Linux Tutorials

5 Simple Steps to Find Any Shared Library (2025 Guide)

Tired of the 'error while loading shared libraries' message? Our 2025 guide provides 5 simple steps using ldd, ldconfig, and more to find any missing .so file.

David Miller

A Linux systems engineer and open-source enthusiast with over a decade of experience.

September 8, 20257 min read13 views

If you’ve spent any time on a Linux or Unix-like system, you’ve probably met this dreaded message:

error while loading shared libraries: libsomething.so.1: cannot open shared object file: No such file or directory

It’s a frustrating roadblock that can stop an application dead in its tracks. You know the program is installed, but it can’t find a critical component it needs to run. That component is a shared library, a piece of reusable code that multiple programs can use simultaneously.

But here’s the good news: finding that missing library is almost always a straightforward process. Forget guesswork and random searching. This 2025 guide will walk you through five simple, systematic steps to locate any shared library on your system. Let's dive in.

Step 1: Start with `ldd` — The Quickest Check

Before you go on a digital scavenger hunt, let the system tell you exactly what it’s looking for. The ldd (List Dynamic Dependencies) command is your best first stop. It examines an executable file and prints out every shared library it needs, along with the path where the system expects to find it.

To use it, simply point it at the program that’s failing:

ldd /usr/local/bin/my_cool_app

You’ll get an output that looks something like this:

    linux-vdso.so.1 (0x00007ffc5b3d9000)
    libssl.so.1.1 => /usr/lib/x86_64-linux-gnu/libssl.so.1.1 (0x00007f5a9c9f8000)
    libcrypto.so.1.1 => /usr/lib/x86_64-linux-gnu/libcrypto.so.1.1 (0x00007f5a9c709000)
    libcustom.so.2 => not found
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f5a9c517000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f5a9cadb000)

The format is library_name => path_to_library. See that "not found" line? That’s our culprit. The program my_cool_app needs libcustom.so.2, but the dynamic linker can't find it in any of its configured locations. Now we have a specific target: libcustom.so.2. This one command often solves 90% of the mystery.

Step 2: Check the Standard Library Paths

The dynamic linker doesn't scan your entire hard drive every time you run a program—that would be incredibly slow. Instead, it looks in a few standard, pre-defined directories. These are the most common places to find system-wide libraries.

The primary locations are:

/lib
/usr/lib
/lib64 (on 64-bit systems)
/usr/lib64 (on 64-bit systems)

You can do a quick check to see if your missing library (or a similar version) exists in one of these folders. Using the find command is perfect for this, as it can search multiple directories at once.

find /lib /usr/lib /lib64 /usr/lib64 -name "libcustom.so*"

The asterisk (*) is a wildcard that helps find files even if they have version numbers appended, like libcustom.so.2.5. If this command returns a path, you’ve found the library! The question then becomes why the system isn’t seeing it, which we’ll cover in the final section.

Step 3: Query the `ldconfig` Cache

To speed things up, Linux maintains a cache file (/etc/ld.so.cache) that contains a compiled list of all the libraries found in the trusted directories. The ldconfig utility is used to manage this cache.

You can use ldconfig to print the cache and then filter it with grep to see if your library is listed. This is a very fast and effective way to check what the system officially knows about.

ldconfig -p | grep libcustom

The -p flag tells ldconfig to print the current cache. If your library is known to the system, you’ll see output like this:

    libcustom.so.2 (libc6,x86-64) => /opt/custom_app/lib/libcustom.so.2
    libcustom.so (libc6,x86-64) => /opt/custom_app/lib/libcustom.so

Pro Tip: If you just installed a new library from source or with a package manager and it’s not being found, your cache might be out of date. You can force a rebuild of the cache by running:

sudo ldconfig

Running this one command is a surprisingly common fix for "library not found" errors after a new installation.

Step 4: Inspect the `LD_LIBRARY_PATH` Environment Variable

Sometimes, libraries aren’t installed in standard system directories. This is common for software installed in a user's home directory or in a custom location like /opt. For these cases, there's a special environment variable: LD_LIBRARY_PATH.

This variable contains a colon-separated list of extra directories where the linker should look for shared libraries. It's checked before the standard paths and the cache.

First, see if it’s already set:

echo $LD_LIBRARY_PATH

If it's empty, nothing will be printed. If it's set, you'll see something like /opt/myapp/lib:/usr/local/otherapp/lib. You should check if your missing library exists in any of those custom directories.

While useful for development and temporary testing, relying on LD_LIBRARY_PATH for system services is often discouraged because it can make application behavior dependent on a user's shell environment. However, it's a fantastic tool for a quick fix. If you find your library in, say, /opt/custom_app/lib, you can run your program like this:

LD_LIBRARY_PATH=/opt/custom_app/lib ./my_cool_app

If the program runs, you've confirmed the library's location and that LD_LIBRARY_PATH is a valid way to point to it.

Step 5: The Ultimate Search with `find` and `locate`

If the steps above come up empty, it’s time to search the entire filesystem. This is your last resort, but it’s a definitive one. You have two main tools for this job: find and locate.

Using `find`

The find command searches the filesystem in real-time. It's thorough but can be slow on large disks.

sudo find / -name "libcustom.so*" 2>/dev/null

sudo is important for searching protected system directories.
/ tells it to start from the root directory.
-name "libcustom.so*" searches for the file by name, using a wildcard.
2>/dev/null is a handy trick to hide all the "Permission denied" errors, keeping your output clean.

Using `locate`

The locate command is much faster. It searches a pre-built database of all files on the system. The only downside is that the database can be out of date if you recently added the file.

locate libcustom.so

If you suspect the database is stale, you can update it with:

sudo updatedb

If either find or locate returns a path, you have definitively found your file.

What To Do When You Find It (The Permanent Fix)

Finding the file is only half the battle. Now you need to tell the system where it is permanently. Let's say you found libcustom.so.2 in /opt/custom_app/lib.

You have a few options, but here is the best one for a system-wide fix:

Add a new configuration file to /etc/ld.so.conf.d/. This is the modern, clean way to add a permanent library path. Simply create a new file (e.g., custom_app.conf) in that directory:

# Create and open the file with a text editor
sudo nano /etc/ld.so.conf.d/custom_app.conf

Inside that file, add the path to the directory containing your library:

/opt/custom_app/lib

Save the file, then run sudo ldconfig to rebuild the cache. The linker will now be aware of this new directory, and your application should run without any issues.

Conclusion

That "cannot open shared object file" error doesn't have to be a showstopper. By following these five logical steps—from the quick check with ldd to the comprehensive search with find—you can systematically diagnose and solve the problem every time. Once found, a simple configuration change is all it takes to get your application back up and running.

What other common Linux debugging challenges do you face? Share your thoughts and questions in the comments below!