tiup: give a more clear recommendation about SELinux (#20068)

.github/workflows/link-fail-fast.yaml

@@ -17,10 +17,6 @@ jobs:
           CHANGED_FILES=$(git diff-tree --name-only --diff-filter 'AM' -r HEAD^1 HEAD -- "*.md" | sed -z "s/\n$//;s/\n/' '/g")
           echo "all_changed_files=${CHANGED_FILES}" >> $GITHUB_OUTPUT
 
-      - name: Download Exclude Path
-        run: |
-          curl https://raw.githubusercontent.com/pingcap/docs/master/.lycheeignore -O
-
       - name: Link Checker
         if: ${{ steps.changed-files.outputs.all_changed_files }}
         uses: lycheeverse/lychee-action@v1.6.1

.lycheeignore

@@ -14,4 +14,5 @@ file://.*?http:/\$%7BPD_IP%7D:\$%7BPD_PORT%7D/dashboard.*
 http://\{grafana-ip\}:3000
 http://\{pd-ip\}:2379/dashboard
 http://localhost:\d+/
-https://github\.com/\$user/(docs|docs-cn)
+https://github\.com/\$user/(docs|docs-cn)
+https://linux.die.net/man.*

check-before-deployment.md

@@ -707,4 +707,8 @@ sudo yum -y install numactl
 
 ## Disable SELinux
 
-Use the [getenforce(8)](https://linux.die.net/man/8/getenforce) utility to check if SELinux is disabled or set to permissive. SELinux in enforcing mode can cause deployment failures. For instructions on disabling SELinux, refer to your operating system's documentation.
+SELinux must be disabled or set to permissive mode. To check the current status, use the [getenforce(8)](https://linux.die.net/man/8/getenforce) utility.
+
+If SELinux is not disabled, open the `/etc/selinux/config` file, locate the line starting with `SELINUX=`, and change it to `SELINUX=disabled`. After making this change, you need to reboot the system because switching from `enforcing` or `permissive` to `disabled` does not take effect without a reboot.
+
+On some systems (such as Ubuntu), the `/etc/selinux/config` file might not exist, and the getenforce utility might not be installed. In that case, you can skip this step.

tiup/tiup-component-cluster-check.md

@@ -76,7 +76,11 @@ Check the limit values in the `/etc/security/limits.conf` file:
 
 ### SELinux
 
-Check whether SELinux is enabled. It is required to disable SELinux.
+SELinux must be disabled or set to permissive mode. To check the current status, use the [getenforce(8)](https://linux.die.net/man/8/getenforce) utility.
+
+If SELinux is not disabled, open the `/etc/selinux/config` file, locate the line starting with `SELINUX=`, and change it to `SELINUX=disabled`. After making this change, you need to reboot the system because switching from `enforcing` or `permissive` to `disabled` does not take effect without a reboot.
+
+On some systems (such as Ubuntu), the `/etc/selinux/config` file might not exist, and the getenforce utility might not be installed. In that case, you can skip this step.
 
 ### Firewall