在 chroot 中运行 bind 时，mysql dlz 驱动程序无法解析 mysql 服务器 (rds) 的主机名。在 VPC 中使用 amazon ami（基于 centos）。
Aug 25 10:22:27 paper named-sdb[6812]: Loading 'Mysql zone' using driver mysql
Aug 25 10:23:48 paper named-sdb[6812]: mysql driver failed to create database connection after 4 attempts
Aug 25 10:23:48 paper named-sdb[6812]: SDLZ driver failed to load.
Aug 25 10:23:48 paper named-sdb[6812]: DLZ driver failed to load.
Aug 25 10:23:48 paper named-sdb[6812]: loading configuration: failure
Aug 25 10:23:48 paper named-sdb[6812]: exiting (due to fatal error)
Installed Packages
bind.x86_64 32:9.8.2-0.30.rc1.38.amzn1 @amzn-updates
bind-chroot.x86_64 32:9.8.2-0.30.rc1.38.amzn1 @amzn-updates
bind-libs.x86_64 32:9.8.2-0.30.rc1.38.amzn1 @amzn-updates
bind-sdb.x86_64 32:9.8.2-0.30.rc1.38.amzn1 @amzn-updates
bind-utils.x86_64 32:9.8.2-0.30.rc1.38.amzn1 @amzn-updates
我可以看到它尝试连接到 localhost 而不是 amazon dns 服务器来解析主机名。请注意，这是一个 udp 连接：
# netstat -nputwc |grep named
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
udp 0 0 127.0.0.1:41551 127.0.0.1:53 ESTABLISHED 5531/named-sdb
我可以通过命令行直接解析并连接 mysql 服务器。如果我将 bind 配置为不使用 chroot，bind 可以正确启动。您可以看到 bind 与 rds 服务器成功建立了 tcp 连接。
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 10.33.1.20:41700 10.33.42.9:3306 ESTABLISHED 5381/named-sdb
tcp 0 0 10.33.1.20:41711 10.33.42.9:3306 ESTABLISHED 5381/named-sdb
/etc/resolv.conf 的内容
; generated by /sbin/dhclient-script
search us-west-2.compute.internal
nameserver 10.33.0.2
先前的研究表明，该问题是由于 chroot 能够执行解析。我已将 /etc/resolv.conf 符号链接到 chroot /var/named/chroot/etc/resolv.conf，并复制了建议的库以执行解析，但没有成功。
/var/named/chroot/dev
/var/named/chroot/etc
/var/named/chroot/lib64
/var/named/chroot/usr
/var/named/chroot/var
/var/named/chroot/dev/null
/var/named/chroot/dev/random
/var/named/chroot/dev/zero
/var/named/chroot/etc/localtime
/var/named/chroot/etc/named
/var/named/chroot/etc/pki
/var/named/chroot/etc/resolv.conf
/var/named/chroot/etc/pki/dnssec-keys
/var/named/chroot/lib64/ld-linux-x86-64.so.2
/var/named/chroot/lib64/libgcc_s.so.1
/var/named/chroot/lib64/libnsl-2.17.so
/var/named/chroot/lib64/libnsl.so.1
/var/named/chroot/lib64/libnss_compat-2.17.so
/var/named/chroot/lib64/libnss_compat.so.2
/var/named/chroot/lib64/libnss_db-2.17.so
/var/named/chroot/lib64/libnss_db.so.2
/var/named/chroot/lib64/libnss_dns-2.17.so
/var/named/chroot/lib64/libnss_dns.so.2
/var/named/chroot/lib64/libnss_files-2.17.so
/var/named/chroot/lib64/libnss_files.so.2
/var/named/chroot/lib64/libnss_hesiod-2.17.so
/var/named/chroot/lib64/libnss_hesiod.so.2
/var/named/chroot/lib64/libnss_nis-2.17.so
/var/named/chroot/lib64/libnss_nis.so.2
/var/named/chroot/lib64/libnss_nisplus-2.17.so
/var/named/chroot/lib64/libnss_nisplus.so.2
/var/named/chroot/lib64/libresolv-2.17.so
/var/named/chroot/lib64/libresolv.so.2
/var/named/chroot/usr/lib64
/var/named/chroot/usr/lib64/bind
/var/named/chroot/usr/lib64/libevent-1.4.so.2
/var/named/chroot/usr/lib64/libevent-1.4.so.2.1.3
/var/named/chroot/usr/lib64/libevent-2.0.so.5
/var/named/chroot/usr/lib64/libevent-2.0.so.5.1.6
/var/named/chroot/usr/lib64/libevent.so
/var/named/chroot/usr/lib64/libevent_core-1.4.so.2
/var/named/chroot/usr/lib64/libevent_core-1.4.so.2.1.3
/var/named/chroot/usr/lib64/libevent_core-2.0.so.5
/var/named/chroot/usr/lib64/libevent_core-2.0.so.5.1.6
/var/named/chroot/usr/lib64/libevent_core.so
/var/named/chroot/usr/lib64/libevent_extra-1.4.so.2
/var/named/chroot/usr/lib64/libevent_extra-1.4.so.2.1.3
/var/named/chroot/usr/lib64/libevent_extra-2.0.so.5
/var/named/chroot/usr/lib64/libevent_extra-2.0.so.5.1.6
/var/named/chroot/usr/lib64/libevent_extra.so
/var/named/chroot/usr/lib64/libevent_openssl-2.0.so.5
/var/named/chroot/usr/lib64/libevent_openssl-2.0.so.5.1.6
/var/named/chroot/usr/lib64/libevent_openssl.so
/var/named/chroot/usr/lib64/libevent_pthreads-2.0.so.5
/var/named/chroot/usr/lib64/libevent_pthreads-2.0.so.5.1.6
/var/named/chroot/usr/lib64/libevent_pthreads.so
/var/named/chroot/usr/lib64/libnsl.so
/var/named/chroot/usr/lib64/libnss3.so
/var/named/chroot/usr/lib64/libnss_compat.so
/var/named/chroot/usr/lib64/libnss_db.so
/var/named/chroot/usr/lib64/libnss_dns.so
/var/named/chroot/usr/lib64/libnss_files.so
/var/named/chroot/usr/lib64/libnss_hesiod.so
/var/named/chroot/usr/lib64/libnss_nis.so
/var/named/chroot/usr/lib64/libnss_nisplus.so
/var/named/chroot/usr/lib64/libnssckbi.so
/var/named/chroot/usr/lib64/libnssdbm3.chk
/var/named/chroot/usr/lib64/libnssdbm3.so
/var/named/chroot/usr/lib64/libnsspem.so
/var/named/chroot/usr/lib64/libnsssysinit.so
/var/named/chroot/usr/lib64/libnssutil3.so
/var/named/chroot/usr/lib64/libresolv.so
/var/named/chroot/usr/lib64/libssl.so.1.0.1k
/var/named/chroot/usr/lib64/libssl.so.10
/var/named/chroot/usr/lib64/libssl3.so
答案1
解决方案：
不能在 chroot 中使用符号链接。
添加到您的 rc.local，在启动时运行：$ cp /etc/resolv.conf /var/named/chroot/etc/resolv.conf
这确保 chrooted bind 可以使用 amazon 在云初始化期间分配的名称服务器。它在 chroot 内解析 dns 不会有问题。