Recent posts
cryptsetup close CRYPT Fails With "Device CRYPT is still in use."
Problem: after unmounting a LuKS crypted device, "cryptsetup close" fails with "Deivce is still in use", even though it is not mounted anymore. ...
Blocked Webserver Behind Fortiguard
Problem: A newly setup web server with working https cert is not reachable by some people with a certificate error. Discussion: After checking the cert info, you can see that the cert issuer is not the real one but FortiNet. The user is behind a FortiGuard firewall with WebFilter. Paranoid FortiGuard sysadmins may b...
Pip Python TLS/SSL issues?
Problem: When installing any package with pip in a venv python environment you get this error: WARNING: pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available. We got this error on a Linux Debian machine, that had the latest Debian Bookworm running, but was an older ...
IP Scan Between Microsoft Clients on Port :7680 ?
TL;DR: If you experience poor network performance on your wireless notebook, Microsoft may be using your device as a download server without your consent. Problem : I noticed a high number of requests between Windows clients in different network zones on a customer's firewall. It appeared that allmost every client w...
Reactivate old SSH host key types
Problem: ssh rejects connecting to old servers with this error: # ssh SRV Unable to negotiate with SRV port 22: no matching host key type found. Their offer: ssh-rsa or Unable to negotiate with SRV port 22: no matching key exchange method found. Their offer: diffie-hellman-group-exchange-sha1,diffie-hellman-group14-...
How to Check If an RSA Cert Matches an RSA Key
Problem: you find a key and a cert file on your server, and want to check if the cert matches the key. Solution: Check the modulo (n=p*q) of both key and cert to see if they are equal. $ openssl rsa -modulus -noout -in yourrsa.key Modulus=C8BEE8B687CC... $ openssl x509 -modulus -noout -in yourrsa.crt Modulus=C8BEE8B...
DMAR Kernel Log Errors and RAID Controller Crash
Problem: After upgrading an old HP ProLiant DL320 G6 Server to Linux kernel 6.1 (Devuan 5, Debian12) the system crashes during reboot. You will see the following kernel output: DMAR: DRHD: handling fault status reg 2 DMAR: [DMA Read] Request device [00:1e.0] PASID ffffffff fault addr df63e000 [fault reas...
Icon Missing When Adding a Webpage to the Android Homepage
Problem: when adding a shortcut of a webpage to the Android home screen, Chrome used <link rel="icon" ...> to give this shortcut an icon. Lately Google Chrome broke this feature (intentionally probably). Chrome just shows a grey round circle with a single letter instead of the provided icon. Discussion: Google remov...
Cisco "Smart" License
Problem: after upgrading Cisco ISO XE from 15 to 16 on an ASR-1001-X router, the permanent license of this router changes to "evaluation license" and Cisco forces you to use the call-home "feature". You will find log entries like these: *Jan 23 21:53:13.922: %SMART_LIC-6-AGENT_ENABLED: Smart Agent for Licensing is e...
Chrome Refuses to Connect to Old Devices
Problem: Chrome shows an error message like "NET::ERR_SSL_OBSOLETE_VERSION" when connecting to an old device. This might be an old network device or printer or KVM switch oder DRAC/RemoteInside port of servers. Discussion: since Chrome ~98 Google decided that you are not allowed to connect devices that use TLS1.1 an...