一 背景：
1 公司内部大量开发、测试、UAT环境机器都是CentOS 6.5的物理机/虚拟机；
2 公司在阿里云上的ECS机器环境同样多数为CentOS 6.5;
3 近期，公司内部在推Docker技术，而相对稳定且版本不至于太低的docker，需要部署在至少RHEL/CentOS 7.0以上版本的操作系统上。
二 说明：
本文档用于记录升级Centos 6.5到CentOS 7.2版本的操作步骤，以及升级后带来的问题和解决办法。升级前，本机的OS版本、内核版本、文件系统信息如下：
[root@dev-middleware ~]# cat /etc/redhat-release CentOS release 6.5 (Final) [root@dev-middleware ~]# uname -rm 2.6.32-431.el6.x86_64 x86_64 [root@dev-middleware ~]# df -Th Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/VolGroup-lv_root ext4 50G 40G 7.2G 85% / tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm /dev/sda1 ext4 485M 32M 428M 7% /boot /dev/mapper/VolGroup-lv_home ext4 144G 193M 136G 1% /home [root@dev-middleware ~]#
根据从网络上的获取的相关参考信息，本文档中的内容和步骤并不适用于Centos其它版本6.X升级至CentOS 7的参考。且，该升级是in-place-upgrade的升级方式，即直接在原机上执行升级的操作，存在一定风险。而官方推荐的非in-place-upgrade的方式，即先备份相关的文件和数据，然后安装CentOS 7系统，再恢复还原相关数据的作法，相对比较安全可控。
三 升级：
1 添加1个yum的repo文件：
vi /etc/yum.repo.d/upgrade.repo
内容为：
[upg] name=CentOS-$releasever - Upgrade Tool baseurl=http://dev.centos.org/centos/6/upg/x86_64/ gpgcheck=1 enabled=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
2 安装升级工具：
yum install redhat-upgrade-tool preupgrade-assistant-contents
3 执行预升级检查：
preupg -l preupg -s CentOS6_7
如果有类似下述错误：
I/O warning : failed to load external entity "/usr/share/openscap/xsl/security-guide.xsl" compilation error: file /usr/share/preupgrade/xsl/preup.xsl line 40 element import xsl:import : unable to load /usr/share/openscap/xsl/security-guide.xsl I/O warning : failed to load external entity "/usr/share/openscap/xsl/oval-report.xsl" compilation error: file /usr/share/preupgrade/xsl/preup.xsl line 41 element import xsl:import : unable to load /usr/share/openscap/xsl/oval-report.xsl I/O warning : failed to load external entity "/usr/share/openscap/xsl/sce-report.xsl" compilation error: file /usr/share/preupgrade/xsl/preup.xsl line 42 element import xsl:import : unable to load /usr/share/openscap/xsl/sce-report.xsl OpenSCAP Error:: Could not parse XSLT file '/usr/share/preupgrade/xsl/preup.xsl' [oscapxml.c:416] Unable to open file /root/preupgrade/result.html Usage: preupg [options] preupg: error: [Errno 2] No such file or directory: '/root/preupgrade/result.html'
则，原因是openscap软件包的版本太高。通过下述先删除，再安装的来办法解决：
yum erase openscap yum install http://dev.centos.org/centos/6/upg/x86_64/Packages/openscap-1.0.8-1.0.1.el6.centos.x86_64.rpm yum install redhat-upgrade-tool preupgrade-assistant-contents
4 再次执行，预升级检查：
preupg -s CentOS6_7
执行结果：
.... 094/096 ...done (NIS server maps check) 095/096 ...done (NIS server MAXUID and MAXGID limits check) 096/096 ...done (NIS server config file back-up) Assessment finished (time 02:15s) Result table with checks and their results for main contents: .... |Content for enabling and disabling services based on CentOS 6 system |needs_action | --------------------------------------------------------------------------------------------------------------- Tarball with results is stored here /root/preupgrade-results/preupg_results-170510111635.tar.gz . The latest assessment is stored in directory /root/preupgrade . Summary information: We found some potential in-place upgrade risks. Read the file /root/preupgrade/result.html for more details. Upload results to UI by command: e.g. preupg -u http://127.0.0.1:8099/submit/ -r /root/preupgrade-results/preupg_results-*.tar.gz .
执行升级的过程中，可能会有的一些不兼容问题，则都在上述的预升级检查结果中，需要关注并处理。
5 导入仓库的RPM签名证书
rpm --import http://172.16.11.36/yum/test/RPM-GPG-KEY-CentOS-7
需要说明的是，这里导入的是使用本地搭建的一个yum源的签名证书。这个本地源，是基于从网络上下载的CentOS-7-x86_64-DVD-1611.iso进行搭建的。当然，并不一定非要搭建本地yum源，也可以直接从下载的该ISO文件中，获取RPM-GPG-KEY-CentOS-7，直接在本地机器执行导入。为什么这么做，后面会有详细的解释和说明。
该文件的内容如下：
[root@localhost test]# cat RPM-GPG-KEY-CentOS-7 -----BEGIN PGP PUBLIC KEY BLOCK----- Version: GnuPG v1.4.5 (GNU/Linux) mQINBFOn/0sBEADLDyZ+DQHkcTHDQSE0a0B2iYAEXwpPvs67cJ4tmhe/iMOyVMh9 Yw/vBIF8scm6T/vPN5fopsKiW9UsAhGKg0epC6y5ed+NAUHTEa6pSOdo7CyFDwtn 4HF61Esyb4gzPT6QiSr0zvdTtgYBRZjAEPFVu3Dio0oZ5UQZ7fzdZfeixMQ8VMTQ 4y4x5vik9B+cqmGiq9AW71ixlDYVWasgR093fXiD9NLT4DTtK+KLGYNjJ8eMRqfZ Ws7g7C+9aEGHfsGZ/SxLOumx/GfiTloal0dnq8TC7XQ/JuNdB9qjoXzRF+faDUsj WuvNSQEqUXW1dzJjBvroEvgTdfCJfRpIgOrc256qvDMp1SxchMFltPlo5mbSMKu1 x1p4UkAzx543meMlRXOgx2/hnBm6H6L0FsSyDS6P224yF+30eeODD4Ju4BCyQ0jO IpUxmUnApo/m0eRelI6TRl7jK6aGqSYUNhFBuFxSPKgKYBpFhVzRM63Jsvib82rY 438q3sIOUdxZY6pvMOWRkdUVoz7WBExTdx5NtGX4kdW5QtcQHM+2kht6sBnJsvcB JYcYIwAUeA5vdRfwLKuZn6SgAUKdgeOtuf+cPR3/E68LZr784SlokiHLtQkfk98j NXm6fJjXwJvwiM2IiFyg8aUwEEDX5U+QOCA0wYrgUQ/h8iathvBJKSc9jQARAQAB tEJDZW50T1MtNyBLZXkgKENlbnRPUyA3IE9mZmljaWFsIFNpZ25pbmcgS2V5KSA8 c2VjdXJpdHlAY2VudG9zLm9yZz6JAjUEEwECAB8FAlOn/0sCGwMGCwkIBwMCBBUC CAMDFgIBAh4BAheAAAoJECTGqKf0qA61TN0P/2730Th8cM+d1pEON7n0F1YiyxqG QzwpC2Fhr2UIsXpi/lWTXIG6AlRvrajjFhw9HktYjlF4oMG032SnI0XPdmrN29lL F+ee1ANdyvtkw4mMu2yQweVxU7Ku4oATPBvWRv+6pCQPTOMe5xPG0ZPjPGNiJ0xw 4Ns+f5Q6Gqm927oHXpylUQEmuHKsCp3dK/kZaxJOXsmq6syY1gbrLj2Anq0iWWP4 Tq8WMktUrTcc+zQ2pFR7ovEihK0Rvhmk6/N4+4JwAGijfhejxwNX8T6PCuYs5Jiv hQvsI9FdIIlTP4XhFZ4N9ndnEwA4AH7tNBsmB3HEbLqUSmu2Rr8hGiT2Plc4Y9AO aliW1kOMsZFYrX39krfRk2n2NXvieQJ/lw318gSGR67uckkz2ZekbCEpj/0mnHWD 3R6V7m95R6UYqjcw++Q5CtZ2tzmxomZTf42IGIKBbSVmIS75WY+cBULUx3PcZYHD ZqAbB0Dl4MbdEH61kOI8EbN/TLl1i077r+9LXR1mOnlC3GLD03+XfY8eEBQf7137 YSMiW5r/5xwQk7xEcKlbZdmUJp3ZDTQBXT06vavvp3jlkqqH9QOE8ViZZ6aKQLqv pL+4bs52jzuGwTMT7gOR5MzD+vT0fVS7Xm8MjOxvZgbHsAgzyFGlI1ggUQmU7lu3 uPNL0eRx4S1G4Jn5 =OGYX -----END PGP PUBLIC KEY BLOCK----- [root@localhost test]#
6 执行升级：
centos-upgrade-tool-cli --network 7 --instrepo=http://vault.centos.org/centos/7.2.1511/os/x86_64/ setting up repos... .treeinfo | 1.1 kB 00:00 Preupgrade assistant risk check found risks for this upgrade. You can run preupg --riskcheck --verbose to view these risks. Addressing high risk issues is required before the in-place upgrade and ignoring these risks may result in a broken upgrade and unsupported upgrade. Please backup your data. ... ... (276/277): zlib-1.2.7-17.el7.x86_64.rpm | 90 kB 00:00 (277/277): zlib-devel-1.2.7-17.el7.x86_64.rpm | 50 kB 00:00 testing upgrade transaction rpm transaction 100% [======================================================================================================================================================] rpm install 100% [==========================================================================================================================================================] setting up system for upgrade Finished. Reboot to start upgrade.
7 根据提示，重启升级。
升级后的OS、内核版本、文件系统信息如下：
[root@dev-middleware conf.d]# cat /etc/redhat-release CentOS Linux release 7.2.1511 (Core) [root@dev-middleware conf.d]# uname -rm 3.10.0-327.el7.x86_64 x86_64 [root@dev-middleware conf.d]# df -Th 文件系统 类型 容量 已用 可用 已用% 挂载点 /dev/mapper/VolGroup-lv_root ext4 50G 43G 4.3G 91% / devtmpfs devtmpfs 1.9G 0 1.9G 0% /dev tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm tmpfs tmpfs 1.9G 80M 1.8G 5% /run tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup /dev/sda1 ext4 477M 110M 338M 25% /boot /dev/mapper/VolGroup-lv_home ext4 144G 354M 136G 1% /home [root@dev-middleware conf.d]#
四 遇到的问题，及解决办法
1 Downloading failed: invalid data in .treeinfo: No option ‘upgrade’ in section: ‘images-x86_64’
升级过程中，可能会遇到：No option ‘upgrade’ in section: ‘images-x86_64’：
redhat-upgrade-tool --network 7.0 --force --instrepo http://mirrors.aliyun.com/centos/7.3.1611/os/x86_64/ setting up repos... YumRepo Error: All mirror URLs are not using ftp, http[s] or file. Eg. Invalid release/ removing mirrorlist with no valid mirrors: /var/tmp/system-upgrade/base/mirrorlist.txt YumRepo Error: All mirror URLs are not using ftp, http[s] or file. Eg. Invalid release/ removing mirrorlist with no valid mirrors: /var/tmp/system-upgrade/extras/mirrorlist.txt YumRepo Error: All mirror URLs are not using ftp, http[s] or file. Eg. Invalid release/ removing mirrorlist with no valid mirrors: /var/tmp/system-upgrade/updates/mirrorlist.txt No upgrade available for the following repos: base extras updates .treeinfo | 946 B 00:00 getting boot images... Downloading failed: invalid data in .treeinfo: No option 'upgrade' in section: 'images-x86_64'
原因，如果使用互联上的签名文件的话，互联网上的yum源都会有相同的报错，.treeinfo: No option ‘upgrade’ in section: ‘images-x86_64’。即，网上的yum源下的文件.treeinfo里都没有upgrade选项。所以，经过测试，才使用了上述升级步骤中的导入本地rpm签名证书。
2 升级后，遇到nginx启动报错，Starting nginx: /usr/sbin/nginx: error while loading shared libraries: libpcre.so.0: cannot open shared object file: No such file or directory
[root@dev-middleware ~]# systemctl status nginx.service ● nginx.service - LSB: start and stop nginx Loaded: loaded (/etc/rc.d/init.d/nginx; bad; vendor preset: disabled) Active: failed (Result: exit-code) since 六 2017-05-27 16:49:28 CST; 5min ago Docs: man:systemd-sysv-generator(8) 5月 27 16:49:28 dev-middleware systemd[1]: Starting LSB: start and stop nginx... 5月 27 16:49:28 dev-middleware nginx[1661]: Starting nginx: /usr/sbin/nginx: error while loading shared libraries: libpcre.so.0: cannot open shared object file: No such file or directory 5月 27 16:49:28 dev-middleware nginx[1661]: [失败] 5月 27 16:49:28 dev-middleware systemd[1]: nginx.service: control process exited, code=exited status=1 5月 27 16:49:28 dev-middleware systemd[1]: Failed to start LSB: start and stop nginx. 5月 27 16:49:28 dev-middleware systemd[1]: Unit nginx.service entered failed state. 5月 27 16:49:28 dev-middleware systemd[1]: nginx.service failed. [root@dev-middleware ~]#
解决办法：
a 查找libpcre.so文件
[root@dev-middleware ~]# find / -name libpcre.so* /usr/lib64/libpcre.so.1.2.0 /usr/lib64/libpcre.so /usr/lib64/libpcre.so.1 /usr/lib64/libpcre.so.0 [root@dev-middleware ~]#
b 创建链接文件
[root@dev-middleware ~]# link /usr/lib64/libpcre.so.1 /lib64/libpcre.so.0
c 输出LD_LIBRARY_PATH环境变量
[root@dev-middleware ~]# export LD_LIBRARY_PATH=/usr/local/lib:/lib64:$LD_LIBRARY_PATH [root@dev-middleware ~]# echo $LD_LIBRARY_PATH /usr/local/lib:/lib64:/usr/lib64:/usr/local/lib: [root@dev-middleware ~]#
d 相关链接：
链接：
关于共享库找不到：
http://sempike.blogspot.com/2016/02/update-to-centos-7-libpcreso0-no-such.html
关于nginx启动报错：
http://blog.csdn.net/bzhxuexi/article/details/35821121
为防止以后出错，还是把export LD_LIBRARY_PATH=/usr/local/lib:/lib64:$LD_LIBRARY_PATH写入root的profile。
3 升级后，遇到类似问题：/ppas/9.3as/bin/edb-postgres: error while loading shared libraries: libsasl2.so.2: cannot open shared object file: No such file or directory
这是，之前一台运行CentOS 6.5的机器，上面跑着PostgreSQL数据库，升级到CentOS 7版本之后，数据库启动失败。
[enterprisedb@localhost ~]$ pg_ctl start /ppas/9.3as/bin/edb-postgres: error while loading shared libraries: libsasl2.so.2: cannot open shared object file: No such file or directory no data was returned by command ""/ppas/9.3as/bin/edb-postgres" -V" The program "edb-postgres" is needed by pg_ctl but was not found in the same directory as "/ppas/9.3as/bin/pg_ctl". Check your installation. [enterprisedb@localhost ~]$
解决办法：
a root创建链接文件：
[root@localhost ~]# find / -name libsasl2.* /usr/lib64/libsasl2.so.3.0.0 /usr/lib64/libsasl2.so.3 [root@localhost ~]# link /usr/lib64/libsasl2.so.3 /lib64/libsasl2.so.2
b 然后，PostgreSQL数据库用户，输出环境变量：
[enterprisedb@localhost ~]$ export LD_LIBRARY_PATH=/usr/lib64/:/lib64 [enterprisedb@localhost ~]$ echo $LD_LIBRARY_PATH /usr/lib64/:/lib64 [enterprisedb@localhost ~]$ pg_ctl status pg_ctl: no server running [enterprisedb@localhost ~]$ pg_ctl start server starting [enterprisedb@localhost ~]$ 2017-05-27 17:18:05 CST 日志: ** EnterpriseDB Dynamic Tuning Agent ******************************************** * System Utilization: 100% * * Database Version: 9.3.11.33 * * Operating System Version: * * Number of Processors: 0 * * Processor Type: * * Processor Architecture: * * Database Size: 0.1 GB * * RAM: 15.5 GB * * Shared Memory: 15839 MB * * Max DB Connections: 0 * * Autovacuum: on * * Autovacuum Naptime: 60 Seconds * * InfiniteCache: off * * InfiniteCache Servers: 0 * * InfiniteCache Size: 0.000 GB * ********************************************************************************* 2017-05-27 17:18:05 CST 日志: 已加载的库 "$libdir/dbms_pipe" 2017-05-27 17:18:05 CST 日志: 已加载的库 "$libdir/edb_gen" 2017-05-27 17:18:05 CST 日志: redirecting log output to logging collector process 2017-05-27 17:18:05 CST 提示: Future log output will appear in directory "pg_log". [enterprisedb@localhost ~]$