使用Nexus在centOS7上搭建maven私服时遇到问题

最近在尝试用Nexus在centOS7上搭建maven私服。
Nexus版本是2.12.0-01，centOS版本是7.3.1611。
在bin文件夹内输入./nexus start显示如下（已经在/etc/profile中设置RUN_AS_USER=root，因此下面的WARNING可以忽略）：

****************************************
WARNING - NOT RECOMMENDED TO RUN AS ROOT
****************************************
Starting Nexus OSS...
Started Nexus OSS.

看上去似乎正常启动。然而浏览器中输入http://localhost:8081/nexus无法打开。于是回去翻看启动日志wrapper.log，发现日志没到启动那一步就中止了。日志如下：

wrapper  | --> Wrapper Started as Daemon
wrapper  | Launching a JVM...
jvm 1    | Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=192m; support was removed in 8.0
jvm 1    | Wrapper (Version 3.2.3) http://wrapper.tanukisoftware.org
jvm 1    |   Copyright 1999-2006 Tanuki Software, Inc.  All Rights Reserved.
jvm 1    |
jvm 1    | 2017-04-07 08:21:07,241+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.jsw.JswLauncher - Starting with arguments: [./conf/jetty.xml, ./conf/jetty-requestlog.xml]
jvm 1    | 2017-04-07 08:21:07,244+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.jsw.JswLauncher - JVM ID: 1, JVM PID: 25802, Wrapper PID: 25800, User: root
jvm 1    | 2017-04-07 08:21:07,337+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder - Properties:
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   application-conf="/usr/local/nexus/nexusPak/nexus-2.12.0-01/../sonatype-work/nexus/conf"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   application-host="0.0.0.0"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   application-port="8080"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   bundleBasedir="/usr/local/nexus/nexusPak/nexus-2.12.0-01"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   java.awt.headless="true"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   networkaddress.cache.ttl="3600"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   nexus-app="/usr/local/nexus/nexusPak/nexus-2.12.0-01/nexus/WEB-INF"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   nexus-webapp="/usr/local/nexus/nexusPak/nexus-2.12.0-01/nexus"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   nexus-webapp-context-path="/nexus"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   nexus-work="/usr/local/nexus/nexusPak/sonatype-work/nexus"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   org.eclipse.ecf.provider.filetransfer.retrieve.readTimeout="30000"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   runtime="/usr/local/nexus/nexusPak/nexus-2.12.0-01/nexus/WEB-INF"
jvm 1    | 2017-04-07 08:21:07,338+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.ConfigurationBuilder -   security-xml-file="/usr/local/nexus/nexusPak/nexus-2.12.0-01/../sonatype-work/nexus/conf/security.xml"
jvm 1    | 2017-04-07 08:21:07,339+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.Launcher - Java: 1.8.0_121, Java HotSpot(TM) 64-Bit Server VM, Oracle Corporation, 25.121-b13
jvm 1    | 2017-04-07 08:21:07,339+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.Launcher - OS: Linux, 3.10.0-327.el7.x86_64, amd64
jvm 1    | 2017-04-07 08:21:07,339+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.Launcher - User: root, en, /root
jvm 1    | 2017-04-07 08:21:07,340+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.Launcher - CWD: /usr/local/nexus/nexusPak/nexus-2.12.0-01
jvm 1    | 2017-04-07 08:21:07,354+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.Launcher - TMP: /usr/local/nexus/nexusPak/nexus-2.12.0-01/tmp
jvm 1    | 2017-04-07 08:21:07,355+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.jetty.JettyServer - Starting
jvm 1    | 2017-04-07 08:21:07,362+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.jetty.JettyServer - Applying configuration: file:/usr/local/nexus/nexusPak/nexus-2.12.0-01/conf/jetty.xml
jvm 1    | 2017-04-07 08:21:07,569+0000 INFO  [WrapperListener_start_runner] *SYSTEM org.sonatype.nexus.bootstrap.jetty.JettyServer - Applying configuration: file:/usr/local/nexus/nexusPak/nexus-2.12.0-01/conf/jetty-requestlog.xml
jvm 1    | 2017-04-07 08:21:07,583+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.nexus.bootstrap.jetty.JettyServer - Starting: org.eclipse.jetty.server.Server@af7562c
jvm 1    | 2017-04-07 08:21:07,586+0000 INFO  [jetty-main-1] *SYSTEM org.eclipse.jetty.server.Server - jetty-8.1.16.v20140903
jvm 1    | 2017-04-07 08:21:08,235+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.nexus.webapp.WebappBootstrap - Initializing
jvm 1    | 2017-04-07 08:21:08,235+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.nexus.webapp.WebappBootstrap - Using bootstrap launcher configuration
jvm 1    | 2017-04-07 08:21:09,371+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.nexus.webapp.metrics.MetricsModule - Metrics support configured
jvm 1    | 2017-04-07 08:21:11,516+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.sisu.goodies.eventbus.internal.DefaultEventBus - Using Reentrant Guava EventBus
jvm 1    | 2017-04-07 08:21:11,557+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.security.configuration.source.FileSecurityConfigurationSource - Loading Security configuration from /usr/local/nexus/nexusPak/nexus-2.12.0-01/../sonatype-work/nexus/conf/security-configuration.xml
jvm 1    | 2017-04-07 08:21:11,916+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.sisu.ehcache.CacheManagerComponentImpl - Loading configuration from: file:/usr/local/nexus/nexusPak/nexus-2.12.0-01/nexus/WEB-INF/classes/ehcache.xml
jvm 1    | 2017-04-07 08:21:12,015+0000 INFO  [jetty-main-1] *SYSTEM com.thoughtworks.xstream.XStream - Version: 1.4.6-SONATYPE-03, white-list support available
jvm 1    | 2017-04-07 08:21:12,079+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.nexus.proxy.registry.DefaultRepositoryTypeRegistry - Registered default repository types.
jvm 1    | 2017-04-07 08:21:12,139+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.nexus.events.EventSubscriberHost - Initialized
jvm 1    | 2017-04-07 08:21:12,143+0000 INFO  [jetty-main-1] *SYSTEM org.sonatype.nexus.NxApplication -