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November 23, 2016 08:30
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Find number of addresses already attributed by docker engine
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| #!/bin/sh | |
| # part by part: | |
| # 1. "brctl showmacs docker0" show the MAC addresses attached to the docker0 bridge | |
| # 2. "$(($(brctl showmacs docker0|wc -l) - 1))" returns the number of the lines returned by the brctl command minus 1 (to exclude the header, for cleanup) | |
| # 3. "uniq" show only unique enteries | |
| # 4. "wc -l" count the number of lines in the result. Which is also the number of running containers with an IP address behind the docker0 bridge. | |
| # Next address given by the docker engine is: (@IP of docker0)+the found number+1 | |
| brctl showmacs docker0|tail -n $(($(brctl showmacs docker0|wc -l) - 1))|uniq|wc -l | |
| #Alternative through docker | |
| #1. the docker inspect command with its arguments returns allocated IP addresses | |
| #2. the second part count the addresses returned by forst part | |
| docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $(docker ps -q)|wc -l | |
| # PS. If a container is given multiple addresses, on the same subnet or different subnets... you have to adapt these commands (if necessary) |
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