/silverlining/etchosts.py

 1"""Handle /etc/hosts
 2
 3This has methods to put a new host->ip setting in /etc/hosts, as well
 4as get a setting from that file.
 5
 6As /etc/hosts can only be edited by root, this ultimately calls out to
 7sudo to do the actual edit.
 8"""
 9
10import os
11from silversupport.shell import run
12
13__all__ = ['set_etc_hosts']
14
15def set_etc_hosts(config, hostnames, ip):
16    """Sets a line in /etc/hosts to assign the hostname to the ip
17
18    This may add or edit to the file, or do nothing if is already set.
19    It will call a subcommand with sudo if necessary to edit.
20    """
21    assert not isinstance(hostnames, basestring)
22    fp = open('/etc/hosts')
23    hostnames = set(hostnames)
24    try:
25        for line in fp.read().splitlines():
26            line = line.strip()
27            if not line.strip() or line.startswith('#'):
28                continue
29            parts = line.split()
30            line_ip = parts[0]
31            line_hosts = parts[1:]
32            if line_ip == ip:
33                for hostname in list(hostnames):
34                    if hostname in line_hosts:
35                        config.logger.info('Found working ip %s' % line)
36                        hostnames.remove(hostname)
37                        return
38            force_update = False
39            for hostname in hostnames:
40                if hostname in line_hosts:
41                    force_update = True
42                    break
43            if force_update:
44                break
45    finally:
46        fp.close()
47
48    cmd = ["sudo", "python",
49           os.path.join(os.path.dirname(__file__), 'update_etc_hosts.py'),
50           "/etc/hosts",
51           ip] + list(hostnames)
52    config.logger.notify('The hostname/ip is not setup in /etc/hosts')
53    resp = config.ask('Would you like me to set it up? ')
54    if resp:
55        config.logger.notify('Executing %s' % ' '.join(cmd))
56        run(cmd)