Entries Tagged 'Ubuntu' ↓

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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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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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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 tried installing or upgrading Ubuntu recently, you probably noticed that all the storage devices are now using UUID – Universally Unique IDentifiers. I'm not claiming to know everything there is to know about UUIDs, but have become quite comfortable managing them lately, so hopefully this post will help you achieve the same.

What is a UUID exactly?

UUID is a Universally Unique IDentifier. It's a identification code given to each storage device you have on your system, aimed to help you uniquely identify each device no matter what.

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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.

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Many software products, especially the commercial ones, are distributed as 32-bit packages. This means that they won't be installed on your 64-bit system unless you clearly specify that you want to override the architecture dependency.

If you're using Ubuntu or any other Debian based distribution, this post will teach you how to install 32-bit deb packages on your 64-bit OS.

Is it possible to run 32-bit applications on 64-bit OS?

In Unix world, yes: it is quite possible to run 32-bit binaries on 64-bit OS. There should generally be no problem, but there are, as always, a few caveats:

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I see that my Finding Large Files and Directories post is quite popular, yet there are a few more ways to simplify your search for the largest disk space consumers in your Unix system.

Make find command show file sizes

If you remember, the default way a find command reports results includes only the fully qualified (that means including the full path) filenames.

Now, if you look at a task of identifying the largest files, it's great if you can get a list of all the files bigger than some figure your specify, but what would be even better is to include the exact size of each file right into the output of the find command.

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