I asked this question over on SO and it got moved here. That said I no longer have the ability to edit the question as if I owned it, or even accept the correct answer, but this turned out to be the true reason why and how to solve it:
Found here User "rohandhruva" on there gives the right answer:
This happens if you change the
hostname during the install process.
To solve the problem, edit the file
/etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 <ADD_YOURS_HERE>
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 <ADD_YOURS_HERE>
Short answer: you can't. Ports below 1024 can be opened only by root. As per comment - well, you can, using CAP_NET_BIND_SERVICE, but that approach, applied to java bin will make any java program to be run with this setting, which is undesirable, if not a security risk.
The long answer: you can redirect connections on port 80 to some other port you can open as normal user.
Run as root:
# iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
As loopback devices (like localhost) do not use the prerouting rules, if you need to use localhost, etc., add this rule as well (thanks @Francesco):
# iptables -t nat -I OUTPUT -p tcp -d 127.0.0.1 --dport 80 -j REDIRECT --to-ports 8080
NOTE: The above solution is not well suited for multi-user systems, as any user can open port 8080 (or any other high port you decide to use), thus intercepting the traffic. (Credits to CesarB).
EDIT: as per comment question - to delete the above rule:
# iptables -t nat --line-numbers -n -L
This will output something like:
Chain PREROUTING (policy ACCEPT)
num target prot opt source destination
1 REDIRECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8080 redir ports 8088
2 REDIRECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 redir ports 8080
The rule you are interested in is nr. 2, so to delete it:
# iptables -t nat -D PREROUTING 2
Best Answer
I'd not recommend trying to keep a process running all the time to do this. There are more simple methods. Your machine should have cron running which is a periodic task scheduler. You can schedule a process to run periodically, as frequently as once per minute to check the contents of the file and do what needs to be done. You might add something like this to the crontab:
see
man 1 crontabandman 5 crontabandman 8 cronfor more information about cron.Even better is to use incron which allows you to specify a process to be run any time this file is changed. If you have incron installed you'd add something like this to the incrontab:
Saying that anytime /etc/cluster.cf is modified, run your script. see
man 5 incrontabandman 1 incrontab