add gitlab installtion doc

Code Management/Git/Gitlab/Install/baremetal.md

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+# Setting Up GitLab CE on Ubuntu
+
+Follow the steps below to install and configure GitLab Community Edition (CE) on your Ubuntu system.
+
+---
+
+## Step 1: Update the System
+Ensure your package lists are up-to-date:
+```bash
+sudo apt update
+```
+
+---
+
+## Step 2: Install Dependencies
+Install required packages for GitLab:
+```bash
+sudo apt install -y ca-certificates curl openssh-server postfix tzdata perl
+```
+
+- **ca-certificates**: Ensures proper SSL certificate handling.
+- **curl**: For downloading files.
+- **openssh-server**: For SSH-based Git operations.
+- **postfix**: Mail transport agent for email notifications.
+- **tzdata**: Time zone data.
+- **perl**: Required by GitLab scripts.
+
+During the installation, configure **Postfix** to match your mail setup. If unsure, select "Internet Site" and provide your domain.
+
+---
+
+## Step 3: Add GitLab's Repository
+Download and run the repository setup script:
+```bash
+curl -LO https://packages.gitlab.com/install/repositories/gitlab/gitlab-ce/script.deb.sh
+sudo bash script.deb.sh
+```
+
+---
+
+## Step 4: Install GitLab CE
+Install the GitLab CE package:
+```bash
+sudo apt install -y gitlab-ce
+```
+
+---
+
+## Step 5: Configure GitLab
+Edit the GitLab configuration file to match your environment:
+```bash
+sudo vim /etc/gitlab/gitlab.rb
+```
+
+- Modify the `external_url` setting to your desired domain or IP.
+
+Save and exit the editor.
+
+---
+
+## Step 6: Apply the Configuration
+Reconfigure GitLab to apply the changes:
+```bash
+sudo gitlab-ctl reconfigure
+```
+
+---
+
+## Step 7: Retrieve the Initial Root Password
+After configuration, retrieve the initial root password:
+```bash
+sudo cat /etc/gitlab/initial_root_password
+```
+
+---
+
+## Notes
+- The default admin username is `root`.
+- Save the password securely and change it after the first login.
+
+---
+
+## Troubleshooting
+- If you encounter issues, consult the [GitLab Documentation](https://docs.gitlab.com) or check logs in `/var/log/gitlab`.
+
+---
+
+Enjoy using GitLab CE!