Nov 16

Get the IP addresses of local Docker containers

Reading time: < 1 minute

We have docker running and the containers have their own private network, thanks to this command we’re going to get the private IP address of all of them:

$ sudo docker inspect $(docker ps -q ) \
--format='{{ printf "%-50s" .Name}} {{range .NetworkSettings.Networks}}{{.IPAddress}} {{end}}'
/zerotier
/ntp                                               10.3.10.8
/nodered                                           10.3.10.11
/n8n                                               10.3.10.4
/ssh                                               10.3.10.9
/code                                              10.3.10.7
/semaphore                                         10.3.10.6
/rproxy                                            10.3.10.2
/homer                                             10.3.2.10.10
/pihole                                            10.3.10.27
/pihole_googledns                                  10.3.10.24
/pihole_opendns                                    10.3.10.23

Aug 25

socat: publish a port only available in localhost

Reading time: 1 – 2 minutes

Assume that we have a service only available in localhost (127.0.0.1/8) and we want to expose this port temporarily. Of course, you can use iptables for redirecting the port. But take care, this is not a simple DNAT because packets will not be evaluated by PREROUTING (-t nat) rules.

Another option is using an old-powerful Swiss knife tool: socat (github).

# binds public port to any local interface
socat TCP-LISTEN:<public_port>,fork TCP:127.0.0.1:<internal_port>
# binds only to an IP address
SOCAT_SOCKADDR=<interface_IP> socat TCP-LISTEN:<public_port>,fork TCP:127.0.0.1:<internal_port>

# examples:

# binds to all interfaces:
socat TCP-LISTEN:1880,fork TCP:127.0.0.1:1880
# just for an IP address of one interface:
SOCAT_SOCKADDR=10.2.0.110 socat TCP-LISTEN:1880,fork TCP:127.0.0.1:1880

May 03

Truncate docker logs

Reading time: < 1 minute Sometimes when a container is running for a long time especially when docker logs command is called the logs dump is extra long and then a recurrent search on google for reminding how to truncate a file is mandatory for avoiding this repeating task this is the trick that it saves me from that uncomfortable long log dump.

truncate -s 0 $(docker inspect --format='{{.LogPath}}' CONTAINER_ID)

Oct 20

Windows 10: enable/disable Hyper-V from CLI

Reading time: < 1 minute Assuming we're running a Windows shell with administrator privileges, using next commands is possible to enable, or disable, Hyper-V. In my case this is needed because when Hyper-V is running Virtualbox only can run 32bit virtual machines. I require Microsoft VM manager Hyper-V because I also run Docker for Windows and it's a requirement.

#enable Hyper-V
dism.exe /Online /Enable-Feature:Microsoft-Hyper-V /All

#disable Hyper-V
dism.exe /Online /Disable-Feature:Microsoft-Hyper-V