Help: DNS Resolver and Root Shell
Hui Li
openlinuxsource at gmail.com
Wed Oct 23 14:40:29 UTC 2013
On Tue, 2013-10-22 at 22:41 +0200, Denys Vlasenko wrote:
> On Tue, Oct 22, 2013 at 5:43 PM, Hui Li <openlinuxsource at gmail.com> wrote:
> > Yes.
> > 127.0.0.1 localhost
> > And I will get following error by hostname:
> > root at localhost:~# hostname -f
> > hostname: localhost: Resolver internal error
>
> Hmm, I don't know what
> Run it under strace -s99, post the log.
I have attached ping and hostname outputs.
>
> > root at localhost:~# hostname
> > localhost
>
> At least this works :)
>
> >> > /etc/resolv.conf:
> >> > nameserver 8.8.8.8
> >>
> >> Is 8.8.8.8 a correct IP of your DNS server?
> > 8.8.8.8 is Google's DNS server. I can ping it successfully.
>
> What else isn't working for you apart from "hostname -f"?
root at localhost:~# ping www.google.com
ping: bad address 'www.google.com'
-------------- next part --------------
execve("/bin/hostname", ["hostname", "-f"], [/* 9 vars */]) = 0
brk(0) = 0x7bf000
uname({sys="Linux", node="localhost", ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f20000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib/tls/v6l/vfp/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/tls/v6l/vfp", 0xbe903538) = -1 ENOENT (No such file or directory)
open("/lib/tls/v6l/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/tls/v6l", 0xbe903538) = -1 ENOENT (No such file or directory)
open("/lib/tls/vfp/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/tls/vfp", 0xbe903538) = -1 ENOENT (No such file or directory)
open("/lib/tls/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/tls", 0xbe903538) = -1 ENOENT (No such file or directory)
open("/lib/v6l/vfp/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/v6l/vfp", 0xbe903538) = -1 ENOENT (No such file or directory)
open("/lib/v6l/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/v6l", 0xbe903538) = -1 ENOENT (No such file or directory)
open("/lib/vfp/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/vfp", 0xbe903538) = -1 ENOENT (No such file or directory)
open("/lib/libm.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\270;\0\0004\0\0\0\234\236\6\0\2\0\0\0054\0 \0\10\0(\0%\0\"\0\6\0\0\0004\0\0\0004\0\0\0004\0\0\0\0\1\0\0\0\1\0\0\5\0\0\0\4\0\0\0\3\0\0\0\230g\6\0\230g\6\0\230g\6"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0555, st_size=490243, ...}) = 0
mmap2(NULL, 458888, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6e8a000
mprotect(0xb6ef2000, 28672, PROT_NONE) = 0
mmap2(0xb6ef9000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x67000) = 0xb6ef9000
close(3) = 0
open("/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0,\201\1\0004\0\0\0T\335\22\0\2\0\0\0054\0 \0\n\0(\0+\0(\0\1\0\0p\\\16\22\0\\\16\22\0\\\16\22\0\10\24\0\0\10\24\0\0\4\0\0\0\4\0\0\0\6\0\0\0004\0\0\0004\0\0\0004\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0555, st_size=1544998, ...}) = 0
mmap2(NULL, 1254768, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6d57000
mprotect(0xb6e7d000, 28672, PROT_NONE) = 0
mmap2(0xb6e84000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x125000) = 0xb6e84000
mmap2(0xb6e87000, 9584, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb6e87000
close(3) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f1f000
set_tls(0xb6f1f4c0, 0xb6f1fb98, 0xb6f22050, 0xb6f1f4c0, 0xb6f22050) = 0
mprotect(0xb6e84000, 8192, PROT_READ) = 0
mprotect(0xb6ef9000, 4096, PROT_READ) = 0
mprotect(0xb6f21000, 4096, PROT_READ) = 0
getuid32() = 0
uname({sys="Linux", node="localhost", ...}) = 0
brk(0) = 0x7bf000
brk(0x7e0000) = 0x7e0000
getpid() = 77
open("/etc/resolv.conf", O_RDONLY|O_CLOEXEC) = 3
fcntl64(3, F_GETFD) = 0x1 (flags FD_CLOEXEC)
fstat64(3, {st_mode=S_IFREG|0664, st_size=19, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f1e000
read(3, "nameserver 8.8.8.8\n", 4096) = 19
read(3, "", 4096) = 0
close(3) = 0
munmap(0xb6f1e000, 4096) = 0
uname({sys="Linux", node="localhost", ...}) = 0
socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0) = 3
connect(3, {sa_family=AF_LOCAL, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3) = 0
socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0) = 3
connect(3, {sa_family=AF_LOCAL, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3) = 0
open("/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 3
fstat64(3, {st_mode=S_IFREG|0664, st_size=326, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f1e000
read(3, "passwd: files\nshadow: files\ngroup: files\n\nhosts: files dns\n\nbootparams: nisplus ["..., 4096) = 326
read(3, "", 4096) = 0
close(3) = 0
munmap(0xb6f1e000, 4096) = 0
open("/lib/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\220\31\0\0004\0\0\0<\263\0\0\2\0\0\0054\0 \0\10\0(\0\36\0\33\0\6\0\0\0004\0\0\0004\0\0\0004\0\0\0\0\1\0\0\0\1\0\0\5\0\0\0\4\0\0\0\3\0\0\0\34\235\0\0\34\235\0\0\34\235\0"..., 512) = 512
close(3) = 0
open("/usr/lib/tls/v6l/vfp/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/tls/v6l/vfp", 0xbe9033f8) = -1 ENOENT (No such file or directory)
open("/usr/lib/tls/v6l/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/tls/v6l", 0xbe9033f8) = -1 ENOENT (No such file or directory)
open("/usr/lib/tls/vfp/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/tls/vfp", 0xbe9033f8) = -1 ENOENT (No such file or directory)
open("/usr/lib/tls/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/tls", 0xbe9033f8) = -1 ENOENT (No such file or directory)
open("/usr/lib/v6l/vfp/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/v6l/vfp", 0xbe9033f8) = -1 ENOENT (No such file or directory)
open("/usr/lib/v6l/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/v6l", 0xbe9033f8) = -1 ENOENT (No such file or directory)
open("/usr/lib/vfp/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/vfp", 0xbe9033f8) = -1 ENOENT (No such file or directory)
open("/usr/lib/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib", 0xbe9033f8) = -1 ENOENT (No such file or directory)
open("/lib/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0,\v\0\0004\0\0\0\374A\0\0\2\0\0\0054\0 \0\10\0(\0\36\0\33\0\6\0\0\0004\0\0\0004\0\0\0004\0\0\0\0\1\0\0\0\1\0\0\5\0\0\0\4\0\0\0\3\0\0\0\10:\0\0\10:\0\0\10:\0"..., 512) = 512
close(3) = 0
write(2, "hostname: localhost: Resolver internal error\n", 45) = 45
exit_group(1) = ?
+++ exited with 1 +++
-------------- next part --------------
execve("/bin/ping", ["ping", "www.google.com"], [/* 9 vars */]) = 0
brk(0) = 0x433000
uname({sys="Linux", node="localhost", ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f48000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib/tls/v6l/vfp/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/tls/v6l/vfp", 0xbe9f0528) = -1 ENOENT (No such file or directory)
open("/lib/tls/v6l/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/tls/v6l", 0xbe9f0528) = -1 ENOENT (No such file or directory)
open("/lib/tls/vfp/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/tls/vfp", 0xbe9f0528) = -1 ENOENT (No such file or directory)
open("/lib/tls/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/tls", 0xbe9f0528) = -1 ENOENT (No such file or directory)
open("/lib/v6l/vfp/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/v6l/vfp", 0xbe9f0528) = -1 ENOENT (No such file or directory)
open("/lib/v6l/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/v6l", 0xbe9f0528) = -1 ENOENT (No such file or directory)
open("/lib/vfp/libm.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/lib/vfp", 0xbe9f0528) = -1 ENOENT (No such file or directory)
open("/lib/libm.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\270;\0\0004\0\0\0\234\236\6\0\2\0\0\0054\0 \0\10\0(\0%\0\"\0\6\0\0\0004\0\0\0004\0\0\0004\0\0\0\0\1\0\0\0\1\0\0\5\0\0\0\4\0\0\0\3\0\0\0\230g\6\0\230g\6\0\230g\6"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0555, st_size=490243, ...}) = 0
mmap2(NULL, 458888, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6eb2000
mprotect(0xb6f1a000, 28672, PROT_NONE) = 0
mmap2(0xb6f21000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x67000) = 0xb6f21000
close(3) = 0
open("/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0,\201\1\0004\0\0\0T\335\22\0\2\0\0\0054\0 \0\n\0(\0+\0(\0\1\0\0p\\\16\22\0\\\16\22\0\\\16\22\0\10\24\0\0\10\24\0\0\4\0\0\0\4\0\0\0\6\0\0\0004\0\0\0004\0\0\0004\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0555, st_size=1544998, ...}) = 0
mmap2(NULL, 1254768, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6d7f000
mprotect(0xb6ea5000, 28672, PROT_NONE) = 0
mmap2(0xb6eac000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x125000) = 0xb6eac000
mmap2(0xb6eaf000, 9584, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb6eaf000
close(3) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f47000
set_tls(0xb6f474c0, 0xb6f47b98, 0xb6f4a050, 0xb6f474c0, 0xb6f4a050) = 0
mprotect(0xb6eac000, 8192, PROT_READ) = 0
mprotect(0xb6f21000, 4096, PROT_READ) = 0
mprotect(0xb6f49000, 4096, PROT_READ) = 0
getuid32() = 0
getpid() = 85
socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0) = 3
connect(3, {sa_family=AF_LOCAL, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3) = 0
socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0) = 3
connect(3, {sa_family=AF_LOCAL, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3) = 0
brk(0) = 0x433000
brk(0x454000) = 0x454000
open("/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 3
fcntl64(3, F_GETFD) = 0x1 (flags FD_CLOEXEC)
fstat64(3, {st_mode=S_IFREG|0664, st_size=326, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f46000
read(3, "passwd: files\nshadow: files\ngroup: files\n\nhosts: files dns\n\nbootparams: nisplus ["..., 4096) = 326
read(3, "", 4096) = 0
close(3) = 0
munmap(0xb6f46000, 4096) = 0
open("/etc/host.conf", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/etc/resolv.conf", O_RDONLY|O_CLOEXEC) = 3
fstat64(3, {st_mode=S_IFREG|0664, st_size=19, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f46000
read(3, "nameserver 8.8.8.8\n", 4096) = 19
read(3, "", 4096) = 0
close(3) = 0
munmap(0xb6f46000, 4096) = 0
uname({sys="Linux", node="localhost", ...}) = 0
open("/lib/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\220\31\0\0004\0\0\0<\263\0\0\2\0\0\0054\0 \0\10\0(\0\36\0\33\0\6\0\0\0004\0\0\0004\0\0\0004\0\0\0\0\1\0\0\0\1\0\0\5\0\0\0\4\0\0\0\3\0\0\0\34\235\0\0\34\235\0\0\34\235\0"..., 512) = 512
close(3) = 0
open("/usr/lib/tls/v6l/vfp/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/tls/v6l/vfp", 0xbe9efd48) = -1 ENOENT (No such file or directory)
open("/usr/lib/tls/v6l/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/tls/v6l", 0xbe9efd48) = -1 ENOENT (No such file or directory)
open("/usr/lib/tls/vfp/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/tls/vfp", 0xbe9efd48) = -1 ENOENT (No such file or directory)
open("/usr/lib/tls/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/tls", 0xbe9efd48) = -1 ENOENT (No such file or directory)
open("/usr/lib/v6l/vfp/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/v6l/vfp", 0xbe9efd48) = -1 ENOENT (No such file or directory)
open("/usr/lib/v6l/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/v6l", 0xbe9efd48) = -1 ENOENT (No such file or directory)
open("/usr/lib/vfp/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/vfp", 0xbe9efd48) = -1 ENOENT (No such file or directory)
open("/usr/lib/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat64("/usr/lib", 0xbe9efd48) = -1 ENOENT (No such file or directory)
open("/lib/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0,\v\0\0004\0\0\0\374A\0\0\2\0\0\0054\0 \0\10\0(\0\36\0\33\0\6\0\0\0004\0\0\0004\0\0\0004\0\0\0\0\1\0\0\0\1\0\0\5\0\0\0\4\0\0\0\3\0\0\0\10:\0\0\10:\0\0\10:\0"..., 512) = 512
close(3) = 0
write(2, "ping: bad address 'www.google.com'\n", 35) = 35
exit_group(1) = ?
+++ exited with 1 +++
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