Why does CageFS remount fix an issue if CageFS is not the root cause?

Issue

Running the following command resolves an issue temporarily or immediately:

cagefsctl --remount-all

However, CloudLinux Support may still state that CageFS was not confirmed as the root cause.

Environment

• CloudLinux OS 
• CageFS 
• LVE 
• cagefsctl 
• Servers where CageFS is enabled for users

Solution

cagefsctl --remount-all performs several operations at once. Because of this, a successful remount can confirm that the issue was cleared after the remount, but it does not confirm which exact operation fixed the issue.

During a CageFS remount, the system may perform actions such as:

1. Check common binary directories with ldd and add required dependencies to CageFS
2. Restart the proxyexec service
3. Unmount the current CageFS skeleton
4. Mount the CageFS skeleton again
5. Recreate LVE namespaces
6. Stop processes running inside existing LVE namespaces
7. Create new LVE namespaces with limits reset to their configured values
8. Mount the CageFS skeleton and users’ personal directories into the users’ LVE namespaces

Since several components are refreshed during the same operation, it is not possible to determine from the remount result alone whether the issue was caused by:

• CageFS mount state
• Missing or refreshed dependencies
• proxyexec
• LVE namespace state
• Processes running inside the previous LVE namespace
• Another temporary condition cleared during the remount

For this reason, CageFS remount can be used as a troubleshooting or recovery action, but it should not be treated as root cause confirmation by itself.

Cause

CageFS remount is a broad refresh operation. It does not only rebuild or remount CageFS. It also affects related runtime components, including LVE namespaces and processes running inside them.

If the issue disappears after the remount, the result shows that one of the actions performed during the remount cleared the symptom. Additional investigation is required to confirm the original cause..

Useful Links

• https://cloudlinux.zendesk.com/hc/en-us/articles/8955430586908-What-is-CageFS 
• https://docs.cloudlinux.com/cloudlinuxos/cloudlinux_os_components/#cagefs 
• https://docs.cloudlinux.com/cloudlinuxos/cloudlinux_os_components/#lve-stats-2