Entries Tagged 'Linux' ↓

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SSH (Secure SHell) is possibly the best way to remotely access a Unix system – it's very secure thanks to automatic encryption of all the traffic, and it's also quite universal because you can do all sorts of things: access remote command line shell, forward graphics session output, establish network tunnels and set up port redirections. Today I'm going to show you how to get started with SSH in Ubuntu.

Installing SSH server in Ubuntu

By default, your system will have no SSH service enabled, which means you won't be able to connect to it remotely using SSH protocol (TCP port 22). This means that installing SSH server will be one of the first post-install steps on your system.

The most common SSH implementation is OpenSSH server, and that's exactly what you want to install.

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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.

Some of you probably remember the uname command which also shows you similar information, but uname confirms the running kernel of your OS and not the CPU capability: if you're booted into 32bit mode, it will not help you to recognize the 64bit potential of your system.

Obtaining CPU information from /proc/cpuinfo

Most Linux distros will have the special /proc/cpuinfo file which contains a textual description of all the features your processors have. This is a very useful file – depending on your task it may help you identify any features of your processors, as well as confirm the overall number of CPUs your system has installed.

Most commonly, the following information is obtained from /proc/cpuinfo:

• processor model name and type
• processor speed in Mhz
• processor cache size
• instruction flags supported by CPU

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Hi everyone, I'm finally back from my holidays, and simply cannot wait to share some more Unix tips with all of you!

Today I'll talk a bit more about yet another way of learning version information about your Linux OS: the /proc/version file. I mentioned it briefly in one of the previous posts, but would like to finish the explanations.

What you can learn from /proc/version

This file will not show you the name of the actual OS release, but will instead give you specifics about the version of Linux kernel used in your distribution, and confirm the version of a GCC compiler used to build it.

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Hi all, today I'm going to teach you not one, but two really cool things in one post! First, I'll introduce you to advanced memory usage stats available on Linux systems through /proc/meminfo file, and then I'll explain the basics of using the watch command.

Memory usage with /proc/meminfo

As you know, quite a few Unix-like systems use the so-called pseudo file systems like /proc. It's not a real filesystem, but just a convenient representation of processes managed by your Unix OS. In Linux systems, this directory also contains quite a few files allowing you to access various information about your system. /proc/meminfo is one of such files, it gives you access to most of the memory usage stats.

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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.

File ownership in Unix

Just to give you a quick reminder, I'd like to confirm that every single file in Unix belongs to some user and some group. There simply isn't a way to create a file without assigning ownership. I've briefly touched the topic of confirming file ownership in Unix before, so today I will simply build on that and show you how to change ownership of files.

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I've been upgrading Ubuntu installations quite a few times recently, and thought it makes sense to post a really short how-to if you ever want to upgrade your Ubuntu distro from the command line.

Use apt-get to upgrade Ubuntu

The procedure for upgrading one Ubuntu release to another one is pretty straightforward. There are some rules though:

1. Never attempt to skip a release or two when upgrading
2. Never do a few Ubuntu release upgrades in a row without reboots in between
3. Always backup the files you change
4. Always have an install CD for your current Ubuntu release around

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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.

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In my first introductory rsync post, How To Synchronize Directories with Rsync, I've shown you the most basic approach to syncing two directories up. Today, I'd like to show you another useful thing you can do with rsync.

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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.

How packages information is stored in Ubuntu

Essentially being a fork of the Debian Linux, Ubuntu inherited quite a lot of things from it. One of them is the way packages are installed and managed.

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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.

free – free and used memory stats

free command is the most obvious choice for a first command when it comes to your RAM.

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