Now’s my first year at university.
We’re given credentials so we can login into the computers around the campus, which run Ubuntu 12.04 LTS and —surprise!— have not been updated in a whole lot of time.
After using them for some time, the unevitable happened: It lacked my essential set of programs (Chromium or Node.JS or KmPlot for example) and I really
missed my laptop where I have admin rights and I can just apt-get install what I need. These computers boot via PXE, so I thought about bringing a Pi
to make them boot whatever I wanted, but it’d be a questionalbly legal approach which could get me into trouble.
I don’t want that. (Not yet.)
So I’m making this series of posts explaining the steps I did to get a bit of freedom within my restricted user, in the hope they’ll be useful for someone else.
Spoiler: I could finally run my own, sandboxed Debian install inside my user, with great results! This is explained in the next parts.
First steps
Let’s start with the basics. You don’t have root access so you can’t install binaries at /usr/bin; you need a directory that is always in PATH, where you can drop programs and run them as if they were system-wide commands.
mkdir -p ~/.local/bin
In case you didn’t know, there’s a convention that .local is like the /usr/local prefix but for individual users (/usr/local/share is equivalent to ~/.local/share, same with bin, lib, …). We’ll be following this convention.
Now, edit ~/.profile and append the code:
export PATH=$PATH:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:$HOME/.local/bin
This will add our directory to PATH as well as the sbin directories where commands like ifconfig are stored.
Important: add it to
.profile, not.bashrc. The earlier is session-wide, the latter only applies to your interactive Bash shells.
And while we’re at it, what about having our own directory for libraries as well? Maybe our programs depend on libraries which are not installed. So let’s do it:
mkdir -p ~/.local/lib
Edit ~/.profile and append:
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/.local/lib
Now the linker will also load libraries from our local directory.
Great! Logout and login again to make changes effective.
Installing packages
Now to something more interesting: installing .deb packages. Let’s suppose we want to install the tree utility.
apt-get install tree won’t work of course, but we can instead do apt-get download tree, which will just fetch the .deb package from the repos.
Then let’s extract the contents of the package in some directory:
mkdir test
dpkg-deb -x tree_xxxxx_xxxx.deb test
# repeat for every downloaded package
It’ll create a bunch of files in test/usr/share (documentation and manual pages), and the binary that we want at test/usr/bin/tree.
So we can take that binary and drop it in .local/bin and we should be able to run tree without problems now.
What if I can’t?
That’s probably because, in order for tree to run, you must install some dependencies too.
Try to simulate how apt-get would install that package:
apt-get -s install tree
Note the dependencies apt-get installs, and repeat the procedure above for each dependency.
Remember to copy any library you see to .local/lib!
Compiling programs
Now, what if we want to install a program that isn’t on the repos, or you want to install a newer version? I’d recommend you do something very similar to what we did above.
Compile it as you’d do on your computer (i.e. ./configure && make or whatever it needs) but don’t do the final make install since we don’t have root access.
Instead, create an empty directory and tell make to install the files there:
mkdir test
DESTDIR=test make install
Examine the files it installed, and copy what you need to the local directories as we did in the previous section.
Even if the program doesn’t use make as buildsystem, you should still try to invoke it with the DESTDIR variable set, as we did before.
It’s a pretty standard convention. If it still doesn’t work, just copy the files yourself and see if it works.
Conclusion
We’re still limited, but we can at least install our own programs now.
But there must be a better way…
This comes at part II!