當你更新系統時，根據你所在公司的安全策略，有時候可能只需要打上與安全相關的修補程式。大多數情況下，這應該是出於程式相容性方面的考量。那該怎樣實踐呢？有沒有辦法讓 yum 只安裝安全修補程式呢？
答案是肯定的，可以用 yum 包管理器輕鬆實現。
在這篇文章中，我們不但會提供所需的資訊。而且，我們會介紹一些額外的命令，可以幫你獲取指定安全更新的詳實資訊。
希望這樣可以啟發你去了解並修復你列表上的那些漏洞。一旦有安全漏洞被公布，就必須更新受影響的軟體，這樣可以降低系統中的安全風險。
對於 RHEL 或 CentOS 6 系統，執行下面的 Yum 命令 來安裝 yum 安全外掛。
# yum -y install yum-plugin-security在 RHEL 7&8 或是 CentOS 7&8 上面，這個外掛已經是 yum 的一部分了，不用單獨安裝。
要列出全部可用的修補程式（包括安全、Bug 修復以及產品改進），但不安裝它們：
# yum updateinfo list availableLoaded plugins: changelog, package_upload, product-id, search-disabled-repos, : subscription-manager, verify, versionlockRHSA-2014:1031 Important/Sec. 389-ds-base-1.3.1.6-26.el7_0.x86_64RHSA-2015:0416 Important/Sec. 389-ds-base-1.3.3.1-13.el7.x86_64RHBA-2015:0626 bugfix 389-ds-base-1.3.3.1-15.el7_1.x86_64RHSA-2015:0895 Important/Sec. 389-ds-base-1.3.3.1-16.el7_1.x86_64RHBA-2015:1554 bugfix 389-ds-base-1.3.3.1-20.el7_1.x86_64RHBA-2015:1960 bugfix 389-ds-base-1.3.3.1-23.el7_1.x86_64RHBA-2015:2351 bugfix 389-ds-base-1.3.4.0-19.el7.x86_64RHBA-2015:2572 bugfix 389-ds-base-1.3.4.0-21.el7_2.x86_64RHSA-2016:0204 Important/Sec. 389-ds-base-1.3.4.0-26.el7_2.x86_64RHBA-2016:0550 bugfix 389-ds-base-1.3.4.0-29.el7_2.x86_64RHBA-2016:1048 bugfix 389-ds-base-1.3.4.0-30.el7_2.x86_64RHBA-2016:1298 bugfix 389-ds-base-1.3.4.0-32.el7_2.x86_64要統計修補程式的大約數量，執行下面的命令：
# yum updateinfo list available | wc -l11269想列出全部可用的安全修補程式但不安裝，以下命令用來展示你系統裡已安裝和待安裝的推薦修補程式：
# yum updateinfo list security allLoaded plugins: changelog, package_upload, product-id, search-disabled-repos, : subscription-manager, verify, versionlock RHSA-2014:1031 Important/Sec. 389-ds-base-1.3.1.6-26.el7_0.x86_64 RHSA-2015:0416 Important/Sec. 389-ds-base-1.3.3.1-13.el7.x86_64 RHSA-2015:0895 Important/Sec. 389-ds-base-1.3.3.1-16.el7_1.x86_64 RHSA-2016:0204 Important/Sec. 389-ds-base-1.3.4.0-26.el7_2.x86_64 RHSA-2016:2594 Moderate/Sec. 389-ds-base-1.3.5.10-11.el7.x86_64 RHSA-2017:0920 Important/Sec. 389-ds-base-1.3.5.10-20.el7_3.x86_64 RHSA-2017:2569 Moderate/Sec. 389-ds-base-1.3.6.1-19.el7_4.x86_64 RHSA-2018:0163 Important/Sec. 389-ds-base-1.3.6.1-26.el7_4.x86_64 RHSA-2018:0414 Important/Sec. 389-ds-base-1.3.6.1-28.el7_4.x86_64 RHSA-2018:1380 Important/Sec. 389-ds-base-1.3.7.5-21.el7_5.x86_64 RHSA-2018:2757 Moderate/Sec. 389-ds-base-1.3.7.5-28.el7_5.x86_64 RHSA-2018:3127 Moderate/Sec. 389-ds-base-1.3.8.4-15.el7.x86_64 RHSA-2014:1031 Important/Sec. 389-ds-base-libs-1.3.1.6-26.el7_0.x86_64要顯示所有待安裝的安全修補程式：
# yum updateinfo list security all | grep -v "i" RHSA-2014:1031 Important/Sec. 389-ds-base-1.3.1.6-26.el7_0.x86_64 RHSA-2015:0416 Important/Sec. 389-ds-base-1.3.3.1-13.el7.x86_64 RHSA-2015:0895 Important/Sec. 389-ds-base-1.3.3.1-16.el7_1.x86_64 RHSA-2016:0204 Important/Sec. 389-ds-base-1.3.4.0-26.el7_2.x86_64 RHSA-2016:2594 Moderate/Sec. 389-ds-base-1.3.5.10-11.el7.x86_64 RHSA-2017:0920 Important/Sec. 389-ds-base-1.3.5.10-20.el7_3.x86_64 RHSA-2017:2569 Moderate/Sec. 389-ds-base-1.3.6.1-19.el7_4.x86_64 RHSA-2018:0163 Important/Sec. 389-ds-base-1.3.6.1-26.el7_4.x86_64 RHSA-2018:0414 Important/Sec. 389-ds-base-1.3.6.1-28.el7_4.x86_64 RHSA-2018:1380 Important/Sec. 389-ds-base-1.3.7.5-21.el7_5.x86_64 RHSA-2018:2757 Moderate/Sec. 389-ds-base-1.3.7.5-28.el7_5.x86_64要統計全部安全修補程式的大致數量，執行下面的命令：
# yum updateinfo list security all | wc -l3522下面根據已裝軟體列出可更新的安全修補程式。這包括 bugzilla（bug 修復）、CVE（知名漏洞資料庫）、安全更新等：
# yum updateinfo list security或者# yum updateinfo list secLoaded plugins: changelog, package_upload, product-id, search-disabled-repos, : subscription-manager, verify, versionlockRHSA-2018:3665 Important/Sec. NetworkManager-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-adsl-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-bluetooth-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-config-server-1:1.12.0-8.el7_6.noarchRHSA-2018:3665 Important/Sec. NetworkManager-glib-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-libnm-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-ppp-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-team-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-tui-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-wifi-1:1.12.0-8.el7_6.x86_64RHSA-2018:3665 Important/Sec. NetworkManager-wwan-1:1.12.0-8.el7_6.x86_64顯示所有與安全相關的更新，並且返回一個結果來告訴你是否有可用的修補程式：
# yum --security check-updateLoaded plugins: changelog, package_upload, product-id, search-disabled-repos, subscription-manager, verify, versionlockrhel-7-server-rpms | 2.0 kB 00:00:00--> policycoreutils-devel-2.2.5-20.el7.x86_64 from rhel-7-server-rpms excluded (updateinfo)--> smc-raghumalayalam-fonts-6.0-7.el7.noarch from rhel-7-server-rpms excluded (updateinfo)--> amanda-server-3.3.3-17.el7.x86_64 from rhel-7-server-rpms excluded (updateinfo)--> 389-ds-base-libs-1.3.4.0-26.el7_2.x86_64 from rhel-7-server-rpms excluded (updateinfo)--> 1:cups-devel-1.6.3-26.el7.i686 from rhel-7-server-rpms excluded (updateinfo)--> openwsman-client-2.6.3-3.git4391e5c.el7.i686 from rhel-7-server-rpms excluded (updateinfo)--> 1:emacs-24.3-18.el7.x86_64 from rhel-7-server-rpms excluded (updateinfo)--> augeas-libs-1.4.0-2.el7_4.2.i686 from rhel-7-server-rpms excluded (updateinfo)--> samba-winbind-modules-4.2.3-10.el7.i686 from rhel-7-server-rpms excluded (updateinfo)--> tftp-5.2-11.el7.x86_64 from rhel-7-server-rpms excluded (updateinfo)..35 package(s) needed for security, out of 115 availableNetworkManager.x86_64 1:1.12.0-10.el7_6 rhel-7-server-rpmsNetworkManager-adsl.x86_64 1:1.12.0-10.el7_6 rhel-7-server-rpmsNetworkManager-bluetooth.x86_64 1:1.12.0-10.el7_6 rhel-7-server-rpmsNetworkManager-config-server.noarch 1:1.12.0-10.el7_6 rhel-7-server-rpmsNetworkManager-glib.x86_64 1:1.12.0-10.el7_6 rhel-7-server-rpmsNetworkManager-libnm.x86_64 1:1.12.0-10.el7_6 rhel-7-server-rpmsNetworkManager-ppp.x86_64 1:1.12.0-10.el7_6 rhel-7-server-rpms列出所有可用的安全修補程式，並且顯示其詳細資訊：
# yum info-sec..=============================================================================== tzdata bug fix and enhancement update=============================================================================== Update ID : RHBA-2019:0689 Release : 0 Type : bugfix Status : final Issued : 2019-03-28 19:27:44 UTCDescription : The tzdata packages contain data files with rules for various : time zones. : : The tzdata packages have been updated to version : 2019a, which addresses recent time zone changes. : Notably: : : * The Asia/Hebron and Asia/Gaza zones will start : DST on 2019-03-30, rather than 2019-03-23 as : previously predicted. : * Metlakatla rejoined Alaska time on 2019-01-20, : ending its observances of Pacific standard time. : : (BZ#1692616, BZ#1692615, BZ#1692816) : : Users of tzdata are advised to upgrade to these : updated packages. Severity : None如果你想要知道某個更新的具體內容，可以執行下面這個命令：
# yum updateinfo RHSA-2019:0163Loaded plugins: changelog, package_upload, product-id, search-disabled-repos, subscription-manager, verify, versionlockrhel-7-server-rpms | 2.0 kB 00:00:00=============================================================================== Important: kernel security, bug fix, and enhancement update=============================================================================== Update ID : RHSA-2019:0163 Release : 0 Type : security Status : final Issued : 2019-01-29 15:21:23 UTC Updated : 2019-01-29 15:23:47 UTC Bugs : 1641548 - CVE-2018-18397 kernel: userfaultfd bypasses tmpfs file permissions : 1641878 - CVE-2018-18559 kernel: Use-after-free due to race condition in AF_PACKET implementation CVEs : CVE-2018-18397 : CVE-2018-18559Description : The kernel packages contain the Linux kernel, the core of any : Linux operating system. : : Security Fix(es): : : * kernel: Use-after-free due to race condition in : AF_PACKET implementation (CVE-2018-18559) : : * kernel: userfaultfd bypasses tmpfs file : permissions (CVE-2018-18397) : : For more details about the security issue(s), : including the impact, a CVSS score, and other : related information, refer to the CVE page(s) : listed in the References section. : : Bug Fix(es): : : These updated kernel packages include also : numerous bug fixes and enhancements. Space : precludes documenting all of the bug fixes in this : advisory. See the descriptions in the related : Knowledge Article: : https://access.redhat.com/articles/3827321 Severity : Importantupdateinfo info done跟之前類似，你可以只查詢那些通過 CVE 釋出的系統漏洞：
# yum updateinfo list cvesLoaded plugins: changelog, package_upload, product-id, search-disabled-repos, : subscription-manager, verify, versionlockCVE-2018-15688 Important/Sec. NetworkManager-1:1.12.0-8.el7_6.x86_64CVE-2018-15688 Important/Sec. NetworkManager-adsl-1:1.12.0-8.el7_6.x86_64CVE-2018-15688 Important/Sec. NetworkManager-bluetooth-1:1.12.0-8.el7_6.x86_64CVE-2018-15688 Important/Sec. NetworkManager-config-server-1:1.12.0-8.el7_6.noarchCVE-2018-15688 Important/Sec. NetworkManager-glib-1:1.12.0-8.el7_6.x86_64CVE-2018-15688 Important/Sec. NetworkManager-libnm-1:1.12.0-8.el7_6.x86_64CVE-2018-15688 Important/Sec. NetworkManager-ppp-1:1.12.0-8.el7_6.x86_64CVE-2018-15688 Important/Sec. NetworkManager-team-1:1.12.0-8.el7_6.x86_64你也可以檢視那些跟 bug 修復相關的更新，執行下面的命令：
# yum updateinfo list bugfix | lessLoaded plugins: changelog, package_upload, product-id, search-disabled-repos, : subscription-manager, verify, versionlockRHBA-2018:3349 bugfix NetworkManager-1:1.12.0-7.el7_6.x86_64RHBA-2019:0519 bugfix NetworkManager-1:1.12.0-10.el7_6.x86_64RHBA-2018:3349 bugfix NetworkManager-adsl-1:1.12.0-7.el7_6.x86_64RHBA-2019:0519 bugfix NetworkManager-adsl-1:1.12.0-10.el7_6.x86_64RHBA-2018:3349 bugfix NetworkManager-bluetooth-1:1.12.0-7.el7_6.x86_64RHBA-2019:0519 bugfix NetworkManager-bluetooth-1:1.12.0-10.el7_6.x86_64RHBA-2018:3349 bugfix NetworkManager-config-server-1:1.12.0-7.el7_6.noarchRHBA-2019:0519 bugfix NetworkManager-config-server-1:1.12.0-10.el7_6.noarch要想得到待安裝更新的摘要資訊，執行這個：
# yum updateinfo summaryLoaded plugins: changelog, package_upload, product-id, search-disabled-repos, subscription-manager, verify, versionlockrhel-7-server-rpms | 2.0 kB 00:00:00Updates Information Summary: updates 13 Security notice(s) 9 Important Security notice(s) 3 Moderate Security notice(s) 1 Low Security notice(s) 35 Bugfix notice(s) 1 Enhancement notice(s)updateinfo summary done如果只想列印出低階別的安全更新，執行下面這個命令。類似的，你也可以只查詢重要級別和中等級別的安全更新。
# yum updateinfo list sec | grep -i "Low"RHSA-2019:0201 Low/Sec. libgudev1-219-62.el7_6.3.x86_64RHSA-2019:0201 Low/Sec. systemd-219-62.el7_6.3.x86_64RHSA-2019:0201 Low/Sec. systemd-libs-219-62.el7_6.3.x86_64RHSA-2019:0201 Low/Sec. systemd-sysv-219-62.el7_6.3.x86_64