Hi i have problems resolving localhost in a docker container
[devcontainer]$ cat /etc/hosts
127.0.0.1 localhost
[devcontainer]$ curl localhost
curl: (6) Could not resolve host: localhostalso node has the same problem
[devcontainer]$ /home/plutus/.vscode-server/bin/e713fe9b05fc24facbec8f34fb1017133858842b/node
Welcome to Node.js v14.16.0.
Type ".help" for more information.
> dns.lookup('localhost', {hints: dns.ADDRCONFIG|dns.V4MAPPED}, console.log)
GetAddrInfoReqWrap { callback: [Function: log], family: 0, hostname: 'localhost', oncomplete: [Function: onlookup]
}
> Error: getaddrinfo ENOTFOUND localhost at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:67:26) at GetAddrInfoReqWrap.callbackTrampoline (internal/async_hooks.js:131:14) { errno: -3007, code: 'ENOTFOUND', syscall: 'getaddrinfo', hostname: 'localhost'
}any idea what the problem could be despite /etc/hosts? It definitly contains localhost.
And yes normal hosts are working:
[devcontainer]$ curl google.de
<HTML><HEAD><meta http-equiv="content-type" content="text/html;charset=utf-8">1 Answer
The standard hostname lookup functions on Linux use /etc/nsswitch.conf to determine where they should look for information. Make sure that file exists and is world-readable.
The nsswitch.conf file specifies which modules to use for each database. For example, there is a standard 'files' module that reads /etc/hosts (and /etc/passwd); there is a 'dns' module which makes DNS queries; and it's possible to install modules for LDAP, NIS, MySQL, etc.
Make sure nsswitch.conf contains a hosts: line, and that the line mentions the files module somewhere in it (modules are processed left-to-right).
For example, typically it will be configured sorta like this (modern distros might include more modules, but that's the basic minimum that everyone has):
passwd: files
hosts: files dns
...This configuration tells the "hosts" lookup functions to first use the 'files' module (which reads /etc/hosts), and then if it has no succesful results, then use the 'dns' module (which makes DNS queries according to /etc/resolv.conf).
Each module exists as a library in /lib (or /usr/lib). So if you want to use the files module, then make sure that your system actually has /lib/libnss_files.so.2 installed.
Note that if the nsswitch.conf file is missing or unreadable, Glibc uses this hardcoded default configuration:
passwd: files
hosts: dns [!UNAVAIL=return] files
...This means that DNS will be tried first, and if it provides any answer (even a "not found"), the query will immediately stop there – the "files" module (to read /etc/hosts) won't be called at all.
You can test the name service configuration using getent:
To query according to nsswitch.conf:
getent hosts localhostgetent passwd rootTo query a specific module (bypassing nsswitch.conf):
getent -s dns hosts example.comgetent -s files hosts localhost
