This article explains the meaning and impact of the recurring log message observed on Juniper MX routers involving FPCs:

Child exit [phys_mem_size > /var/log/phys_mem_size.out].

These messages are related to log rotation and are generally non-critical.

Repeated log entries in the messages file, similar to:

%PFE-3: fpc8 ERROR Child exit [phys_mem_size > /var/log/phys_mem_size.out] 1

%PFE-5: fpc8 user.notice logrotate: ALERT exited abnormally with [1]

No traffic loss or service degradation observed.

• These logs are informational and not service-impacting.
• Possible causes include:
  • Temporary script failure
  • Corruption in parameter/status files used by logrotate

Recommended actions:

1. Acknowledge the logs as non-impacting.
2. Reboot the affected FPC if the logs are persistent:

request chassis fpc slot <slot-number> restart