Applies To

• Linux
• ndctl utility

Issue

Executing the ndctl utility, with or without commands or options, returns the following missing library error:

# ndctl --versionndctl: error while loading shared libraries: libjson-c.so.2: cannot open shared obj

Cause

The issue could be caused by one of the following issues:

• The json-c package is not installed
• A version mis-match between the json-c and ndctl. More recent versions of json-c deliver libjson-c.so.4 rather than libjson-c.so.2.
• The json-c library is installed in a non-default location and the LD_LIBRARY_PATH environment variable needs to be updated.

Verify which libraries are missing from ndctl using the ldd utility and identifying libraries that are ’not found':

# ldd `which ndctl`
        linux-vdso.so.1 (0x00007ffc677c4000)
        libndctl.so.6 => /lib64/libndctl.so.6 (0x00007f31fca49000)
        libdaxctl.so.1 => /lib64/libdaxctl.so.1 (0x00007f31fc843000)
        libuuid.so.1 => /lib64/libuuid.so.1 (0x00007f31fc63c000)
        libjson-c.so.2 => not found
        libc.so.6 => /lib64/libc.so.6 (0x00007f31fc27d000)
        libudev.so.1 => /lib64/libudev.so.1 (0x00007f31fc057000)
        [...]

Solution

Verify that the json-c package is installed. For example, on Fedora use dnf info --installed json-c. If it is installed, information about the package will be displayed, eg:

# sudo dnf info --installed json-c
Installed Packages
Name         : json-c
Version      : 0.13.1
Release      : 2.fc28
Arch         : x86_64
Size         : 65 k
Source       : json-c-0.13.1-2.fc28.src.rpm
Repo         : @System
From repo    : updates
Summary      : JSON implementation in C
URL          : https://github.com/json-c/json-c
License      : MIT
Description  : JSON-C implements a reference counting object model that allows you
             : to easily construct JSON objects in C, output them as JSON formatted
             : strings and parse JSON formatted strings back into the C representation
             : of JSON objects.  It aims to conform to RFC 7159.

If the package is not installed, a message similar to the following will be returned:

# sudo dnf info --installed json-c
Error: No matching Packages to list

To install the json-c package if it is missing, use

# sudo dnf install json-c

To query the json-c package to identify the library version use the following:

# dnf repoquery -l json-c | grep libjson-c.so
Last metadata expiration check: 2:07:37 ago on Fri 06 Jul 2018 06:18:47 AM MDT.
/usr/lib64/libjson-c.so.4
/usr/lib64/libjson-c.so.4.0.0
/usr/lib64/libjson-c.so.4
/usr/lib64/libjson-c.so.4.0.0
/usr/lib/libjson-c.so.4
/usr/lib/libjson-c.so.4.0.0
/usr/lib/libjson-c.so.4
/usr/lib/libjson-c.so.4.0.0

Verify the LD_LIBRARY_PATH includes the location of libjson-c.so.*. Note: /usr/lib and /usr/lib64 are automatically included.

# echo $LD_LIBRARY_PATH
/usr/local/lib:/usr/local/lib64

If the package and LD_LIBRARY_PATH are correct, the version of ndctl will need to be updated. Using ndctl --version won’t work and will simply return “ndctl: error while loading shared libraries: libjson-c.so.2: cannot open shared object file: No such file or directory”.

If the ndctl utility was installed using the ndctl package from the operating system’s repository, update the package to the latest version. On Fedora:

# sudo dnf update -y ndctl

If the latest version within the package repository is old with no new versions available, download, compile, and install from source code. Detailed instructions can be found in the Installing NDCTL chapter.

If the ndctl utility was previously compiled and installed using source code, download the latest version from the ndctl GitHub repository, compile, and install. Detailed instructions can be found in the Installing NDCTL chapter.