为什么我在运行时得到一个空列表yum updateinfo：
$ yum updateinfo
Loaded plugins: fastestmirror, ovl
Loading mirror speeds from cached hostfile
* base: centos.mirror.ate.info
* epel: fedora.tu-chemnitz.de
* extras: centos.mirror.ate.info
* updates: ftp.rezopole.net
updateinfo summary done
但是，在执行时yum check-update，我看到一些可用的更新：
[root@instance /]# yum check-update
Loaded plugins: fastestmirror, ovl
Loading mirror speeds from cached hostfile
epel/x86_64/metalink | 28 kB 00:00:00
* base: centos.crazyfrogs.org
* epel: mirror.karneval.cz
* extras: centos.crazyfrogs.org
* updates: mir01.syntis.net
base | 3.6 kB 00:00:00
epel | 5.4 kB 00:00:00
extras | 2.9 kB 00:00:00
updates | 2.9 kB 00:00:00
(1/7): base/7/x86_64/group_gz | 165 kB 00:00:00
(2/7): epel/x86_64/group_gz | 90 kB 00:00:00
(3/7): extras/7/x86_64/primary_db | 153 kB 00:00:00
(4/7): epel/x86_64/primary_db | 6.9 MB 00:00:00
(5/7): base/7/x86_64/primary_db | 6.0 MB 00:00:03
(6/7): epel/x86_64/updateinfo | 1.0 MB 00:00:04
(7/7): updates/7/x86_64/primary_db | 5.8 MB 00:00:03
nss.x86_64 3.44.0-7.el7_7 updates
nss-softokn.x86_64 3.44.0-8.el7_7 updates
nss-softokn-freebl.x86_64 3.44.0-8.el7_7 updates
nss-sysinit.x86_64 3.44.0-7.el7_7 updates
nss-tools.x86_64 3.44.0-7.el7_7 updates
nss-util.x86_64 3.44.0-4.el7_7 updates
答案1
yum updateinfo列出了可更新的软件包的建议。示例输出是：
Loaded plugins: fastestmirror, ovl
Loading mirror speeds from cached hostfile
* base: centos.mirror.ate.info
* epel: fedora.tu-chemnitz.de
* extras: centos.mirror.ate.info
* updates: ftp.rezopole.net
Updates Information Summary: available
3 Security notice(s)
1 Important Security notice(s)
2 Moderate Security notice(s)
1 Bugfix notice(s)
updateinfo summary done
另一方面，yum check-update列出了您的软件包可用的所有更新。通常，只有当您需要额外的功能时，您才会升级到这些，而不是出于安全原因。