Where does Yum to find Errata?

1. Yum repo directory layout

Let's take the baseos repo of RockyLinux 8 for example.

$ curl -L http://mirrors.wolfpaw.com/rocky/8.4/BaseOS/x86_64/os/repodata/repomd.xml

<?xml version="1.0" encoding="UTF-8"?>

<repomd xmlns="http://linux.duke.edu/metadata/repo" xmlns:rpm="http://linux.duke.edu/metadata/rpm">

  <revision>8.4</revision>

  <tags>

    <distro cpeid="cpe:/o:rocky:rocky:8">Rocky Linux 8</distro>

  </tags>

  <data type="primary">

    <checksum type="sha256">a82986d2dc78a8782bee08761e7b0816e99f577600f3aabb2a735a8a60976a3a</checksum>

    <open-checksum type="sha256">47c26574da3868163467ea9ba28e8592ba7b21a4e14a94393d699d596ff9b82b</open-checksum>

    <location href="repodata/a82986d2dc78a8782bee08761e7b0816e99f577600f3aabb2a735a8a60976a3a-primary.xml.gz"></location>

    <timestamp>1629150755</timestamp>

    <size>2940001</size>

    <open-size>21916299</open-size>

  </data>

  <data type="filelists">

    <checksum type="sha256">5a1b5a1c35a29b10ed0c2970938ab2b11ff011daa8d2b837f004a8fb0de0ce3d</checksum>

    <open-checksum type="sha256">dcbb682a35ae941c30e1dc7dce0c209788b6592bd5f96f79b7e533aef2735aeb</open-checksum>

    <location href="repodata/5a1b5a1c35a29b10ed0c2970938ab2b11ff011daa8d2b837f004a8fb0de0ce3d-filelists.xml.gz"></location>

    <timestamp>1629150755</timestamp>

    <size>2569812</size>

    <open-size>34364242</open-size>

  </data>

  <data type="other">

    <checksum type="sha256">048c5da9000c00de59c4ba19847b73b5bbf693f574dbcea9e91fb1e2e4000dc4</checksum>

    <open-checksum type="sha256">1b879d1bbb13a2e277eef4080b09c817554fac98759df8a7e76f25813c5a9f73</open-checksum>

    <location href="repodata/048c5da9000c00de59c4ba19847b73b5bbf693f574dbcea9e91fb1e2e4000dc4-other.xml.gz"></location>

    <timestamp>1629150755</timestamp>

    <size>521326</size>

    <open-size>5696853</open-size>

  </data>

  <data type="primary_db">

    <checksum type="sha256">74c205ec5ecf5f3f1d46918823fafce2909df1d89d7fe31033739a6f2a3d56a1</checksum>

    <open-checksum type="sha256">f2c09c4ae7d7b69aff23fa61315afc54a1d2b36032ffb8a78d47428aad272f20</open-checksum>

    <location href="repodata/74c205ec5ecf5f3f1d46918823fafce2909df1d89d7fe31033739a6f2a3d56a1-primary.sqlite.xz"></location>

    <timestamp>1629150765</timestamp>

    <size>2980744</size>

    <open-size>24973312</open-size>

  </data>

  <data type="filelists_db">

    <checksum type="sha256">d69ed31988c9473f97cbf9e0b4e6f69c92006a71581457da40eb40c844a6e85d</checksum>

    <open-checksum type="sha256">f8a5303398b39ce736d672ee23c8eaa9623d70bf84b665cb1347ae025a3fe4f8</open-checksum>

    <location href="repodata/d69ed31988c9473f97cbf9e0b4e6f69c92006a71581457da40eb40c844a6e85d-filelists.sqlite.xz"></location>

    <timestamp>1629150760</timestamp>

    <size>2208888</size>

    <open-size>18841600</open-size>

  </data>

  <data type="other_db">

    <checksum type="sha256">268a7226fa06f483f97f777164d5854fd463a5be5e2054f4eebe34bfa550e17c</checksum>

    <open-checksum type="sha256">e92645d8478ccdf41d564d916b31f9f9b06568d2baff12eb5b5b26f642f85aa2</open-checksum>

    <location href="repodata/268a7226fa06f483f97f777164d5854fd463a5be5e2054f4eebe34bfa550e17c-other.sqlite.xz"></location>

    <timestamp>1629150757</timestamp>

    <size>416788</size>

    <open-size>5574656</open-size>

  </data>

  <data type="group">

    <checksum type="sha256">5eedac6f334681aa51e154d77025db287c33ce1491b14368be9b477ff8208152</checksum>

    <location href="repodata/5eedac6f334681aa51e154d77025db287c33ce1491b14368be9b477ff8208152-comps-BaseOS.x86_64.xml"></location>

    <timestamp>1629150745</timestamp>

    <size>297208</size>

  </data>

  <data type="group_xz">

    <checksum type="sha256">32e04847f7cc2872db5ac9e92ea540ef2a7999d1c2be0c8c3d47a359b3e2d613</checksum>

    <open-checksum type="sha256">5eedac6f334681aa51e154d77025db287c33ce1491b14368be9b477ff8208152</open-checksum>

    <location href="repodata/32e04847f7cc2872db5ac9e92ea540ef2a7999d1c2be0c8c3d47a359b3e2d613-comps-BaseOS.x86_64.xml.xz"></location>

    <timestamp>1629150755</timestamp>

    <size>56668</size>

    <open-size>297208</open-size>

  </data>

  <data type="updateinfo">

    <checksum type="sha256">66f0c44dfe2035ad59bec8462ad3607424d9b4255b7a3d42d0782777ae247a71</checksum>

    <open-checksum type="sha256">1a896935db4b0201697e895aaf22a40023549a44102aa7fbe3af1be3f6fe1a6b</open-checksum>

    <location href="repodata/66f0c44dfe2035ad59bec8462ad3607424d9b4255b7a3d42d0782777ae247a71-updateinfo.xml.gz"></location>

    <timestamp>1629158458</timestamp>

    <size>23375</size>

    <open-size>175696</open-size>

  </data>

</repomd>

2. The main file "./repodata/repomd.xml"

3. xxx-primary.xml

4. xxx-filelists.xml

5. xxx-updateinfo.xml (Errata)

This file is where the Errata are located. Errata is the info about a security level update that involves a certain group of rpm packages. In production env, "update all installed packages at the same time" is usually not the choice, instead, only certain packages related to a security issue are to be updated. This is the reason why "Errata" exists. 

$ curl -L http://mirrors.wolfpaw.com/rocky/8.4/BaseOS/x86_64/os/repodata/66f0c44dfe2035ad59bec8462ad3607424d9b4255b7a3d42d0782777ae247a71-updateinfo.xml.gz | gunzip

<updates>

  <update from="releng@rockylinux.org" status="final" type="bugfix" version="2">

    <id>RLBA-2021:3050</id>

    <title>samba bug fix and enhancement update</title>

    <issued date="2021-08-12 21:15:04"></issued>

    <updated date="2021-08-10 00:00:00"></updated>

    <rights>Copyright (C) 2021 Rocky Enterprise Software Foundation</rights>

    <release>Rocky Linux 8</release>

    <pushcount>1</pushcount>

    <severity>None</severity>

    <summary>An update for samba is now available for Rocky Linux 8.</summary>

    <description>For more information visit https://errata.rockylinux.org/RLBA-2021:3050</description>

    <references>

      <reference href="https://access.redhat.com/errata/RHBA-2021:3050" id="RHBA-2021:3050" type="erratum" title="Update information for RHBA-2021:3050 is retrieved from Red Hat"></reference>

    </references>

    <pkglist>

      <collection short="RL8">

        <name>Rocky Linux 8</name>

        <package name="ctdb" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>ctdb-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">07b27ba2f4e4866648779871ccb251336919d4e0cd585fb505dcceaec2b521ff</sum>

        </package>

        <package name="ctdb-tests" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>ctdb-tests-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">8aba09c2ac5639febe3ac6a611a746cfdd652fbecc7631f93cc8f10bda85082e</sum>

        </package>

        <package name="libsmbclient" version="4.13.3" release="4.el8_4" epoch="0" arch="i686" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>libsmbclient-4.13.3-4.el8_4.i686.rpm</filename>

          <sum type="sha256">ac6cb32092e69fdafc08de239819af46039f24fff6c7d1482cc672648970e518</sum>

        </package>

        <package name="libsmbclient" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>libsmbclient-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">552613065eaf4f08591b17d415623f4138b062895478b0991a910d0eaec8e4ac</sum>

        </package>

        <package name="libwbclient" version="4.13.3" release="4.el8_4" epoch="0" arch="i686" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>libwbclient-4.13.3-4.el8_4.i686.rpm</filename>

          <sum type="sha256">21cee6657a53c41b658d7f939cf1ee14775be86f989f3fe4581783a842c54ba5</sum>

        </package>

        <package name="libwbclient" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>libwbclient-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">3a9e43ecac418f5c3b0c6264562e711a687b94f6557d279ccf86ec79fffb72c3</sum>

        </package>

        <package name="python3-samba" version="4.13.3" release="4.el8_4" epoch="0" arch="i686" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>python3-samba-4.13.3-4.el8_4.i686.rpm</filename>

          <sum type="sha256">11c393374b25bbfe4a545685b47fe6e77ea40a7273877e82de66ea2fd7ccdb74</sum>

        </package>

        <package name="python3-samba" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>python3-samba-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">fc37c4d409cb67781cc5740dfef84c2514490fdf0fd8c64957980036a7b33ecc</sum>

        </package>

        <package name="python3-samba-test" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>python3-samba-test-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">198585750562c2018a347fa173fa6320fe6295d6fce25287e501eca387970502</sum>

        </package>

        <package name="samba" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">66f9c8f9b8d6c6e5ba2f50c690fa957261254eaf0ee791fb3aef98d36c35e296</sum>

        </package>

        <package name="samba-client" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-client-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">4ebb8e998a6d528dbd8dcafe007c3628fe716d045f52b00c5ed22d7a77e02690</sum>

        </package>

        <package name="samba-client-libs" version="4.13.3" release="4.el8_4" epoch="0" arch="i686" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-client-libs-4.13.3-4.el8_4.i686.rpm</filename>

          <sum type="sha256">9f4c0733a16a23e4bc4b33c840d661632710b621f47ca3acb0f747a593d09f26</sum>

        </package>

        <package name="samba-client-libs" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-client-libs-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">7c3e148e293b6b88c6d8658df4dbeb7244f07b96b5237b285ca72acc3cacba7c</sum>

        </package>

        <package name="samba-common" version="4.13.3" release="4.el8_4" epoch="0" arch="noarch" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-common-4.13.3-4.el8_4.noarch.rpm</filename>

          <sum type="sha256">6f89322879f8d8e0d596d9f31b21454555eadd6af2529c9db9b20cc3c1ef39cf</sum>

        </package>

        <package name="samba-common-libs" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-common-libs-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">7c680330719de9e9d333ae7007caa799101adb2a74e2c257372d5cc170e9218a</sum>

        </package>

        <package name="samba-common-tools" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-common-tools-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">5ad0067d2f7fc79eda5d53d09c57b067539cb7a004be022ea900519cac3db6ae</sum>

        </package>

        <package name="samba-krb5-printing" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-krb5-printing-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">d2ecbd3da8da3f72842a21fabace2e15544360eb982eb77697b44a3094d63201</sum>

        </package>

        <package name="samba-libs" version="4.13.3" release="4.el8_4" epoch="0" arch="i686" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-libs-4.13.3-4.el8_4.i686.rpm</filename>

          <sum type="sha256">799ce571abfc12152f756866ea40295af065fc71bed9a5bed8649cdfd3ce914b</sum>

        </package>

        <package name="samba-libs" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-libs-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">c18c069de63428cdbb8e30bef479c84af5f86511e283aa6d562ed2cba2e7b6ab</sum>

        </package>

        <package name="samba-pidl" version="4.13.3" release="4.el8_4" epoch="0" arch="noarch" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-pidl-4.13.3-4.el8_4.noarch.rpm</filename>

          <sum type="sha256">c6fc9c3aad802c25ee34eb68f96f0fc67eff8e16e58596f18566fcf36a7a76e8</sum>

        </package>

        <package name="samba-test" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-test-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">bef5f8ce586d14d6a9d7312ffcfbd66a0239e4704831d53159f14ba7a4a8c368</sum>

        </package>

        <package name="samba-test-libs" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-test-libs-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">86fe91cf3951018373f4c97fb7ee81df32e3d01361d4da59153a921bd4f1f534</sum>

        </package>

        <package name="samba-winbind" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-winbind-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">15921bffbed3eae890787e24fa2cf2e94624c80bed3fb782af324c650f6c942d</sum>

        </package>

        <package name="samba-winbind-clients" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-winbind-clients-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">ae78435484de92e7cc2d701fb9e8d1b22a8424cd56ebd2fff0b7615aca236602</sum>

        </package>

        <package name="samba-winbind-krb5-locator" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-winbind-krb5-locator-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">b2dec180af70b13daef123a0e1ba35bfcf5ec45525bd8e7385e3fafa64e29cfa</sum>

        </package>

        <package name="samba-winbind-modules" version="4.13.3" release="4.el8_4" epoch="0" arch="i686" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-winbind-modules-4.13.3-4.el8_4.i686.rpm</filename>

          <sum type="sha256">7c5f14f5fe36c555f01f1b012b62f24362334e2975d88c41ad438de9e75d15a5</sum>

        </package>

        <package name="samba-winbind-modules" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-winbind-modules-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">3e52bc6f93c100148ca983c4b1d7f2d24844b4b6c47179c6c83f51edf63a350f</sum>

        </package>

        <package name="samba-winexe" version="4.13.3" release="4.el8_4" epoch="0" arch="x86_64" src="samba-4.13.3-4.el8_4.src.rpm">

          <filename>samba-winexe-4.13.3-4.el8_4.x86_64.rpm</filename>

          <sum type="sha256">be4a132c54c9392e44327675d2d459f6bf950935dc032e46b30178cff0a3e20e</sum>

        </package>

      </collection>

    </pkglist>

  </update>

.....