Junos OS supports only 1 rescue configuration file on a device. This rescue configuration is a safeguard feature that allows network administrators to revert to a known good configuration in case of a configuration error or issue, ensuring network stability.
In Junos OS, each device supports only one rescue configuration file. The rescue configuration is a specific configuration that can be saved and later retrieved if needed. This is used as a fallback configuration that you know works and can be applied in case of an emergency or if the current configuration has issues.
Reference:
"You can create a rescue configuration file by using the request system configuration rescue save operational mode command. Each Junos OS device can have only one rescue configuration file."

Theshow chassis hardwarecommand in Junos OS displays detailed information about the hardware installed in the device, including the chassis itself. This command provides a list of all hardware components, their serial numbers, part numbers, and version information. When looking for the chassis serial number specifically, this command is the most direct and comprehensive way to retrieve that information, as it includes the serial number of the chassis among the details provided.

In Juniper firewall filter configurations, "discard" and "accept" are two valid terminating actions for a term within a filter. The "discard" action drops the packet, preventing it from reaching its intended destination, while the "accept" action allows the packet to pass through the filter, proceeding to its next hop or destination.
"Count" is a non-terminating action that increments a counter every time a packet matches the term but does not inherently determine the packet's fate. "Next term" directs the evaluation to proceed to the next term in the filter for further processing, also a non-terminating action.

In Junos, when multiple policies are applied to a routing protocol for route export, the routes are evaluated in the order in which the policies are listed. In the exhibit, the OSPF configuration has three export policies listed: policy1, policy2, and policy3. The static route 10.10.10.0/24 does not match any terms in policy1; therefore, it is not rejected by policy1 but is instead passed on to the next policy in the sequence, which is policy2.
If the static route matches a term in policy2 that permits the route, it will be exported into OSPF. If it does not match in policy2, it will then be evaluated by policy3. If there is no match in policy3 as well, and assuming there are no more policies listed, the route would then be subject to the default routing policy behavior, which typically rejects the route unless an explicit accept statement is present in the policies.