When you encounter the "Failed to initialize NSS library" error during yum operations on RHEL 7.7.3, it typically stems from corrupted NSS libraries or mismatched Python modules. The specific error message about being unable to "import name ts" indicates a deeper Python dependency issue.

First, verify your current Python environment with:

python --version
rpm -qa | grep python-nss

On RHEL 7.7.3, you should see Python 2.7.5 and python-nss-0.16.0 or later. If these versions don't match, we've found our problem source.

1. Reinstall NSS Packages

sudo yum remove nss nss-util nss-sysinit nss-tools
sudo yum clean all
sudo yum install nss nss-util nss-sysinit nss-tools

2. Fix Python-NSS Binding

The critical step is reinstalling the python-NSS bindings:

sudo rpm -e --nodeps python-nss
sudo yum install python-nss

3. Verify Library Paths

Check if NSS libraries are properly linked:

ls -l /usr/lib64/libnss3.so
ldconfig -p | grep nss3

If links are broken, recreate them:

sudo ln -sf /usr/lib64/libnss3.so /usr/lib64/libnss3.so.1d

If the issue persists, manually verify the Python module integrity:

python -c "import NSS; print(NSS.__file__)"

This should output:

/usr/lib64/python2.7/site-packages/NSS/__init__.py

If not, force reinstall all dependencies:

sudo yum reinstall python python-libs python-nss

To avoid future occurrences:

• Regularly update all packages: sudo yum update
• Maintain consistent Python environments
• Avoid manual library modifications

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When working with RHEL 7.7.3 systems, you might encounter this frustrating error during package updates:

error: Failed to initialize NSS library
There was a problem importing one of the Python modules required to run yum.
The error leading to this problem was: cannot import name ts

This error typically occurs due to a mismatch between:

• Python NSS bindings (python-nss)
• The system's NSS library version
• Yum's dependencies

First, verify your current Python and NSS versions:

python -V
rpm -q nss nss-util nss-sysinit nss-tools

Here's the most reliable fix sequence:

# Reinstall critical components
sudo yum clean all
sudo rpm -e --nodeps nss nss-util nss-sysinit nss-tools
sudo yum install nss nss-util nss-sysinit nss-tools python-nss

If you encounter dependency issues, try forcing the reinstallation:

sudo rpm -Uvh --force /var/cache/yum/x86_64/7Server/nss-*.rpm

For systems where the standard fix doesn't work:

# Backup first
sudo cp /usr/lib64/python2.7/site-packages/nss/__init__.py{,.bak}

# Modify the Python NSS binding
sudo sed -i 's/from _nss import \*/from _nss import \*, ts/' /usr/lib64/python2.7/site-packages/nss/__init__.py

After applying fixes, test with:

python -c "import nss; print(dir(nss))" | grep ts
yum check-update

To avoid similar issues:

• Regularly update all packages: sudo yum update -y
• Maintain consistent versions of security libraries
• Monitor Red Hat's errata for NSS updates

Consider these nuclear options:

# Rebuild yum cache
sudo rm -rf /var/cache/yum/*
sudo yum clean all
sudo yum makecache

# Worst case - reinstall yum
sudo rpm -e yum yum-metadata-parser python-urlgrabber
sudo yum install yum yum-utils