cb-pgsql service fails to start with error "FATAL: could not open shared memory segment "/PostgreSQL.XXXXXXXXX": Permission denied"

Products

• Carbon Black EDR

Issue/Introduction

The postgres service (cb-pgsql) fails to start on an EDR primary node with the following error messages logged in the /var/log/cb/pgsql/startup.out file:

<DATE><TIME> EDT [(PID) @ ] FATAL:  could not open shared memory segment "/PostgreSQL.XXXXXXXXX": Permission denied
<DATE><TIME> EDT [(PID) @ ] LOG:  database system is shut down

Environment

• Carbon Black EDR: All Supported Versions
• Linux OS: All Supported Versions

Cause

Postgres service writes a file in the shared memory location /dev/shm that should be mounted to the tmpfs filesystem with full permissions for user root. Here is a working example:

Resolution

1. Validate the current permissions on the /dev/shm directory:

   ls -ld /dev/shm

2. If they do not match the correct permissions, update the permissions:

   sudo chmod 1777 /dev/shm

3. Check that /dev/shm is correctly mounted to the tempfs location:

   df -h /dev/shm

    

   1.  If not, remount it correctly. Here is an example:

      #Edit the fstab file
      sudo nano /etc/fstab
      
      # Locate the line related to /dev/shm and update it to the following:
      tmpfs /dev/shm tmpfs defaults,noexec,nodev,nosuid,size=2G 0 0
      
      #Remount the /dev/shm
      sudo mount -o remount /dev/shm
      (Or if you added security options, you can have them take immediate effect with: sudo mount -o remount,noexec,nodev,nosuid /dev/shm)
      
      

4. Restart the EDR services and validate cb-pgsql is able to successfully start.