linux-unix

recent posts related to linux and unix

How to easily determine the blocksize of a filesystem

I just saw that this is a way you can easily determine the blocksize of a filesystem, at least a Mac/Unix/Linux filesystem:

$ echo foo > foo

$ du -h foo
4.0K    foo

I tried to do the same thing with touch foo, but that didn’t work. Without digging into it more, the key seems to be in having very little text in the file, at which point the du command shows the minimum block size for the file.

A large collection of Unix/Linux ‘find’ command examples

Linux/Unix FAQ: Can you share some Linux find command examples?

Sure. The Unix/Linux find command is very powerful. It can search the entire filesystem to find files and directories according to the search criteria you specify. Besides using the find command to locate files, you can also execute other Linux commands (grep, mv, rm, etc.) on the files and directories you find, which makes find extremely powerful. 

How to use the Linux ‘scp’ command without a password to make remote backups

Summary: How to create a public and private key pair to use ssh and scp without using a password, which lets you automate a remote server backup process.

Over the last two years I've ended up creating a large collection of websites and web applications on a variety of Linux servers that are hosted with different companies like GoDaddy and A2 Hosting. I recently embarked on a mission to automate the backup processes for all these sites, and as a result of this effort, I thought I'd share what I've learned here.

A large collection of Unix/Linux ‘grep’ command examples

Linux grep commands FAQ: Can you share some Linux/Unix grep command examples?

Sure. The name grep means "general regular expression parser", but you can think of the grep command as a "search" command for Unix and Linux systems: it's used to search for text strings and more-complicated "regular expressions" within one or more files.

I think it's easiest to learn how to use the grep command by showing examples, so let's dive right in.

Unix find command: How to move a group of files into the current directory

I just bought a bunch of MP3 music files from Amazon, and when I downloaded the zip file they provide onto my Mac, it was a bunch of files in a bunch of subdirectories; not really convenient to work with when you’re trying to import them into iTunes. So I used this Unix find command to move all of the music files from the subdirectories they were scattered in into the root directory that was created when I expanded the zip file:

cd Amazon-Music-Folder
find . -type f -exec mv {} . \;

If you ever need to either copy or move a bunch of files with a single command, I hope this example shows the correct find command syntax for your needs. (If you need to copy the files, use the cp command instead of the mv command.)

How to reset the MySQL root password on an Ubuntu server

As a brief note to self, if you forget the MySQL root password again, these are the steps you followed to create a new MySQL root password on an existing MySQL server running on Ubuntu 16.x:

How to use ‘awk’ to print columns from a text file (in any order)

One of my favorite ways to use the Unix awk command is to print columns of information from text files, including printing columns in a different order than they are in in the text file. Here are some examples of how awk works in this use case.

How to set and use a vim color scheme

In an earlier vim color configuration tutorial I described how to have fine-grained control of your vi and vim color settings. In this article I’ll take an easier route and just show how you can use existing color schemes in your vi editor sessions.

Using a vim color scheme

Using a vim color scheme is actually pretty simple. If you’re in a vim editor session, just issue the vim colorscheme command from last line mode, like this:

My vi/vim tutorial goes over 200,000 views

Way back when I lived in this low-income apartment complex in Wasilla, Alaska — technically I had no income at the time, and it’s ridiculously hard to find a place to live in Alaska in the summer — and spent as much time as I could meditating in the mountains, I created a vi/vim editor video tutorial and put it on YouTube. I just noticed that video has now exceeded 200,000 views. It feels a little weird to think that over 200K people have started to learn vi/vim from that video.

A funny thing about making that video is that the walls in that apartment complex were paper-thin. I could hear everything my neighbors did in their apartments (use your imagination and you won’t be wrong), and they could hear me, so I intentionally tried not to talk too loud in the video. I had to edit the video at several points to crop out some of my neighbors yelling at each other.

Format of the Linux crontab date and time fields

I’ve written several things about the Linux cron command and crontab file format before, and as a quick note, here’s some information on the format of the crontab date and time fields.

Crontab date/time fields

First, from the crontab man page documentation: