Posts tagged "linux"
Linux Connection NAT Helper not Working
Some protocols need more than one TCP or UDP connection. For NAT to work the firewall needs to open additional ports to allow client server connection automatically. Examples are FTP (port 21 handshake, additional ports for data), PPTP (port 1723 for handshake, proto GRE 47 for payload) Since Linux kernel (~) 4.7 th...
Debian Curl/PHP/wget etc show an certificate error falsely
Problem: curl php wget and others show a cert error like the following since 6. Oct 2021, even though the cert has not expired: curl: (60) SSL certificate problem: certificate has expired More details here: https://curl.haxx.se/docs/sslcerts.html curl performs SSL certificate verification by default, using a "bundle...
Devuan / Debian Versions
Admins who prefer a Unix style operation system and don't like the centralized "one tool doing it all" approach of systemd, switch to Devuan. This mostly improves uptime over boot time. Admins of servers don't care about boot time and prefer uptime. This list keeps track of the related versions of Devuan and Debian....
DHCP Relay on Linux
DHCP relaying is used to forward DHCP requests to a DHCP server if the client and the server are not on the same network. One standard implementation of this is isc-dhcp-relay which is part of the isc-dhcp package. Problem: The dhcrelay is forwarding the dhcp request to the dhcp server and the dhcp server is respond...
LS Style After Devuan 3 or Debian 10 Update
After Devuan 3 update ls output showed characters, that are not really in the directory listing. The reason is that "ls" draws quotes around filenames with spaces. This is a bug from my point of view, ls should never change the actual filenames. If a filename has quotes or double quotes it's even weirder . "ls" adds...
Time Format after Devuan 3 and Debian 10 Update
After updating to Devuan 3 the date command shows 12hours am/pm but my days have 24 hours. The locale was always en_US.UTF8 to keep sane command and error output. Debian 10 thinks they had to fix the correct hour display to the complicated one. Therefor all sysadmins like me have to apply the following workaround, t...
ARP and Broadcast Packets Missing
Problem: A Linux box with Debian 9 (kernel 4.9) on a HP server with Intel i40e (X710) network cards, is not reachable from neighbor machines, because ARP does not work. Discussion: while testing with tcpdump ARP worked, but later ARP stopped working again. When tcpdump is used with "-p" (non promiscuous mode) you ca...
MITMProxy and IOS 13
Problem: if you want to debug a IOS app with MITMProxy, the iPhone needs to trust the MITMProxy CA. This is done by going to http://mitm.it/ and clicking on the apple symbol. Then you have to accept the "profile" in Settings "downloaded profiles". Then you have to trust this new CA cert in "Settings" "General" "Abou...
Linux Live-boot Fails after Debian/Devuan Update
Problem: after updating from Debian 8 to Devuan 2 the overlay live-boot failes with "no such device" Discussion: I use a bootable USB stick combined with live-boot. In this case the USB stick partition 3 is a normal ext4 file system used as read only "plainroot" filesystem. Live-boot overlays this with an ramfs. As ...
Greenlock(-express) Letsencrypt Fails with ECONNRESET
Problem: after upgrading vom greenlock-express v2.0 to v2.5 and switching from acme-v1 to acme-v2 every attempt to register a new TLS cert with Letsencrypt fails with "ECONNRESET" Discussion: the new version of greenlock tries to validate the .well-known/acme-challenge file before asking letsencrypt for the certific...