Create how-to-update-EXAClusterOS-via-CLI.md (#79)

Author: b-mihai

Environment-Management/how-to-update-EXAClusterOS-via-CLI.md

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+# How to update EXAClusterOS using the command line
+
+## Background
+
+That article guides you through the procedure to update the ClusterOS via the command line.
+
+## Prerequisites
+
+SSH root access to the License Server.
+
+Check the [Update Considerations](https://docs.exasol.com/db/7.1/administration/on-premise/upgrade/update_considerations.htm) before any software update.
+
+## Instructions
+
+1. Copy the update packages (both) to the License Server.
+
+    ```shell
+    rsync -avP EXA*.pkg root@{LS_IP}:/tmp/
+    ```
+
+    _or_
+
+    ```shell
+    scp EXA*.pkg root@{LS_IP}:/tmp/
+    ```
+
+2. Make sure **no backup** or **storage recovery** is in progress.
+3. Make sure **EXAoperation is running on the License Server**. Check this in the EXAoperation section.
+4. Go to the Software section and **remove the obsolete EXASolution version(s)**.
+5. [Stop the Database](https://docs.exasol.com/db/7.1/administration/on-premise/manage_database/stop_db.htm).
+6. [Stop the Storage Services](https://docs.exasol.com/db/7.1/administration/on-premise/manage_storage/stop_start_storage_service.htm).
+7. [Stop the Cluster Services on the data nodes](https://docs.exasol.com/db/7.1/administration/on-premise/nodes/actions_on_nodes.htm).
+8. SSH into the LS and create the update directory.
+
+    ```shell
+    mkdir /tmp/exasuite_update/
+    ```
+
+9. Extract the package.
+
+    ```shell
+    tar xf EXAClusterOS-7.1.NN_LS-Update.pkg -C /tmp/exasuite_update/
+    ```
+
+10. Start the EXAClusterOS update.
+
+    ```shell
+    $COS_DIRECTORY/share/exaoperation/scripts/exaclusteros_update.sh /tmp/exasuite_update/EXAClusterOS-7.1.NN_LS-Update-CentOS-7.5.NNNN_x86_64.tar.gz
+    ```
+
+11. Check the EXAopeartion log and look for the start and completion messages.
+
+    ```text
+    tail -f /var/log/logd/EXAoperation.log
+    [2023-12-07 16:03:29.911675] NOTICE: [Software update] Start update process to EXAClusterOS version 7.1.NN.
+    [2023-12-07 16:04:10.064588] NOTICE: [Software update] First part of update process succeeded. Please shutdown databases and nodes and restart license server.
+    ```
+
+12. Apply the CentOS security patch update.
+
+    ```shell
+    apply_os_security_updates /tmp/EXASOL-7.1-CentOS-7-CumulativeUpdate-YYYYMMDDHHMM.pkg
+    ```
+
+    _Note: In case you see a message like this "Dismiss already applied patchlevel YYYYMMDDHHMM", it means there is no update needed, and you can continue the procedure._
+13. Reboot the license node.
+14. Check the Software tab and confirm the new version was successfully applied.
+15. Make sure there is enough space in the root filesystem (`df -h /`). If not, try removing some files to release space.
+16. [Reboot the data nodes](https://docs.exasol.com/db/7.1/administration/on-premise/nodes/actions_on_nodes.htm).
+17. [Start the Storage Services](https://docs.exasol.com/db/7.1/administration/on-premise/manage_storage/stop_start_storage_service.htm).
+18. [Start the Database](https://docs.exasol.com/db/7.1/administration/on-premise/manage_database/start_db.htm).
+
+_We appreciate your input! Share your knowledge by contributing to the Knowledge Base directly in [GitHub](https://github.com/exasol/public-knowledgebase)._