This article explains why the " cat /var/db/scripts/op/aisfifo - file not present " message may be seen scrolling continuously during Routing Engine bootup on MX Series devices, and details what must be done to resolve the issue.

On MX devices that are running earlier Junos OS versions (prior to Junos OS Release 15.1) and have the Juniper AIS package, users may see that the Routing Engine is taking a long time to boot up after a reboot. Further, the following message is continuously seen on the screen: 

cat /var/db/scripts/op/aisfifo - file not present

Additionally, after the RE comes online, you might see high kernel utilization (around 60 percent) as shown in the show chassis routing-engine output.

Example (RE0 was rebooted in this case)

show chassis routing-engine 
Routing Engine status:
  Slot 0:
    Current state                  Backup
    Election priority              Master
    Temperature                 29 degrees C / 84 degrees F
    CPU temperature             25 degrees C / 77 degrees F
    DRAM                      16349 MB (16384 MB installed)
    Memory utilization          10 percent
    CPU utilization:
      User                      37 percent
      Background                 0 percent
      Kernel                    56 percent
      Interrupt                  6 percent
      Idle                       0 percent
    Model                          RE-S-1800x4
    Serial ID                      9009203386
    Start time                     2021-08-11 09:27:00 UTC
    Uptime                         23 minutes, 22 seconds
    Last reboot reason             0x1:power cycle/failure 
    Load averages:                 1 minute   5 minute  15 minute
                                       2.53       2.01       1.39
Routing Engine status:
  Slot 1:
    Current state                  Master
    Election priority              Backup
    Temperature                 27 degrees C / 80 degrees F
    CPU temperature             26 degrees C / 78 degrees F
    DRAM                      16349 MB (16384 MB installed)
    Memory utilization          15 percent
    CPU utilization:
      User                       6 percent
      Background                 0 percent
      Kernel                    20 percent
      Interrupt                 10 percent
      Idle                      63 percent
    Model                          RE-S-1800x4
    Serial ID                      9009137993
    Start time                     2020-12-23 08:12:09 UTC
    Uptime                         112 days, 1 hour, 38 minutes, 51 seconds
    Last reboot reason             0x1:power cycle/failure 
    Load averages:                 1 minute   5 minute  15 minute
                                       0.91       0.50       0.37

The following message is quite informative because it lists the package that RE0 is not able to find.

From RE1 shell

% ls -lt /var/db/scripts/op/ | egrep -i fifo
lrwxr-xr-x  1 root       wheel    37 Sep 25  2015 ais_fix_fifo.sh -> /packages/mnt/jais/op/ais_fix_fifo.sh
prwxrwx---  1 root       wheel     0 Sep 25  2015 aisfifo

From RE0 shell

% ls -lt /var/db/scripts/op/ | egrep -i fifo

As you can see, the aisfifo file is missing on RE0.

To resolve this problem, execute " commit script synchronize " on the current primary RE, which is RE1 in this case. After executing the command, the kernel utilization will come down for RE0, because it would now find the file that is looking for. See synchronize (Scripts) .

The other option is to delete the Juniper AIS package if it is not being used on the device by using request system software delete jais . Note that the command must be executed on both REs.