RT3070L_USB_WIFI网卡在GT2440开发板上的移植和使用（四）--dhcp移植

6、dhcp的移植和应用

6.1、源码准备

(1)源码下载：ftp://ftp.isc.org/isc/
(2)源码文件确认：dhcp-4.2.5-P1.tar.gz

6.2、编译dhcp（如果不想看一步步的解决过程，可以跳过1，直接看2）

(1)尝试编译

tar zxf dhcp-4.2.5-P1.tar.gz     //解压源码
cd dhcp-4.2.5-P1 && ls            //到目录里面看有没有什么配置文件，只有一个configure
./configure --host=arm-linux    //用万能配置试一下
/@#################出错，无法确定/dev/random
checking for /dev/random... configure: error: cannot check for file existence when cross compiling
#################@/

vi config.log                 //查看一下配置的日志，在最后会找到出错的地方。
/@#################
config.log:1132:configure:7689: checking for /dev/random
configure:7688:# check for /dev/random (declares HAVE_DEV_RANDOM)         在7688行的问题，那就看一下
configure:7689:{ echo "$as_me:$LINENO: checking for /dev/random" >&5
configure:7690:echo $ECHO_N "checking for /dev/random... $ECHO_C" >&6; }
configure:7698:if test -r "/dev/random"; then
configure.ac:535:# check for /dev/random (declares HAVE_DEV_RANDOM)
#################@/
vi configure +7688        //打开看一下：
/@#################
# check for /dev/random (declares HAVE_DEV_RANDOM)
{ echo "$as_me:$LINENO: checking for /dev/random" >&5
echo $ECHO_N "checking for /dev/random... $ECHO_C" >&6; }
if test "${ac_cv_file__dev_random+set}" = set; then
  echo $ECHO_N "(cached) $ECHO_C" >&6
else
  test "$cross_compiling" = yes &&  #我们指定了编译工具直接执行这条出错。我们怎么解决呢？直接将ac_cv_file__dev_random这个变量指定为yes
  { { echo "$as_me:$LINENO: error: cannot check for file existence when cross compiling" >&5
echo "$as_me: error: cannot check for file existence when cross compiling" >&2;}
   { (exit 1); exit 1; }; }
if test -r "/dev/random"; then
  ac_cv_file__dev_random=yes
else
  ac_cv_file__dev_random=no
fi
fi
#################@/
./configure --host=arm-linux ac_cv_file__dev_random=yes //重新用这条命令配置试试
/@#################
     ISC DHCP source configure results:
    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Package:
  Name:          DHCP
  Version:       4.2.5-P1

C Compiler:      arm-linux-gcc

Flags:
  DEFS:          -DHAVE_CONFIG_H
  CFLAGS:        -g -O2  -Wall -Werror -fno-strict-aliasing -I${top_srcdir}/bind/include

Features:
  debug:         no
  failover:      
  execute:       

Developer:
  ATF unittests : no

Now you can type make to build ISC DHCP
#################@/
make        //编译一下看看有没有错误
/@#################显然不是一帆风顺的
.......
ar cru libomapi.a protocol.o buffer.o alloc.o result.o connection.o errwarn.o listener.o dispatch.o generic.o support.o handle.o message.o convert.o hash.o auth.o inet_addr.o array.o trace.o toisc.o iscprint.o isclib.o 
arm-linux-ranlib libomapi.a
arm-linux-gcc -DHAVE_CONFIG_H -I. -I../includes     -g -O2  -Wall -Werror -fno-strict-aliasing -I../bind/include -MT test.o -MD -MP -MF .deps/test.Tpo -c -o test.o test.c
mv -f .deps/test.Tpo .deps/test.Po
arm-linux-gcc  -g -O2  -Wall -Werror -fno-strict-aliasing -I../bind/include   -o svtest test.o libomapi.a ../bind/lib/libdns.a ../bind/lib/libisc.a #最后一条编译语句是这个，也就是这里出的错
/usr/local/arm/4.3.2/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.2/../../../../arm-none-linux-gnueabi/bin/ld: ../bind/lib/libdns.a(client.o): Relocations in generic ELF (EM: 3)
/usr/local/arm/4.3.2/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.2/../../../../arm-none-linux-gnueabi/bin/ld: ../bind/lib/libdns.a(client.o): Relocations in generic ELF (EM: 3)
/usr/local/arm/4.3.2/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.2/../../../../arm-none-linux-gnueabi/bin/ld: ../bind/lib/libdns.a(client.o): Relocations in generic ELF (EM: 3)
/usr/local/arm/4.3.2/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.2/../../../../arm-none-linux-gnueabi/bin/ld: ../bind/lib/libdns.a(client.o): Relocations in generic ELF (EM: 3)
/usr/local/arm/4.3.2/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.2/../../../../arm-none-linux-gnueabi/bin/ld: ../bind/lib/libdns.a(client.o): Relocations in generic ELF (EM: 3)
/usr/local/arm/4.3.2/bin/../lib/gcc/arm-none-linux-gnueabi/4.3.2/../../../../arm-none-linux-gnueabi/bin/ld: ../bind/lib/libdns.a(client.o): Relocations in generic ELF (EM: 3)
../bind/lib/libdns.a: could not read symbols: File in wrong format #这里说这些库的格式是错误的，怎么会格式错误呢。
找到这个库的编译路径去看看吧。
collect2: ld returned 1 exit status
make[1]: *** [svtest] Error 1
make[1]: Leaving directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/omapip'
make: *** [all-recursive] Error 1
#################@/
find -name "libdns.a"
/@#################
./bind/bind-9.8.4-P2/lib/export/dns/libdns.a
./bind/lib/libdns.a
#################@/
cd bind/bind-9.8.4-P2/lib/export/dns/ && ls    //进里面看一下，有很多*.o文件。随便看一个
file acl.o             //看一下这个文件的信息
/@#################    发现是386的。我是给arm开发板用的。这就不正常了。下面来解决这个问题
acl.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped
#################@/
cd - && vi Makefile    //进入源码根目录查看Makefile，源码中肯定有进入bind目录执行的命令。我们搜索bind
/@#################
#
# We have a lot of files that we want shipped with the distribution.
#
......
SUBDIRS = bind includes tests common dst omapip client dhcpctl relay server //搜索 SUBDIRS
nobase_include_HEADERS = dhcpctl/dhcpctl.h
all: all-recursive
搜索得到：对于SUBDIRS这些子目录，一个一个的进到里面执行make。
        list='$(SUBDIRS)'; for subdir in $$list; do \
          echo "Making $$target in $$subdir"; \
#################@/
cd bind && vi Makefile    //进到bind目录看看Makefile做什么，找到all
/@#################
all:
# Extract the source from the tarball, if it hasn't been already.
#先解压源文件
        @if test -d ${bindsrcdir} ; then                    \
                echo ${bindsrcdir} already unpacked... ;    \
        else                                                \
                gunzip -c bind.tar.gz | tar xf - ;          \
        fi

        @if test -z "${GMAKE}"; then                        \
                echo "unable to find gmake" 1>&2 ;          \
                exit 1;                                     \
        fi

# Configure the export libraries 然后配置文件
# Currently disable the epoll and devpoll options as they don't interact
# well with the DHCP code.
# If the top-level Bind Makefile exists we skip the configuration step
# as we assume it's done and won't change.  Doing a make clean will
# reset things if necessary.
#我们的配置没有配置为交叉编译所以不正确，我们试试修改加上交叉编译工具
        @if test -f ${bindsrcdir}/Makefile ; then                  \
                echo Bind export libraries already configured ;    \
        else                                                       \
                echo Configuring BIND Export libraries for DHCP. ; \
                rm -rf ./lib ./include ./configure.log ./build.log ./install.log ; \
--(cd ${bindsrcdir} && ./configure --disable-kqueue --disable-epoll --disable-devpoll --without-openssl --without-libxml2 --enable-exportlib --enable-threads=no --with-export-includedir=${binddir}/include --with-export-libdir=${binddir}/lib --with-gssapi=no > ${binddir}/configure.log); \
++                (cd ${bindsrcdir} && ./configure --host=arm-linux --disable-kqueue --disable-epoll --disable-devpoll --without-openssl --without-libxml2 --enable-exportlib --enable-threads=no --with-export-includedir=${binddir}/include --with-export-libdir=${binddir}/lib --with-gssapi=no > ${binddir}/configure.log); \
        fi

# Build and install the export libraries 配置和安装
# No need to do anything if we already have something installed.
        @if test -d ${binddir}/lib ; then                                    \
                echo Bind export libraries already installed ;               \
        else                                                                 \
                echo Building BIND Export libraries - this takes some time. ;\
                (cd ${bindsrcdir}/lib/export ;                               \
                  echo building in `pwd` ;                                   \
                  MAKE=${GMAKE} ${GMAKE} > ${binddir}/build.log) ;           \
                                                                             \
                echo Installing BIND Export libraries to ${binddir}. ;       \
                (cd ${bindsrcdir}/lib/export ;                               \
                  MAKE=${GMAKE} ${GMAKE} install > ${binddir}/install.log) ; \
        fi

#################@/修改后吧加压出的目录删掉，重新make看看还有什么错误
rm bind-9.8.4-P2/ -rf && make
/@#################还有错误啊。
Configuring BIND Export libraries for DHCP.
configure: error: cannot check for file existence when cross compiling
make: *** [all] Error 1 #configure的时候无法确认某些文件是否错误。
#################@/那就看看bind目录里的config.log吧
vi bind-9.8.4-P2/config.log
/@#################跳到最后，往前翻找到那个错误。
configure:22147: result: /dev/random
configure:22150: checking for /dev/random    //configure的22150行，还是这个文件找不到啊
configure:22156: error: cannot check for file existence when cross compiling
#################@/
vi bind-9.8.4-P2/configure +22150    //看看这行怎么说
/@#################
22137 case "$use_randomdev" in
22138         unspec)
22139                 case "$host" in
22140                         *-openbsd*)
22141                                 devrandom=/dev/arandom
22142                                 ;;
22143                         *)
22144                                 devrandom=/dev/random
22145                                 ;;
22146                 esac
22147                 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $devrandom" >&5
22148 $as_echo "$devrandom" >&6; }
22149                 as_ac_File=`$as_echo "ac_cv_file_$devrandom" | $as_tr_sh`
22150 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $devrandom" >&5
22151 $as_echo_n "checking for $devrandom... " >&6; }
22152 if eval \${$as_ac_File+:} false; then :
22153   $as_echo_n "(cached) " >&6
22154 else
22155   test "$cross_compiling" = yes && #还是指定了交叉编译就抛出错误。直接用根目录的配置试一试。
22156   as_fn_error $? "cannot check for file existence when cross compiling" "$LINENO" 5
22157 if test -r "$devrandom"; then
22158   eval "$as_ac_File=yes"
22159 else
22160   eval "$as_ac_File=no"
22161 fi
22162 fi
#################@/在bind目录的configure项再加个选项：
vi Makefile
/@#################
--                (cd ${bindsrcdir} && ./configure --host=arm-linux --disable-kqueue --disable-epoll --disable-devpoll --without-openssl --without-libxml2 --enable-exportlib --enable-threads=no --with-export-includedir=${binddir}/include --with-export-libdir=${binddir}/lib --with-gssapi=no > ${binddir}/configure.log); \
++                  (cd ${bindsrcdir} && ./configure ac_cv_file__dev_random=yes --host=arm-linux --disable-kqueue --disable-epoll --disable-devpoll --without-openssl --without-libxml2 --enable-exportlib --enable-threads=no --with-export-includedir=${binddir}/include --with-export-libdir=${binddir}/lib --with-gssapi=no > ${binddir}/configure.log); \
#################@/
rm -rf bind-9.8.4-P2/ && make //删除这个目录，重新make再看。
/@#################
Configuring BIND Export libraries for DHCP.
configure: error: BUILD_CC not set
make: *** [all] Error 1
#################@/BUILD_CC没有设置。我的思路：可以设置，或者退到上层目录make。也许是上层导入的。我们退到上层make
cd .. && make
/@#################还是没有设置啊。看来只能在里面指定试试了
root@book-desktop:/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1# make
Making all in bind
make[1]: Entering directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/bind'
bind-9.8.4-P2 already unpacked...
Configuring BIND Export libraries for DHCP.
configure: error: BUILD_CC not set
make[1]: *** [all] Error 1
make[1]: Leaving directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/bind'
make: *** [all-recursive] Error 1
#################@/
vi bind/Makefile    
/@#################改为这个。BUILD_CC是我们本机的编译器。
                (cd ${bindsrcdir} && ./configure ac_cv_file__dev_random=yes BUILD_CC=gcc --host=arm-linux --disable-kqueue --disable-epoll --disable-devpoll --without-openssl --without-libxml2 --enable-exportlib --enable-threads=no --with-export-includedir=${binddir}/include --with-export-libdir=${binddir}/lib --with-gssapi=no > ${binddir}/configure.log);
#################@/
cd bind && make  
/@#################又出错了
/bin/bash: ./gen: cannot execute binary file
make[2]: *** [include/dns/enumtype.h] Error 126
make[1]: *** [subdirs] Error 1
Installing BIND Export libraries to /work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/bind.
/bin/bash: ./gen: cannot execute binary file        //gen 无法执行的二进制文件
make[2]: *** [include/dns/enumclass.h] Error 126
make[1]: *** [subdirs] Error 1
make: *** [all] Error 2
#################@/搜索一下这个程序吧。
find -name "gen"                    //搜索一下这个程序在哪里
cd bind-9.8.4-P2/lib/export/dns         //进入搜索的目录
file gen                            //查看一下这个程序的内容
/@#################
gen: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.14, not stripped //这是一个arm平台的程序，当然不能在我的主机上执行了
#################@/那我们得修改他的Makefile了。里面有Makefile.in，Makefile是根据Makefile.in编译来的
bind/bind-9.8.4-P2/lib/export/dns# vi Makefile.in
/@#################改为PC机的工具链
168 gen: ${srcdir}/gen.c
--169         ${CC} ${ALL_CFLAGS} ${LDFLAGS} -o $@ ${srcdir}/gen.c ${LIBS}
++169         ${BUILD_CC} ${ALL_CFLAGS} ${LDFLAGS} -o $@ ${srcdir}/gen.c ${LIBS}
#################@/到这里基本上所有的问题就处理完了。
(2)编译总结：正确的步骤：把所有的都删除掉，重新开始：
tar xzf dhcp-4.2.5-P1.tar.gz        //解压源码
cd dhcp-4.2.5-P1                    //进入源码目录
./configure --host=arm-linux ac_cv_file__dev_random=yes //配置源码
cd bind                                //进入bind目录，修改里面的Makefile，加上这些:
./configure BUILD_CC=gcc ac_cv_file__dev_random=yes --host=arm-linux --disable-kqueue
tar xzf bind.tar.gz                    //解压里面的bind
cd bind-9.8.4-P2                    //进入解压的目录
修改 lib/export/dns/Makefile.in     //修改里面的Makefile.in
gen: ${srcdir}/gen.c
        ${CC} ${ALL_CFLAGS} ${LDFLAGS} -o $@ ${srcdir}/gen.c ${LIBS}
改为
gen: ${srcdir}/gen.c
        ${BUILD_CC} ${ALL_CFLAGS} ${LDFLAGS} -o $@ ${srcdir}/gen.c ${LIBS}

cd ../..
make        //编译吧，编译好了，如何安装呢？，打开Makefile，搜索一下install
/@#################
arm-linux-gcc  -g -O2  -Wall -Werror -fno-strict-aliasing -I../bind/include   -o dhcpd dhcpd-dhcpd.o dhcpd-dhcp.o dhcpd-bootp.o dhcpd-confpars.o dhcpd-db.o dhcpd-class.o dhcpd-failover.o dhcpd-omapi.o dhcpd-mdb.o dhcpd-stables.o dhcpd-salloc.o dhcpd-ddns.o dhcpd-dhcpleasequery.o dhcpd-dhcpv6.o dhcpd-mdb6.o dhcpd-ldap.o dhcpd-ldap_casa.o ../common/libdhcp.a ../omapip/libomapi.a ../dhcpctl/libdhcpctl.a ../bind/lib/libdns.a ../bind/lib/libisc.a 
make[2]: Leaving directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/server'
Making all in tests
make[2]: Entering directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/server/tests'
Making all in .
make[3]: Entering directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/server/tests'
make[3]: Nothing to be done for `all-am'.
make[3]: Leaving directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/server/tests'
make[2]: Leaving directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/server/tests'
make[1]: Leaving directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1/server'
make[1]: Entering directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1'
make[1]: Nothing to be done for `all-am'.
make[1]: Leaving directory `/work/gt2440_prj/zyp_RT3070/04_dhcp/dhcp-4.2.5-P1'
#################@/
vi Makefile //搜索install
/@#################可以看出DESTDIR是目的目录。
install-nobase_includeHEADERS: $(nobase_include_HEADERS)
        @$(NORMAL_INSTALL)
        test -z "$(includedir)" || $(MKDIR_P) "$(DESTDIR)$(includedir)"
        @$(am__vpath_adj_setup) \
        list='$(nobase_include_HEADERS)'; for p in $$list; do \
          if test -f "$$p"; then d=; else d="$(srcdir)/"; fi; \
          $(am__vpath_adj) \
          echo " $(nobase_includeHEADERS_INSTALL) '$$d$$p' '$(DESTDIR)$(includedir)/$$f'"; \
          $(nobase_includeHEADERS_INSTALL) "$$d$$p" "$(DESTDIR)$(includedir)/$$f"; \
        done
#################@/
make DESTDIR=$PWD/tmp install    //安装到$PWD/tmp

6.3、部署源码

cd tmp/usr/local/ && ls        //进入目录看一下
/@#################
bin  etc  include  lib  sbin  share
#################@/bin和sbin是应用程序。etc里面是配置文件。我们就需要这些就可以了。
把文件复制到你的开发板目录。
我将这些文件都复制到了网络文件系统/work/nfs_root/first_fs/gt2440_dev/dhcp
开发板端部署：
mount -t nfs -o nolock 192.168.15.15:/work/nfs_root/first_fs /mnt  //挂接网络文件系统
cd /usr/bin/
cp /mnt/gt2440_dev/dhcp/bin/* ./
cd ../sbin/
cp /mnt/gt2440_dev/dhcp/sbin/* ./
cd /etc/
cp /mnt/gt2440_dev/dhcp/etc/* ./
mv dhclient.conf.example dhclient.conf         
mv dhcpd.conf.example dhcpd.conf
这里部署完成了。
6.4、dhcp应用程序的使用
cd /myprj/rt3070l_usbwifi_driver/ 
insmod rt3070sta.ko                  //在rt3070l_usbwifi_driver目录下加载驱动
ifconfig ra0 up                           //打开无线设备
wpa_supplicant -B -c/etc/wpaconf/aes_tkip.conf -ira0 //开启wpa_supplicant这个服务
wpa_cli -ira0 status                   //wpa_cli这个命令连接到wpa服务器查看网卡状态
dhclient ra0                               //启动一下，
ifconfig                                      //查看一下：
/@#################没有成功啊。
ra0       Link encap:Ethernet  HWaddr 48:5D:60:90:5D:1A  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:997141 (973.7 KiB)  TX bytes:5310 (5.1 KiB)
#################@/
dhclient -d ra0                        //执行程序并打印调试信息
/@#################
Internet Systems Consortium DHCP Client 4.2.5-P1
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All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

can't create /var/db/dhclient.leases: No such file or directory //没有这个文件
execve (/etc/dhclient-script, ...): No such file or directory    //没有这个脚本，我们查看dhclient.conf这个配置文件\
发现需要运行这个脚本
Listening on LPF/ra0/48:5d:60:90:5d:1a
Sending on   LPF/ra0/48:5d:60:90:5d:1a
Sending on   Socket/fallback
Trying medium "-link0 -link1 -link2" 1
execve (/etc/dhclient-script, ...): No such file or directory
DHCPDISCOVER on ra0 to 255.255.255.255 port 67 interval 2
parse_option_buffer: malformed option vendor.<unknown> (code 33966151): option length exceeds option buffer length.
DHCPOFFER from 192.168.1.1
DHCPREQUEST on ra0 to 255.255.255.255 port 67
parse_option_buffer: malformed option vendor.<unknown> (code 33966151): option length exceeds option buffer length.
DHCPACK from 192.168.1.1
#################@/看看源码目录有没有这个脚本吧。发现是有的哦
cp client/scripts/linux /work/nfs_root/first_fs/gt2440_dev/dhcp/dhclient-script //复制大网络文件系统
cp /mnt/gt2440_dev/dhcp/dhclient-script /etc/        //开发板端执行。复制到/etc下
chmod a+x dhclient-script                            //加上执行权限，发现还是不会成功。需要修改脚本的内容
vi dhclient-script
/@#################
--#!/bin/bash
++#!/bin/sh
#################@/
dhclient -d ra0                        //执行程序并打印调试信息
/@#################
.......
can't create /var/db/dhclient.leases: No such file or directory //还会提示这个，一会儿创建一个空的好了。
....
bound to 192.168.1.2 -- renewal in 1508 seconds.
^C
#################@/
[root@GTStudio /etc]# ifconfig
/@#################
ra0       Link encap:Ethernet  HWaddr 48:5D:60:90:5D:1A  
          inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0 ^_^已经帮我们配置ip了
...
          RX bytes:4066020 (3.8 MiB)  TX bytes:11458 (11.1 KiB)
#################@/
[root@GTStudio /etc]# route
/@#################路由也设置好了^_^
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     *               255.255.255.0   U     0      0        0 ra0
default         192.168.1.1     0.0.0.0         UG    0      0        0 ra0
#################@/
[root@GTStudio /etc]# cat /etc/resolv.conf 
/@################# DNS也设置了啊
search fugue.com. home.vix.com.
nameserver 127.0.0.1
nameserver 192.168.1.1
#################@/
[root@GTStudio /etc]# ping news.qq.com
/@#################也可以ping通外网了。^_^^_^
PING news.qq.com (111.30.144.71): 56 data bytes
64 bytes from 111.30.144.71: seq=0 ttl=53 time=16.059 ms
64 bytes from 111.30.144.71: seq=1 ttl=53 time=266.647 ms
^C
--- news.qq.com ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 16.059/141.353/266.647 ms
#################@/
mkdir -p /var/db/                     //创建那个报错的目录
dhclient -d ra0                        //执行程序并打印调试信息就不会有错了。

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                                                                                                                                                                 2020.4.6