While it shouldn’t happen when using the official apt-get repositories, if you download software off the Internet and run it then there’s a chance that you’ll see the dreaded bash: ./nameOfProgram: cannot execute binary file: Exec format error. This error, which is usually followed by bash: ./nameOfProgram.sh: Permission denied or something like it, indicates that Ubuntu wasn’t able to interface correctly with the binary you downloaded. This is because while it’s apparently a valid Linux binary, it’s designed for a different chipset than your kernel currently supports.
Most people using Ubuntu are on 32-bit or 64-bit processors based around a standard architecture that Intel released, regardless of who actually made their microchips. It’s important to remember that 64-bit processors can run in 32-bit mode, so if you’re getting this error even though you have a 64-bit processor there’s a chance you’re running a 32-bit version of Ubuntu. A few simple commands are all it takes to tell what your chip is operating as.
Method 1: Using the arch Command
If you’re not familiar with the type of microprocessor that you have installed on your machine, then you’ll first want to use the arch command from the command line. You’ll only see a single line of output returned to you after running this command. In many cases, you’ll see i686, which means that you’re on a 32-bit processor and therefore can’t run x86_64 binaries. If you instead see amd64 or something similar, then you’re on an x86_64 processor, and should at least theoretically be able to run most 32-bit and 64-bit binaries. Unlike Microsoft Windows, Ubuntu Linux actually contains the proper tools to permit users of 644-bit chipsets to run 16-bit Windows programs in their operating system in many cases as well.
These terms are still true even if you’re not actually using that particular model of microchip. For instance, i686 is how Linux refers to many 32-bit processors even if they aren’t actually Intel 80686 chips. Even if you’re using 64-bit Intel technology, arch might still call your processor an amd64 chip. This doesn’t indicate an error, and can be safely ignored. You can use cat /proc/cpuinfo or more /proc/cpuinfo to find out the exact type of processor you’re using. Since the lines in this file are long, you might want to push F11 before issuing it if you’re using a graphical terminal window. Users of a virtual console, especially those working with Ubuntu server, won’t have to worry quite as much.
You may see some other types of output, which might further restrict your options when it comes to running software. Ubuntu supported PowerPC architecture for the longest time, which is found in some workstations as well as many Classic Macintosh and older OS X Macintosh machines. You can actually still find Ubuntu repositories for these architectures, though they receive little support today. However, you more than likely won’t be able to run many Linux binaries you download from the Internet outside of the official repositories in this case. That doesn’t mean that Ubuntu doesn’t work on these machines, though you may want to look at the lighter Lubuntu distribution.
Method 2: Using the file Command
The file command identifies what different files contain, and it’s usually very accurate. Try identifying the file in question by typing file nameOfProgram to see if you get ELF 32-bit or ELF 64-bit as output. If it tells you that it’s an ELF 64-bit binary and you received i686 as output from the arch command, then there’s no way you can reasonably run it on your machine. If you’re on a 64-bit microprocessor running 32-bit Ubuntu, then you could technically reinstall the operating system, though this is a bit of an extreme step in order to run a single program.
There is also the very real possibility, however slight, that you might instead come across a binary that when you attempt to run it spews out junk characters to the terminal even if you’ve run a malware scan on it. These characters usually take the form of either lozenge-shaped blocks, or alternatively rectangular cubes that have numerical values in them. Some computer scientists call the latter tofu, and represent the Unicode values of characters that your currently installed typefaces won’t be able to display. If the terminal is displaying them like this, then you can rest assured that this is neither a font error nor anything having to do with malware. Rather, this is simply because the compiled microprocessor opcode inside of the binary is so alien to your system that it doesn’t know how to interpret some of the code.
The best way to fix this is to install the proper package for your architecture. If you’re installing packages from inside Ubuntu, then the apt-get system or the graphical Synaptic manager has you covered without any problems. If you’re downloading packages from another distribution, then you’ll need to find the right one for your architecture. Take, for example, Arch Linux’s listing of the gvim package. While the default package features the x86_64 architecture, there’s also one for the i686 chipset. This one will work on 32-bit machines that work with the Intel interrupt structure, but remember that the terms i686 and 32-bit are not mutually inclusive all the time since other chipsets Linux supports actually do feature their own 32-bit implementations.
Users exploring the whole GNU/Linux scene might come across binaries compiled for far more exotic technologies than these. Linux is truly a cross-platform code scene, so you’ll see OpenRISC, MIPS, SPARC, M32R, MN103, ARM, ARC, Alpha and many other standards binaries are compiled to work with. More than likely, you won’t be able to run any of these, though ARM is an extremely popular tablet and smartphone platform. It’s also the platform that the Raspberry Pi is based around, which means if you’re actually running Ubuntu on a mobile device or the Ubuntu MATE distribution for Raspberry Pi you’ll actually need these instead of Intel 32-bit or x86_64 binaries.