Within the link Klaus told you, you can find this hint:
Perhaps it isn't yet installed. Install it and try update-grub once more. There is no need to edit '/etc/grub.d/40_custom' manually.
...
Type: Posts; User: Werner P. Schulz
Within the link Klaus told you, you can find this hint:
Perhaps it isn't yet installed. Install it and try update-grub once more. There is no need to edit '/etc/grub.d/40_custom' manually.
...
Cisco ASA5525-FTD-K9 Security Appliance with FirePower Services
$1000.00
Fortinet Fortiwifi 60D FG-60D Security Appliance Firewall / VPN w/ AC Adapter
$999.97
Palo Alto PA-3020 12-Port Network Security Firewall Appliance TESTED
$49.99
Fortinet Fortigate FG-61E | Firewall Network Security Appliance
$49.99
OPNsense six-port Gigabit router/firewall on Lanner FW-7535 hardware
$69.00
Palo Alto PA-220 Next-Gen Firewall 520-000309-00J w/ Power adapter
$69.98
Fortinet Fortiwifi 60D FWF-60D Security Appliance Firewall Wifi VPN
$29.99
PFSense F80 Firewall | Atom C2358 CPU | 4 Gigabit Ports | 2GB RAM | Fresh Reload
$75.00
Fortinet FortiGate 60F | 10 Gbps Firewall Security Throughput (FG-60F)- Open Box
$339.99
SonicWall TZ370 Network Security Appliance Firewall (02-SSC-2825)-Open Box
$383.99