotMuch. Will publish a project summary on the weekend.
Call me old fashioned, but I still prefer using ifconfig command. It’s not as cool as the ip command found in recent Linux distros, but familiar and universal enough to be found pretty much everywhere else. This post shows how to install packages to make ifconfig working again.
I really like the Hack font – it’s used in my terminal apps on MacOS, Linux and even Windows workstations. This short post demonstrates how to install Hack font, but you can use the steps to configure any other TrueType Font (TTF) on your system.
One of the most useful and powerful basic Unix commands, chown command allows you to change ownership of specified files and directories – change user or group owner.
As you can imagine, SSH keypairs – combinations of private and public keys – are vital elements of your digital identity as a sysadmin or a developer. And since they can be used for accessing source code repositories and for deploying changes to production environments, you usually have more than one SSH key. That’s why it’s important to know how to inspect SSH key fingerprints.
Since awk field separator seems to be a rather popular search term on this blog, I’d like to expand on the topic of using awk delimiters (field separators).
I have a tiny server in home office, it used to be a Window 8 based entertainment box but I reinstalled it with Ubuntu 18.10 recently enough to run home automation. There has’t been any particular function assigned to this server but I have finally decided what role it will play: it will be an always-on Ubiquiti UniFi controller for my home office network!
diff is a mightly command line tool found in most of Unix and Unix-like operating systems. diff helps you to find differences between files and directories.
Now and then, especially when working on a development environment, you need to stop multiple Docker containers. Quite often, you need to stop all of the currently running containers. I’m going to show you one of the possible ways.
If for whatever reason you stop using a certain service in your Ubuntu install and would like to disable automatic restarting for it upon system reboot, all it takes to do it is just one command line.
Screen Shot 2019-01-05 at 17.29.36.png
dd command, that is pretty much guaranteed to be pre-installed on your Linux or Unix server, can be used to quickly get an understanding of the I/O capability of available storage.
You probably know about curl command: it’s great for downloading web pages or files from a Unix command line. But there’s another great usage curl command has: testing TCP ports connectivity.
One of the very first questions a Linux user asks is about confirming the release (OS version) in use. Knowing release helps with highlighting software dependencies and compatibilities, confirms availability of certain features in your OS and simplifies the process of system administration – certain releases have a preferred set of commands for day-to-day management.
New Linux users often get puzzled by the “mkdir: cannot create directory” errors when taking first steps and trying to learn basics of working with files and directories. In this short post I’ll show the two most common types of this mkdir error and also explain how to fix things so that you no longer get these errors.
IMPORTANT: This is a post from another blog of mine, which I’m shutting down. I like the way these virtualization concepts were worded in such a relatively simple way, so I’m keeping the post 🙂
Many of us have heard about hardware virtualization, but as far as I can see there is still a lot of confusion around this term and surrounding technologies, so today I’ve decided to give a really quick intro. Some time in the future, I’ll probably cover this topic in detail.
I explained how to read the /proc/mdstat in my recent post How To Identify RAID Arrays in Linux, so today is a super quick follow up using one of my systems.
Because I own a number of Raspberry Pi systems, I get roughly the same question quite regularly about each one of them: how can I confirm what this Raspberry Pi model is from the command line? The reason I usually want to know is because the model of the Raspberry Pi hints the Raspbian release that will support it (older Raspbian releases do not have support for the most recent models of Raspberry Pi).
When you want to save yourself from typing an unwieldy command over and over again you can create and use an alias for it. It will then act as a shortcut to the larger command, which you can type and run instead.
The tmux tool, or the terminal multiplexer, is great for allowing you to run multiple terminals side by side. What’s even better is that you can somewhat customize its behavior using the tmux.conf file. The meta key is the prefix you press before you issue a command that controls tmux so you can, for instance, split the terminal in two. By default it is set to CTRL-B, and this is how you can change that.
Some properties of ext2, ext3, and ext4 file systems on Linux and UNIX can be tuned on the fly using the tune2fs command. This includes the file system’s label.
The unrar program, which serves to open and extract popular .rar archives, is often available for install from repositories of a given Linux distribution. That should make installing it easy by using your distribution’s package management system. That can be either a graphical user interface program like Ubuntu Software Center, or a command like tool like apt-get.
Finding out sizes of files and directories in Linux is done using the du command, which estimates their disk space usage. The du command can be used with options that allow you to customize the results you get.
The visudo command is a safe and secure way of editing the /etc/sudoers file on UNIX and Linux systems. /etc/sudoers is instumental for gaining privileged access via sudo command.
The visudo command is a safe and secure way of editing the /etc/sudoers file on UNIX and Linux systems. /etc/sudoers is instumental for gaining privileged access via sudo command.
The mkfs command available in UNIX and Linux operating systems is used to create file systems on various storage devices or partitions. It stands for “make filesystem”, and creating a file system is essentially an equivalent to what is popularly known as “formatting” a disk or a partition with a particular file system type (such as FAT32 or NTFS in Windows).
I had to download a piece of software today for one of the servers which I haven’t used in a while. A question of confirming the 64bit CPU capability came up, and I realized that I never mentioned it here on Unix Tutorial.
I’ve just been asked a question about changing the ownership of files from one Unix user to another, and thought it probably makes sense to have a quick post on it.
Yesterday in my post on numeric userids instead of usernames, I touched briefly the problem of recovering the username if you only know the userid it once had. Today I would like to show you another option which may be available to you when it comes to recovering the usernames of removed users by their userid.
As you know, every file in your Unix OS belongs to some user and some group. It is very easy to confirm the ownership of any file because user id and group id which own the file are always linked to the file. However, sometimes you can’t tell which user owns the file, and today I’m going to explain why. It’s a rather lengthy post and a complicated matter, so please leave questions or comments to help me polish this article off.
Today I’d like to show you the basic usage of rsync – a wonderful, old and reliable tool for incremental data transfers and synchronization of local directories or even data between different Unix systems.
If you’re interested in what exactly your Ubuntu system has got installed, there’s a command you can use to list the packages along with their versions and short descriptions.
If you’re logged in at some remote Linux system and need to quickly confirm the amount of available memory, there’s a few commands you will find quite useful.
Certain situations require you to quickly confirm which files between two directories are different, and while your particular requirements may suggest writing a script for this task, I want to make sure you’re familiar with the basics first – majority of directory comparisons can be done using diff command (yes, that’s right – the same one used for comparing files).
Showing your processes in a hierarchical list is very useful for confirming the relationship between every process running on your system. Today I’d like to show you how you can get tree-like processes lists using various commands.
As you know, Unix filesystems store a number of timestamps for each file. This means that you can use these timestamps to find out when any file or directory was last accessed (read from or written to), changed (file access permissions were changed) or modified (written to).
Another quick answer to the question I see a lot in search queries on this blog: listing directories in a directory. I take it that this question means showing a list of only the directories and not other files under a certain location of your Unix filesystem.
Very quick tip for you today, I just see that many of visitors of this block are curious how they can find a directory in Unix – and so here’s a command to help you do just that.
When you’re trying to clean up your filesystems and reclaim some space, one of the first things you’ll want to do is to confirm the largest directories and individual files you have. This can be easily done using two Unix commands: find command and du command.
To some this may seem like a trivial task, but I see great interest from Unix/Linux beginners arriving to this blog: how exactly does one confirm what a symlink points to?
Upgrading Ubuntu 19.04 to Ubuntu 20.04
Ubuntu 20.04
It’s time to upgrade home servers, so I have finally gotten aroud to upgrading one system from Ubuntu 19.04 to Ubuntu 20.04
Before Attempting an OS Upgrade
I think it’s important to reiterate: just like with any other in-place major software or OS upgrade, make sure you have backups of your system and a plan to recover from them.
What I mean by having a plan is some basic considerations like:
can you boot that system from a different disk or USB stick?
do you have the install media prepared (and ideally - tested)?
once booted, might there be some issues accessing your old installation like distro mismatch or disk encryption?
do you have the root password? have you checked that it works? if system fails to boot, you will need it for single user mode
do you have password protected GRUB or BIOS password that you don’t necessarily remember anymore?
do you have access to the server console? if it’s a desktop, do you have a monitor and keyboard that will connect (do you have the right cables, will they match the ports you have on the system and do your cables actually reach that system if you urgently need to plug display in)
I hardly mention these lately, but can confirm that each one of these considerations helpd in a relevant scenario - not that long ago. Things like “DVD drive died” or “USB stick worked on 64bit but won’t boot on 32bit system” happen all the time - so it pays to spend 5-10min going through this list before kicking off the upgrade.
How To Upgrade Ubuntu 19.04 to 20.04
If you know Ubuntu Releases at all, you should remember that there’s usually another release between 19.04 and 20.04 - it’s 19.10.
All the x.10 releases are called interim releases - they’re issued about 6 months after each x.04 release and are not supported even for a full year. So you must upgrade very quickly from x.10 release to the next release available.
All the x.04 releases are LTS releases - Long Term Support. This means they’re usually good for a couple of years - fully supported with maintenance updates. For instance, 20.04 will be supported until late 2022 (at which stage the next LTS release 2022.04 will be available).
Before Any Ubuntu Release Upgrade
Be sure to fully update your current OS:
apt-get update
apt-get upgrade
shutdown -r now
Once these are done, you can progress to the OS upgrade
Upgrading to Ubuntu 19.10
I simply ran the do-release-upgrade command as root. See how it picked up the next release:
[email protected]:~ $ sudo -i
[email protected]:~ # do-release-upgrade
Checking for a new Ubuntu release
Your Ubuntu release is not supported anymore.
For upgrade information, please visit:
http://www.ubuntu.com/releaseendoflife
Get:1 Upgrade tool signature [1,554 B]
Get:2 Upgrade tool [1,329 kB]
Fetched 1,331 kB in 0s (0 B/s)
authenticate 'eoan.tar.gz' against 'eoan.tar.gz.gpg'
extracting 'eoan.tar.gz'
Reading cache
Checking package manager
Continue running under SSH?
This session appears to be running under ssh. It is not recommended
to perform a upgrade over ssh currently because in case of failure it
is harder to recover.
If you continue, an additional ssh daemon will be started at port
'1022'.
Do you want to continue?
Continue [yN] y
Starting additional sshd
To make recovery in case of failure easier, an additional sshd will
be started on port '1022'. If anything goes wrong with the running
ssh you can still connect to the additional one.
If you run a firewall, you may need to temporarily open this port. As
this is potentially dangerous it's not done automatically. You can
open the port with e.g.:
'iptables -I INPUT -p tcp --dport 1022 -j ACCEPT'
To continue please press [ENTER]
Reading package lists... Done
Building dependency tree
… after all the calculations I got the summary for the proposed upgrade - you get it before the download of all the packages starts:
10 installed packages are no longer supported by Canonical. You can
still get support from the community.
5 packages are going to be removed. 79 new packages are going to be
installed. 1092 packages are going to be upgraded.
You have to download a total of 955 M. This download will take about
4 minutes with your connection.
Installing the upgrade can take several hours. Once the download has
finished, the process cannot be canceled.
Continue [yN] Details [d]y
Fetching
Looked good, so I pressed y and continued.
It took about 30min to download and upgrade packages, and then I rebooted again.
Actually, then I tried to upgrade, but Ubuntu is smart enough to insist on a reboot before doing the next OS upgrade:
[email protected]:~ # do-release-upgrade
Checking for a new Ubuntu release
You have not rebooted after updating a package which requires a reboot. Please reboot before upgrading.
Upgrading to Ubuntu 20.04
Do a basic check of your system:
does it still boot fully
can you access your files
does it start the services you have configured?
And we can continue:
[email protected]:~ # do-release-upgrade
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [1,554 B]
Get:2 Upgrade tool [1,342 kB]
Fetched 1,343 kB in 0s (0 B/s)
authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg'
extracting 'focal.tar.gz'
Reading cache
Checking package manager
Continue running under SSH?
This session appears to be running under ssh. It is not recommended
to perform a upgrade over ssh currently because in case of failure it
is harder to recover.
If you continue, an additional ssh daemon will be started at port
'1022'.
Do you want to continue?
Continue [yN] y
Starting additional sshd
To make recovery in case of failure easier, an additional sshd will
be started on port '1022'. If anything goes wrong with the running
ssh you can still connect to the additional one.
If you run a firewall, you may need to temporarily open this port. As
this is potentially dangerous it's not done automatically. You can
open the port with e.g.:
'iptables -I INPUT -p tcp --dport 1022 -j ACCEPT'
To continue please press [ENTER]
Reading package lists... Done
Building dependency tree
and after a bit - the usual OS uprade summary. More than a thousand of packages will be upgraded, apparently:
Do you want to start the upgrade?
15 installed packages are no longer supported by Canonical. You can
still get support from the community.
5 packages are going to be removed. 111 new packages are going to be
installed. 1308 packages are going to be upgraded.
You have to download a total of 1,072 M. This download will take
about 5 minutes with your connection.
Installing the upgrade can take several hours. Once the download has
finished, the process cannot be canceled.
Continue [yN] Details [d]y
Fetching
Why I said You Need To Be Prepared
As luck would have it, this was the time when something went wrong. Perhaps I rebooted the server from another console, but it went down and they wouldn’t boot anymore - I forgot how tricky this 32bit/64bit mix of an mini-server this this is. It just wouldn’t boot anymore.
I had to reconnect my display/keyboard, boot into previous kernel and complete the upgrade:
[email protected]:~ # apt-get upgrade
E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem.
[email protected]:~ # sudo dpkg --configure -a
Setting up mousetweaks (3.32.0-2) ...
Setting up gnome-terminal (3.36.1.1-1ubuntu1) ...
Setting up gir1.2-gtksource-4:amd64 (4.6.0-1) ...
Setting up libgcr-ui-3-1:amd64 (3.36.0-2build1) ...
...
One more final reboot (shutdown -r now) and we’re sporting the Ubuntu 20.04 OS:
Ubuntu 20.04
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I'm a principal consultant with Tech Stack Solutions. I help with cloud architectrure, AWS deployments and automated management of Unix/Linux infrastructure. Get in touch!
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Ubuntu 20.04
It’s time to upgrade home servers, so I have finally gotten aroud to upgrading one system from Ubuntu 19.04 to Ubuntu 20.04
Ubuntu 20.04
