I was revising some things in my startup scripts. I have a sort of generalized startup script in all the boxes in my constellation, which is capable of doing 8 or 10 different things that various of the boxes need to do at startup. <\/p>\n\n\n\n
For example, the various gateway boxes need to open up (auto)ssh connections to my house with reverse tunnels so I can reach them. On some boxes I want them to open a vncserver so I can get a graphical environment up. On some others they may need to mount some filesystems, with smb or nfs. On some of them I want them to figure out where their router is, in case I want to open up their router in a browser. On some I need them to establish the keychain. <\/p>\n\n\n\n\n\n\n\n
I noted that some of the raspbian pis would fail sometimes because the startup would run before the network was fully up, and I had to “relearn” that raspbian has a setting in raspi-config to wait for the network. Hmmm. How do they do that? <\/p>\n\n\n\n
I dug around and I learned that if you ask raspbian to wait for the network what it actually does is to use dhcpcd5 -q -w. The w parameter says “Wait for an address to be assigned before forking to the background.” Cool. <\/p>\n\n\n\n
I only use dhcpcd5 on the raspbian boxes, on most of the other linux boxes I use dhclient, or the inbuilt client in NetworkManager or systemd-networkd. While dhclient doesn’t have a similar parameter that I can find, NetworkManager does have a command for this: nm-online. On a system which used systemd-networkd and did not have NetworkManager, this can also be done with the one-shot systemd-networkd-wait-online service, but I haven’t done that. <\/p>\n","protected":false},"excerpt":{"rendered":"
I was revising some things in my startup scripts. I have a sort of generalized startup script in all the boxes in my constellation, which is capable of doing 8 or 10 different things that various of the boxes need to do at startup. For example, the various gateway boxes need to open up (auto)ssh … Continue reading Waiting for networks<\/span>