hosts編集後にnslookupで名前解決を行ってみたが反映されて無かったので疑問に思って調べた。
理由は簡単でnslookupではどうやらhostsを参照せずにDNSヘ直接問い合わせするためらしい。
トレースをみてみる。確かにhostsへの参照話でdnsへアクセスしていることがわかった。
$ strace -e trace=open nslookup hoge.com
open("/etc/ld.so.cache", O_RDONLY) = 3
open("/usr/lib64/liblwres.so.80", O_RDONLY) = 3
open("/usr/lib64/libdns.so.81", O_RDONLY) = 3
open("/usr/lib64/libbind9.so.80", O_RDONLY) = 3
open("/usr/lib64/libisccfg.so.82", O_RDONLY) = 3
open("/usr/nhnkrb5/lib/libgssapi_krb5.so.2", O_RDONLY) = 3
open("/usr/lib64/libcrypto.so.10", O_RDONLY) = 3
open("/usr/lib64/libisccc.so.80", O_RDONLY) = 3
open("/usr/lib64/libisc.so.83", O_RDONLY) = 3
open("/lib64/libdl.so.2", O_RDONLY) = 3
open("/lib64/libcap.so.2", O_RDONLY) = 3
open("/lib64/libpthread.so.0", O_RDONLY) = 3
open("/usr/lib64/libxml2.so.2", O_RDONLY) = 3
open("/lib64/libz.so.1", O_RDONLY) = 3
open("/lib64/libm.so.6", O_RDONLY) = 3
open("/lib64/libidn.so.11", O_RDONLY) = 3
open("/lib64/libc.so.6", O_RDONLY) = 3
open("/usr/nhnkrb5/lib/libkrb5.so.3", O_RDONLY) = 3
open("/usr/nhnkrb5/lib/libk5crypto.so.3", O_RDONLY) = 3
open("/lib64/libcom_err.so.2", O_RDONLY) = 3
open("/usr/nhnkrb5/lib/libkrb5support.so.0", O_RDONLY) = 3
open("/lib64/libresolv.so.2", O_RDONLY) = 3
open("/lib64/libattr.so.1", O_RDONLY) = 3
open("/lib64/libselinux.so.1", O_RDONLY) = 3
open("/proc/filesystems", O_RDONLY) = 3
open("/etc/pki/tls/legacy-settings", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.UTF-8/libdst.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libdst.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/libdst.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/libdst.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.UTF-8/libisc.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libisc.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/libisc.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/libisc.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/etc/pki/tls/openssl.cnf", O_RDONLY) = 6
open("/usr/share/locale/en_US.UTF-8/libdns.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libdns.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/libdns.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/libdns.cat", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/etc/resolv.conf", O_RDONLY) = 6
open("/usr/lib/locale/locale-archive", O_RDONLY) = 6
