centos7.0—Unit network.service could not be found_unit networkmanager.service could not be found.

环境：centos7.0

#systemctl status network
Unit network.service could not be found.

解决：#yum install systemd

过程：

服务器重启发现网络服务没了，查看之前的操作，因为yum install  lvm2报错

[root@vm~]# yum install lvm2
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Resolving Dependencies
--> Running transaction check
---> Package lvm2.x86_64 7:2.02.186-7.el7_8.1 will be installed
--> Processing Dependency: lvm2-libs = 7:2.02.186-7.el7_8.1 for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Processing Dependency: device-mapper-persistent-data >= 0.7.0-0.1.rc6 for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Processing Dependency: liblvm2app.so.2.2(Base)(64bit) for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Processing Dependency: libdevmapper-event.so.1.02(Base)(64bit) for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Processing Dependency: libaio.so.1(LIBAIO_0.4)(64bit) for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Processing Dependency: libaio.so.1(LIBAIO_0.1)(64bit) for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Processing Dependency: liblvm2app.so.2.2()(64bit) for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Processing Dependency: libdevmapper-event.so.1.02()(64bit) for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Processing Dependency: libaio.so.1()(64bit) for package: 7:lvm2-2.02.186-7.el7_8.1.x86_64
--> Running transaction check
---> Package device-mapper-event-libs.x86_64 7:1.02.164-7.el7_8.1 will be installed
---> Package device-mapper-persistent-data.x86_64 0:0.8.5-2.el7 will be installed
---> Package libaio.x86_64 0:0.3.109-13.el7 will be installed
---> Package lvm2-libs.x86_64 7:2.02.186-7.el7_8.1 will be installed
--> Processing Dependency: device-mapper-event = 7:1.02.164-7.el7_8.1 for package: 7:lvm2-libs-2.02.186-7.el7_8.1.x86_64
--> Running transaction check
---> Package device-mapper-event.x86_64 7:1.02.164-7.el7_8.1 will be installed
--> Processing Dependency: device-mapper = 7:1.02.164-7.el7_8.1 for package: 7:device-mapper-event-1.02.164-7.el7_8.1.x86_64
--> Running transaction check
---> Package device-mapper.x86_64 7:1.02.84-14.el7 will be updated
--> Processing Dependency: device-mapper = 7:1.02.84-14.el7 for package: 7:device-mapper-libs-1.02.84-14.el7.x86_64
---> Package device-mapper.x86_64 7:1.02.158-2.el7_7.2 will be updated
--> Processing Dependency: device-mapper = 7:1.02.158-2.el7_7.2 for package: 7:device-mapper-libs-1.02.158-2.el7_7.2.x86_64
---> Package device-mapper.x86_64 7:1.02.164-7.el7_8.1 will be an update
--> Running transaction check
---> Package device-mapper.x86_64 7:1.02.84-14.el7 will be updated
---> Package device-mapper-libs.x86_64 7:1.02.84-14.el7 will be updated
---> Package device-mapper-libs.x86_64 7:1.02.158-2.el7_7.2 will be updated
---> Package device-mapper-libs.x86_64 7:1.02.164-7.el7_8.1 will be an update
--> Finished Dependency Resolution
Error: Package: 7:device-mapper-libs-1.02.84-14.el7.x86_64 (@anaconda)
           Requires: device-mapper = 7:1.02.84-14.el7
           Removing: 7:device-mapper-1.02.84-14.el7.x86_64 (@anaconda)
               device-mapper = 7:1.02.84-14.el7
           Updated By: 7:device-mapper-1.02.164-7.el7_8.1.x86_64 (updates)
               device-mapper = 7:1.02.164-7.el7_8.1
           Removing: 7:device-mapper-1.02.158-2.el7_7.2.x86_64 (installed)
               device-mapper = 7:1.02.158-2.el7_7.2
           Updated By: 7:device-mapper-1.02.164-7.el7_8.1.x86_64 (updates)
               device-mapper = 7:1.02.164-7.el7_8.1
           Available: 7:device-mapper-1.02.164-7.el7.x86_64 (base)
               device-mapper = 7:1.02.164-7.el7
 You could try using --skip-broken to work around the problem
** Found 20 pre-existing rpmdb problem(s), 'yum check' output follows:
audit-libs-2.8.5-4.el7.x86_64 is a duplicate with audit-libs-2.3.3-4.el7.x86_64
centos-release-7-7.1908.0.el7.centos.x86_64 is a duplicate with centos-release-7-0.1406.el7.centos.2.3.x86_64
cryptsetup-libs-2.0.3-5.el7.x86_64 is a duplicate with cryptsetup-libs-1.6.3-2.el7.x86_64
7:device-mapper-1.02.158-2.el7_7.2.x86_64 is a duplicate with 7:device-mapper-1.02.84-14.el7.x86_64
7:device-mapper-libs-1.02.158-2.el7_7.2.x86_64 is a duplicate with 7:device-mapper-libs-1.02.84-14.el7.x86_64
dracut-033-564.el7.x86_64 is a duplicate with dracut-033-161.el7.x86_64
glib2-2.56.1-5.el7.x86_64 is a duplicate with glib2-2.36.3-5.el7.x86_64
kmod-20-25.el7.x86_64 is a duplicate with kmod-14-9.el7.x86_64
libselinux-2.5-14.1.el7.x86_64 has installed conflicts selinux-policy-base < ('0', '3.13.1', '66'): selinux-policy-targeted-3.12.1-153.el7.noarch
libselinux-2.5-14.1.el7.x86_64 has installed conflicts systemd < ('0', '219', '20'): systemd-208-11.el7.x86_64
libselinux-2.5-14.1.el7.x86_64 is a duplicate with libselinux-2.2.2-6.el7.x86_64
libselinux-python-2.5-14.1.el7.x86_64 is a duplicate with libselinux-python-2.2.2-6.el7.x86_64
libsemanage-2.5-14.el7.x86_64 has installed conflicts selinux-policy-base < ('0', '3.13.1', '66'): selinux-policy-targeted-3.12.1-153.el7.noarch
libsemanage-2.5-14.el7.x86_64 is a duplicate with libsemanage-2.1.10-16.el7.x86_64
libsepol-2.5-10.el7.x86_64 is a duplicate with libsepol-2.1.9-3.el7.x86_64
systemd-219-67.el7_7.2.x86_64 has installed conflicts dracut < ('0', '033', '243'): dracut-033-161.el7.x86_64
systemd-219-67.el7_7.2.x86_64 has installed conflicts initscripts < ('0', '9.49.28', '1'): initscripts-9.49.17-1.el7.x86_64
systemd-219-67.el7_7.2.x86_64 is a duplicate with systemd-208-11.el7.x86_64
systemd-libs-219-67.el7_7.2.x86_64 is a duplicate with systemd-libs-208-11.el7.x86_64
systemd-sysv-219-67.el7_7.2.x86_64 is a duplicate with systemd-sysv-208-11.el7.x86_64

-----------------------------------------------------------------------------------------------------------------------------------------

查看有问题的包
[root@vm ~]# rpm -qa |grep device-mapper
device-mapper-libs-1.02.158-2.el7_7.2.x86_64
device-mapper-1.02.84-14.el7.x86_64
device-mapper-1.02.158-2.el7_7.2.x86_64
device-mapper-libs-1.02.84-14.el7.x86_64

-------------------------------------------------------------------------------------------------------------------------------------------

删掉问题包的时候，也一起移除了 systemd 这个包
[root@vm ~]# yum remove device-mapper-libs-1.02.158-2.el7_7.2.x86_64
Loaded plugins: fastestmirror
Resolving Dependencies
--> Running transaction check
---> Package device-mapper-libs.x86_64 7:1.02.158-2.el7_7.2 will be erased
..................

=============================================================================================================================================
 Package                               Arch                      Version                                  Repository                    Size
=============================================================================================================================================
Removing:
 device-mapper-libs                    x86_64                    7:1.02.158-2.el7_7.2                     installed                    391 k
Removing for dependencies:
 cryptsetup-libs                       x86_64                    2.0.3-5.el7                              installed                    1.2 M
 device-mapper                         x86_64                    7:1.02.158-2.el7_7.2                     installed                    332 k
 dracut                                x86_64                    033-564.el7                              installed                    884 k
 systemd                               x86_64                    219-67.el7_7.2                           installed                     23 M
 systemd-sysv                          x86_64                    219-67.el7_7.2                           installed                    3.9 k

Transaction Summary
=============================================================================================================================================
Remove  1 Package (+5 Dependent packages)

Installed size: 26 M
Is this ok [y/N]: y

----------------------------------------------------------------------------------------------------------------

[root@vm ~]# yum install lvm2

....................................................

 发现Unit network.service could not be found问题，手工做本地yum源，重新yum install systemd。

[root@systemd]# yum install systemd
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Resolving Dependencies
--> Running transaction check
---> Package systemd.x86_64 0:208-11.el7 will be updated
--> Processing Dependency: systemd = 208-11.el7 for package: libgudev1-208-11.el7.x86_64
--> Processing Dependency: systemd = 208-11.el7 for package: systemd-sysv-208-11.el7.x86_64
---> Package systemd.x86_64 0:219-73.el7_8.5 will be an update
--> Processing Dependency: systemd-libs = 219-73.el7_8.5 for package: systemd-219-73.el7_8.5.x86_64
--> Processing Dependency: libcryptsetup.so.12(CRYPTSETUP_2.0)(64bit) for package: systemd-219-73.el7_8.5.x86_64
--> Processing Dependency: libcryptsetup.so.12()(64bit) for package: systemd-219-73.el7_8.5.x86_64
--> Running transaction check
---> Package cryptsetup-libs.x86_64 0:1.6.3-2.el7 will be updated
---> Package cryptsetup-libs.x86_64 0:2.0.3-6.el7 will be an update
---> Package libgudev1.x86_64 0:208-11.el7 will be updated
---> Package libgudev1.x86_64 0:219-73.el7_8.5 will be an update
---> Package systemd-libs.x86_64 0:208-11.el7 will be updated
---> Package systemd-libs.x86_64 0:219-67.el7_7.2 will be updated
---> Package systemd-libs.x86_64 0:219-73.el7_8.5 will be an update
---> Package systemd-sysv.x86_64 0:208-11.el7 will be updated
---> Package systemd-sysv.x86_64 0:219-73.el7_8.5 will be an update
--> Processing Conflict: systemd-219-73.el7_8.5.x86_64 conflicts initscripts < 9.49.28-1
--> Restarting Dependency Resolution with new changes.
--> Running transaction check
---> Package initscripts.x86_64 0:9.49.17-1.el7 will be updated
---> Package initscripts.x86_64 0:9.49.49-1.el7 will be an update
--> Processing Conflict: initscripts-9.49.49-1.el7.x86_64 conflicts redhat-release < 7.5-0.11
--> Restarting Dependency Resolution with new changes.
--> Running transaction check
---> Package centos-release.x86_64 0:7-0.1406.el7.centos.2.3 will be updated
---> Package centos-release.x86_64 0:7-7.1908.0.el7.centos will be updated
---> Package centos-release.x86_64 0:7-8.2003.0.el7.centos will be an update
--> Processing Conflict: systemd-219-73.el7_8.5.x86_64 conflicts dracut < 033-243
--> Restarting Dependency Resolution with new changes.
--> Running transaction check
---> Package dracut.x86_64 0:033-161.el7 will be updated
--> Processing Dependency: dracut = 033-161.el7 for package: dracut-config-rescue-033-161.el7.x86_64
--> Processing Dependency: dracut = 033-161.el7 for package: dracut-network-033-161.el7.x86_64
---> Package dracut.x86_64 0:033-568.el7 will be an update
--> Running transaction check
---> Package dracut-config-rescue.x86_64 0:033-161.el7 will be updated
---> Package dracut-config-rescue.x86_64 0:033-568.el7 will be an update
---> Package dracut-network.x86_64 0:033-161.el7 will be updated
---> Package dracut-network.x86_64 0:033-568.el7 will be an update
--> Finished Dependency Resolution

Dependencies Resolved

=============================================================================================================================================
 Package                                 Arch                      Version                                  Repository                  Size
=============================================================================================================================================
Updating:
 centos-release                          x86_64                    7-8.2003.0.el7.centos                    base                        26 k
 dracut                                  x86_64                    033-568.el7                              base                       329 k
 initscripts                             x86_64                    9.49.49-1.el7                            base                       440 k
 systemd                                 x86_64                    219-73.el7_8.5                           updates                    5.1 M
Updating for dependencies:
 cryptsetup-libs                         x86_64                    2.0.3-6.el7                              base                       339 k
 dracut-config-rescue                    x86_64                    033-568.el7                              base                        60 k
 dracut-network                          x86_64                    033-568.el7                              base                       103 k
 libgudev1                               x86_64                    219-73.el7_8.5                           updates                    106 k
 systemd-libs                            x86_64                    219-73.el7_8.5                           updates                    416 k
 systemd-sysv                            x86_64                    219-73.el7_8.5                           updates                     93 k

Transaction Summary
=============================================================================================================================================
Upgrade  4 Packages (+6 Dependent packages)

Total download size: 6.9 M
Is this ok [y/d/N]: y
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
(1/10): centos-release-7-8.2003.0.el7.centos.x86_64.rpm                                                               |  26 kB  00:00:00     
(2/10): cryptsetup-libs-2.0.3-6.el7.x86_64.rpm                                                                        | 339 kB  00:00:00     
(3/10): dracut-033-568.el7.x86_64.rpm                                                                                 | 329 kB  00:00:00     
(4/10): dracut-config-rescue-033-568.el7.x86_64.rpm                                                                   |  60 kB  00:00:00     
(5/10): dracut-network-033-568.el7.x86_64.rpm                                                                         | 103 kB  00:00:00     
(6/10): initscripts-9.49.49-1.el7.x86_64.rpm                                                                          | 440 kB  00:00:00     
(7/10): libgudev1-219-73.el7_8.5.x86_64.rpm                                                                           | 106 kB  00:00:00     
(8/10): systemd-libs-219-73.el7_8.5.x86_64.rpm                                                                        | 416 kB  00:00:00     
(9/10): systemd-sysv-219-73.el7_8.5.x86_64.rpm                                                                        |  93 kB  00:00:00     
(10/10): systemd-219-73.el7_8.5.x86_64.rpm                                                                            | 5.1 MB  00:00:00     
---------------------------------------------------------------------------------------------------------------------------------------------
Total                                                                                                         23 MB/s | 6.9 MB  00:00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Updating   : systemd-libs-219-73.el7_8.5.x86_64                                                                                       1/22
  Updating   : centos-release-7-8.2003.0.el7.centos.x86_64                                                                              2/22
  Updating   : cryptsetup-libs-2.0.3-6.el7.x86_64                                                                                       3/22
  Updating   : systemd-219-73.el7_8.5.x86_64                                                                                            4/22
  Updating   : dracut-033-568.el7.x86_64                                                                                                5/22
  Updating   : dracut-config-rescue-033-568.el7.x86_64                                                                                  6/22
  Updating   : dracut-network-033-568.el7.x86_64                                                                                        7/22
  Updating   : initscripts-9.49.49-1.el7.x86_64                                                                                         8/22
  Updating   : systemd-sysv-219-73.el7_8.5.x86_64                                                                                       9/22
  Updating   : libgudev1-219-73.el7_8.5.x86_64                                                                                         10/22

UPGRADE: Automatically re-enabling default systemd units:
        brandbot.path
        rhel-autorelabel.service
        rhel-autorelabel-mark.service
        rhel-configure.service
        rhel-dmesg.service
        rhel-domainname.service
        rhel-import-state.service
        rhel-loadmodules.service
        rhel-readonly.service

  Cleanup    : initscripts-9.49.17-1.el7.x86_64                                                                                        11/22
  Cleanup    : libgudev1-208-11.el7.x86_64                                                                                             12/22
  Cleanup    : systemd-sysv-208-11.el7.x86_64                                                                                          13/22
  Cleanup    : dracut-network-033-161.el7.x86_64                                                                                       14/22
  Cleanup    : dracut-config-rescue-033-161.el7.x86_64                                                                                 15/22
  Cleanup    : centos-release.x86_64                                                                                                   16/22
  Cleanup    : dracut-033-161.el7.x86_64                                                                                               17/22
  Cleanup    : systemd-208-11.el7.x86_64                                                                                               18/22
  Cleanup    : centos-release.x86_64                                                                                                   19/22
  Cleanup    : cryptsetup-libs-1.6.3-2.el7.x86_64                                                                                      20/22
  Cleanup    : systemd-libs.x86_64                                                                                                     21/22
  Cleanup    : systemd-libs.x86_64                                                                                                     22/22
  Verifying  : libgudev1-219-73.el7_8.5.x86_64                                                                                          1/22
  Verifying  : dracut-config-rescue-033-568.el7.x86_64                                                                                  2/22
  Verifying  : centos-release-7-8.2003.0.el7.centos.x86_64                                                                              3/22
  Verifying  : cryptsetup-libs-2.0.3-6.el7.x86_64                                                                                       4/22
  Verifying  : initscripts-9.49.49-1.el7.x86_64                                                                                         5/22
  Verifying  : dracut-033-568.el7.x86_64                                                                                                6/22
  Verifying  : dracut-network-033-568.el7.x86_64                                                                                        7/22
  Verifying  : systemd-sysv-219-73.el7_8.5.x86_64                                                                                       8/22
  Verifying  : systemd-libs-219-73.el7_8.5.x86_64                                                                                       9/22
  Verifying  : systemd-219-73.el7_8.5.x86_64                                                                                           10/22
  Verifying  : systemd-libs-219-67.el7_7.2.x86_64                                                                                      11/22
  Verifying  : centos-release-7-7.1908.0.el7.centos.x86_64                                                                             12/22
  Verifying  : dracut-config-rescue-033-161.el7.x86_64                                                                                 13/22
  Verifying  : systemd-sysv-208-11.el7.x86_64                                                                                          14/22
  Verifying  : dracut-033-161.el7.x86_64                                                                                               15/22
  Verifying  : initscripts-9.49.17-1.el7.x86_64                                                                                        16/22
  Verifying  : systemd-libs-208-11.el7.x86_64                                                                                          17/22
  Verifying  : systemd-208-11.el7.x86_64                                                                                               18/22
  Verifying  : dracut-network-033-161.el7.x86_64                                                                                       19/22
  Verifying  : libgudev1-208-11.el7.x86_64                                                                                             20/22
  Verifying  : centos-release-7-0.1406.el7.centos.2.3.x86_64                                                                           21/22
  Verifying  : cryptsetup-libs-1.6.3-2.el7.x86_64                                                                                      22/22

Updated:
  centos-release.x86_64 0:7-8.2003.0.el7.centos           dracut.x86_64 0:033-568.el7           initscripts.x86_64 0:9.49.49-1.el7          
  systemd.x86_64 0:219-73.el7_8.5                        

Dependency Updated:
  cryptsetup-libs.x86_64 0:2.0.3-6.el7         dracut-config-rescue.x86_64 0:033-568.el7         dracut-network.x86_64 0:033-568.el7         
  libgudev1.x86_64 0:219-73.el7_8.5            systemd-libs.x86_64 0:219-73.el7_8.5              systemd-sysv.x86_64 0:219-73.el7_8.5        

Complete!
[root@systemd]# systemctl status network
network.service - LSB: Bring up/down networking
   Loaded: loaded (/etc/rc.d/init.d/network; bad; vendor preset: disabled)
   Active: inactive (dead)
     Docs: man:systemd-sysv-generator(8)