Problem: after unmounting a LuKS crypted device, “cryptsetup close” fails with “Deivce is still in use”, even though it is not mounted anymore. Discussion: you can check with lsblk that it’s not mounted anymore: But with “dmsetup info” you can see that is still in use: “cryptsetup –debug close” CRYPT also shows device still in […]
cryptsetup close CRYPT Fails With “Device CRYPT is still in use.” Read More »
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 block “newly
Blocked Webserver Behind Fortiguard Read More »
Problem: When installing any package with pip in a venv python environment you get this error: We got this error on a Linux Debian machine, that had the latest Debian Bookworm running, but was an older machine. Upgrading and reinstalling python3 python3-venv oder python3-openssl did not help. Even upgrading to Debian Trixie didn’t change anything.
Pip Python TLS/SSL issues? Read More »
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 was attempting to connect to allmest
IP Scan Between Microsoft Clients on Port :7680 ? Read More »
Problem: ssh rejects connecting to old servers with this error: Discussion: After upgrading your client operating system, the new installed openssh-client disabled some old ssh key type and key exchange mechanisms, but you can enable them with command line options or in ssh_config. Solution 1: Add a command line option: Solution 2: Add a line
Reactivate old SSH host key types Read More »
Problem: you find a key and a cert file on, and need 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. Version: tested with openssl 3.0.11 on devuan 5
How to Check If an RSA Cert Matches an RSA Key Read More »
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: These errors are repeated several times, and the RAID controller driver “hpsa” for the SmartArray Controller P212 gives up, causing /dev/sda vanish. Discussion: While not absolutely
DMAR Kernel Log Errors and RAID Controller Crash Read More »
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 removed it’s claim “don’t be
Icon Missing When Adding a Webpage to the Android Homepage Read More »
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: Discussion: Cisco enforces this call-home feature for newer software releases. There is not much you
Cisco “Smart” License Read More »
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 and below, only TLS1.2 and above are
Chrome Refuses to Connect to Old Devices Read More »