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.
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.
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.
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.
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:
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.
You probably know that modern Linux distributions have many things in common. Well, one of the reasons for this is LSB – Linux Standard Base. LSB is a joint project by a number of Linux vendors to standardize the OS environment.
The goal of the LSB is to develop and promote a set of standards that will increase compatibility among Linux distributions and enable software applications to run on any compliant system. In addition, the LSB will help coordinate efforts to recruit software vendors to port and write products for Linux.
One of the immediate benefits of LSB compliancy is ability to confirm the exact information about your Linux release using the lsb_release command. By exact information I mean the release version, vendor name and most interestingly the codename of your current Linux release.
visudo is a tool for safely updating the /etc/sudoers file, found in most Linux systems (Ubuntu for example).
Here's what the Ubuntu man page says about it, I think it's a great summary:
visudo edits the sudoers file in a safe fashion, analogous to vipw(8). visudo locks the sudoers file against multiple simultaneous edits, provides basic sanity checks, and checks for parse errors. If the sudoers file is currently being edited you will receive a message to try again later.
Attention: due to the sensitive content of the /etc/sudoers file, you can only run visudo as root.
If you run your Ubuntu system behind a firewall and have to use proxy server for http and ftp access, then your apt-get on a newly installed Ubuntu system will probably not work.
To make it use proxy, simply set the http_proxy environment variable. Once you get it working (try something like apt-get update), you'll probably want to add it to your .bashrc file.
If you have used your fresh Ubuntu install for longer than half an hour, chances are that you've discovered the sudo command already.
sudo allows certain users to execute a command under another user's privileges. Most commonly, using sudo implies running a command as a superuser, but the approach works equally well for allowing you to inherit a user ID (uid) and group ID (gid) of any user on the system.
To gain access, a password is asked, and by default it is your password, and not the password of a user you're trying to run a command as. This allows for the system' s administrator to effectively manage user privileges without having any user share their password.