https://blogs.damiendye.uk/en/tags/linux/ Recent content in Linux on Damien Dye's Blog Hugo en-GB Tue, 15 Sep 2026 09:30:00 +0100 https://blogs.damiendye.uk/en/certificates/webex-certificates-on-a-build-server/ Tue, 15 Sep 2026 09:30:00 +0100 https://blogs.damiendye.uk/en/certificates/webex-certificates-on-a-build-server/ Webex on Linux says "Offline - No internet connection" on a machine whose network is fine: the OpenSSL Cisco ship looks for its trust store inside their own build container. What breaks, the fixes that fail, the one that works, what the build process got wrong, and how a security appliance vendor ships a client that cannot check a certificate. https://blogs.damiendye.uk/en/networking/a-vpn-out-of-parts-and-what-egress-really-is/ Mon, 14 Sep 2026 15:00:00 +0100 https://blogs.damiendye.uk/en/networking/a-vpn-out-of-parts-and-what-egress-really-is/ A VPN is a virtual link plus a carrier, and Linux ships a program for each: pppd or a tap device, and netcat. Building it both ways — over TCP, UDP, TLS and DTLS, with zstd compression — shows what a VPN is made of, and what egress really is: once an attacker has root and outbound is open, the tunnel is already installed. https://blogs.damiendye.uk/en/networking/ping-the-diagnostic-tool-that-opens-a-whole-lot-more/ Tue, 01 Sep 2026 08:05:00 +0100 https://blogs.damiendye.uk/en/networking/ping-the-diagnostic-tool-that-opens-a-whole-lot-more/ Why ping — ICMP echo, not the rest of the protocol — is a liability: a channel every host must answer, so a network that 'only allows ping' has a full VPN out. The threat, who can open one, three tunnels (Hans, icmptunnel, a Python one with AES-128), and the rule that shuts it: nftables, pf, Cisco, Junos, MikroTik and Windows. https://blogs.damiendye.uk/en/networking/how-far-away-is-the-firewall/ Fri, 28 Aug 2026 09:00:00 +0100 https://blogs.damiendye.uk/en/networking/how-far-away-is-the-firewall/ A connection that times out tells you nothing about where it died. TTL does. Here is how to count the hops to whatever is eating your port, on Linux, macOS, the BSDs, Solaris and Redox, with a script that needs no root on Linux.