Turning off shared libraries is a common task for many computer users. Shared libraries allow multiple programs to access the same libraries or code, reducing duplication and saving disk space. However, sometimes you may want to disable shared libraries for troubleshooting purposes or to isolate program behavior. Here are some quick answers on how to turn off shared libraries on the major operating systems.
Quick Answers
To turn off shared libraries on:
- Windows – Disable the Dynamic-Link Library Search Order service
- Mac – Unset the DYLD_LIBRARY_PATH environment variable
- Linux – Use the –disable-new-dtags option for the linker, or set the LD_LIBRARY_PATH environment variable to an empty value
Disabling shared libraries can prevent programs from loading required code libraries and cause them to crash or exhibit odd behavior. Only do this for troubleshooting purposes and make sure to re-enable afterwards.
What are Shared Libraries?
Shared libraries, also known as dynamic link libraries or DLLs on Windows, are collections of code that can be shared between multiple programs. They help reduce duplication of code across programs since the programs can share the same library files on disk. This saves disk space since the library code only needs to exist in one place on the system.
Shared libraries also facilitate updates and bug fixes – when a fix or patch is released for a shared library, all programs using that library will benefit from the update since they use the same shared files. Libraries allow code changes to be deployed across many applications simultaneously.
Common examples of shared libraries include system libraries used by many programs, like standard C/C++ runtime libraries, graphical interface libraries like GTK+ or Qt, or other utility code and frameworks.
Advantages of Shared Libraries
- Reduce duplication – code exists in only one place
- Save disk space – programs share the same files
- Ease deployment of updates – bug fixes and updates apply across all programs using the library
- Modularization – libraries group functionality and abstract away implementation details
Disadvantages of Shared Libraries
- Versioning issues – programs may require specific library versions
- Dependency issues – programs may fail if dependent libraries are missing
- Namespace conflicts – symbols or identifiers shared across libraries
- Performance overhead – lookups required to find symbols in shared libraries
Why Disable Shared Libraries?
In most cases, you want to keep shared libraries enabled so programs can access the code they need to function properly. However, there are some specific troubleshooting scenarios where temporarily disabling shared libraries can help isolate a problem:
- Determining dependency issues – Disabling shared libraries can quickly reveal if a program depends on a particular library to run properly.
- Pinpointing code problems – Forcing a program to use its own private copies of libraries rules out issues being caused by another program’s libraries.
- Checking for namespace conflicts – Symbols like function names shared across libraries can sometimes cause conflicts.
- Improving security – Potentially risky or vulnerable shared code can be disabled as a precaution.
- Analyzing performance – Program speed may improve by using private instead of shared libraries.
In most cases, shared libraries should only be disabled temporarily for testing and troubleshooting. Permanently disabling shared libraries negates their disk space and maintenance advantages. Specific programs relying on libraries may also fail to operate properly with libraries disabled.
How to Disable Shared Libraries on Windows
On Windows, shared code libraries are called dynamic-link libraries (DLLs). The DLL search order controls how Windows locates DLLs for programs.
To disable shared DLL usage on Windows:
- Open the Local Group Policy Editor by running
gpedit.msc - Navigate to Computer Configuration > Administrative Templates > System > Load DLL Function
- Double click on Turn off Dynamic-Link Library Search Order randomization
- Select Enabled and click OK to disable DLL search order randomization
- Shutdown and restart the computer for changes to take effect
This prevents Windows from randomizing the order DLLs are searched for each program invocation. Programs will attempt to load DLLs from their own folder before searching system paths. This isolates programs from potentially using the same shared DLLs.
Alternatively, you can use a tool like Process Monitor to watch a specific process and see which DLLs it attempts to load. You can then selectively rename, move, or remove shared DLLs that you want to isolate from the process.
Implications of Disabling DLL Sharing in Windows
With DLL sharing disabled, programs will consume more memory and disk space since private copies of DLLs need to be loaded. Programs may also fail to operate properly if they can’t find required DLL dependencies.
Make sure to re-enable DLL sharing once troubleshooting is complete. Leaving it permanently disabled negates the benefits of shared libraries in Windows and can lead to system instability.
How to Disable Shared Libraries on Mac
On macOS and other Unix-based systems, shared libraries have a .dylib file extension. The DYLD_LIBRARY_PATH environment variable controls the search path for locating shared libraries.
To disable shared libraries on Mac:
- Open Terminal
- Enter:
unset DYLD_LIBRARY_PATH - Launch the program you want to isolate – it will now only use its private bundled libraries
Alternatively, you can launch the program directly from Terminal and pass -Wl,-bundle_loader to force private bundling of libraries:
./MyProgram -Wl,-bundle_loader
Implications of Disabling dylib Sharing on Mac
Like on Windows, removing access to shared libraries will cause increased memory usage and disk consumption as private copies of libraries need to be loaded into each program.
Dependency issues may also occur if the program expects to find a particular library version on the system paths. Thoroughly test applications after disabling shared library usage.
How to Disable Shared Libraries on Linux
On Linux systems, shared libraries use the .so extension. The LD_LIBRARY_PATH environment variable controls the shared library search path, similar to Mac.
To disable library sharing on Linux:
- Open a terminal window
- Enter:
export LD_LIBRARY_PATH= - Launch your program – it will now only use its private libraries
You can also compile programs with the --disable-new-dtags option to force static linking and bundling of all required libraries:
gcc -Wl,--disable-new-dtags myprogram.c -o myprogram
Implications of Disabling .so Library Sharing on Linux
The considerations are similar on Linux as on Mac and Windows – increased memory usage, disk space, risk of dependency issues, etc. Thoroughly validate program behavior after disabling shared libraries.
Make sure to revert changes by resetting LD_LIBRARY_PATH and rebuilding programs without --disable-new-dtags when done troubleshooting.
Other Methods for Isolating Shared Libraries
In addition to completely disabling shared library usage, there are some other options for isolating and troubleshooting library problems:
- Copy shared libraries to a program’s folder to force private local use
- Rename/move conflicted libraries so programs load non-conflicting versions
- Use tracing tools like strace or DTrace to log library calls from programs
- Set library environment variables to known/stable library paths to control version used
- Run programs in containers or virtual machines to contain library changes
Adding library folders earlier in system paths can also force usage of specific library versions before others. Overall, be very careful when making changes to shared libraries – thoroughly test program behavior afterwards.
Conclusion
Disabling shared libraries can help troubleshoot dependency issues, namespace conflicts, performance problems, and other code behavior. However, it negates the benefits of shared libraries so should only be done temporarily.
Carefully isolate and test applications after disabling shared libraries. Impacts include increased memory and disk usage due to private copies of libraries needing to be loaded. Programs may also fail with missing dependency errors.
Make sure to re-enable shared library support once testing is complete. Leaving it permanently disabled can lead to system instability and performance degradation over time.