Configuring the rollback_hosts_linux.sh Script

Prerequisites

You have completed all preparations.

Procedure

1. Create a file named rollback_hosts_linux.sh on the server where the script is executed, and copy the following script content to the file. If you have connected to the Linux source servers through SSH, you can directly use vim to create and edit a script file. The procedure is as follows:
   1. In the Vim editor, press I to enter insert mode.
   2. Copy and paste the following script code and press Esc.
   3. Run :wq to save and exit.

   #!/bin/bash
    
   # Configuration
    
   # Log directory path: Used to store run logs, error logs, and summary logs.
   # If the directory doesn't exist, the script will create it automatically.
   LOG_DIR="/var/log/update_hosts"
    
   # Run log file path: Records detailed information about the script's execution.
   RUN_LOG="$LOG_DIR/run.log"
    
   # Error log file path: Records any errors that occur during the script's execution.
   ERROR_LOG="$LOG_DIR/error.log"
    
   # Summary log file path: Records a summary of the script's execution, including the number of successful and failed servers.
   SUMMARY_LOG="$LOG_DIR/summary.log"
    
   # CSV file path: Contains information about the target hosts (must be manually created and configured).
   CSV_FILE="target_servers.csv"
   DEFAULT_PORT=22
   SSH_TIMEOUT=10
    
   # Initialize log directory and files
   initialize_logs() {
       mkdir -p "$LOG_DIR"
       echo "========================================" >> "$RUN_LOG"
       echo "[INFO] $(date '+%Y-%m-%d %H:%M:%S') - Starting new rollback execution" >> "$RUN_LOG"
       echo "========================================" >> "$RUN_LOG"
    
       echo "========================================" >> "$ERROR_LOG"
       echo "[INFO] $(date '+%Y-%m-%d %H:%M:%S') - Starting new rollback execution" >> "$ERROR_LOG"
       echo "========================================" >> "$ERROR_LOG"
    
       echo "========================================" > "$SUMMARY_LOG"
       echo "[INFO] $(date '+%Y-%m-%d %H:%M:%S') - Starting new rollback execution" >> "$SUMMARY_LOG"
       echo "========================================" >> "$SUMMARY_LOG"
   }
    
   # Log info function
   log_info() {
       echo "[INFO] $(date '+%Y-%m-%d %H:%M:%S') - $1" | tee -a "$RUN_LOG"
   }
    
   # Log error function
   log_error() {
       echo "[ERROR] $(date '+%Y-%m-%d %H:%M:%S') - $1" | tee -a "$RUN_LOG" "$ERROR_LOG"
   }
    
   # Read server information from CSV file
   read_servers_from_csv() {
       local csv_file="$1"
       local servers=()
       local header_skipped=false
    
       if [ ! -f "$csv_file" ]; then
           log_error "CSV file '$csv_file' not found."
           exit 1
       fi
    
       # Ensure file ends with a newline character
       sed -i -e '$a\' "$csv_file"
    
       while IFS=, read -r username ip port password; do
           # Skip header row
           if [ "$header_skipped" = false ]; then
               header_skipped=true
               continue
           fi
           # Skip empty and invalid rows
           if [[ -z "$username" || -z "$ip" ]]; then
               continue
           fi
           port=${port:-$DEFAULT_PORT} # Use default port 22
           # Ensure port is numeric
           if ! [[ "$port" =~ ^[0-9]+$ ]]; then
               log_error "Invalid port '$port' for $username@$ip. Skipping this server."
               continue
           fi
           servers+=("$username@$ip:$port:$password")
       done < "$csv_file"
    
       echo "${servers[@]}"
   }
    
   # Initialize log files
   initialize_logs
    
   # Read server information from CSV file
   servers=($(read_servers_from_csv "$CSV_FILE"))
    
   # Counters for success and failure
   success_count=0
   failure_count=0
   failed_servers=()
    
   # Iterate over each server and execute rollback
   for server in "${servers[@]}"; do
     # Extract user, IP, port, and password information
     IFS=':' read -r user_host port pass <<< "$server"
     IFS='@' read -r user ip <<< "$user_host"
     
     log_info "Starting rollback for $user@$ip:$port"
    
     # Create temporary script and SSH_ASKPASS script
     tmp_script=$(mktemp)
     askpass_script=$(mktemp)
    
     cat <<EOF > "$tmp_script"
   #!/bin/bash
   # Backup hosts file
   if [ ! -f /etc/hosts.bak ]; then
     cp /etc/hosts /etc/hosts.bak
   fi
    
   # Remove old Migration-proxy section
   sed -i '/#Migration-proxy-start/,/#Migration-proxy-end/d' /etc/hosts
   EOF
    
     cat <<EOF > "$askpass_script"
   #!/bin/bash
   echo "$pass"
   EOF
    
     chmod +x "$tmp_script" "$askpass_script"
    
     # Set SSH_ASKPASS environment variable and use ssh to connect to the target machine and execute the temporary script
     export SSH_ASKPASS="$askpass_script"
     export DISPLAY=:0
    
     ssh_output=$(mktemp)
     setsid ssh -o BatchMode=no -o ConnectTimeout=$SSH_TIMEOUT -o StrictHostKeyChecking=no -p "$port" "$user@$ip" 'bash -s' < "$tmp_script" 2> "$ssh_output"
     ssh_status=$?
    
     if [ $ssh_status -eq 0 ]; then
       log_info "Rolled back hosts on $ip:$port successfully"
       ((success_count++))
     else
       ssh_error=$(cat "$ssh_output")
       case $ssh_status in
         1)
           log_error "General error occurred while rolling back hosts on $ip:$port: $ssh_error"
           ;;
         2)
           log_error "Misuse of shell builtins while rolling back hosts on $ip:$port: $ssh_error"
           ;;
         255)
           if [[ "$ssh_error" == *"Permission denied"* ]]; then
             log_error "SSH login failed for $user@$ip:$port: Permission denied (password may be incorrect or username is wrong)"
           elif [[ "$ssh_error" == *"Connection refused"* ]]; then
             log_error "SSH login failed for $user@$ip:$port: Connection refused (port may be incorrect or SSH service not running on target)"
           elif [[ "$ssh_error" == *"No route to host"* ]]; then
             log_error "SSH login failed for $user@$ip:$port: No route to host (network unreachable)"
           elif [[ "$ssh_error" == *"Host key verification failed"* ]]; then
             log_error "SSH login failed for $user@$ip:$port: Host key verification failed"
           elif [[ "$ssh_error" == *"Connection timed out"* ]]; then
             log_error "SSH login failed for $user@$ip:$port: Connection timed out"
           else
             log_error "SSH login failed for $user@$ip:$port: $ssh_error"
           fi
           ;;
         *)
           log_error "An unknown error occurred while rolling back hosts on $ip:$port: $ssh_error"
           ;;
       esac
       failed_servers+=("$user@$ip:$port")
       ((failure_count++))
     fi
    
     # Remove temporary scripts and SSH output file
     rm -f "$tmp_script" "$askpass_script" "$ssh_output"
   done
    
   # Calculate failure and success percentages
   total_count=${#servers[@]}
   failure_percentage=$(echo "scale=2; ($failure_count / $total_count) * 100" | bc)
   success_percentage=$(echo "scale=2; ($success_count / $total_count) * 100" | bc)
    
   # Output summary result and log to file
   summary_content=$(cat <<EOF
   ========================================
   [SUMMARY] $(date '+%Y-%m-%d %H:%M:%S') - Execution Rollback Summary
   ========================================
   Total number of servers: $total_count
   Number of successful rollbacks: $success_count
   Number of failed rollbacks: $failure_count
   Success rate: $success_percentage%
   Failure rate: $failure_percentage%
   ----------------------------------------
   EOF
   )
    
   if [ $failure_count -gt 0 ]; then
       summary_content+="Failed servers:\n"
       for server in "${failed_servers[@]}"; do
           summary_content+="  - $server\n"
       done
   fi
   summary_content+="========================================"
    
   # Output summary result to log file and terminal
   echo -e "$summary_content" | tee -a "$SUMMARY_LOG"
    
   log_info "Script execution completed. Check $SUMMARY_LOG for summary."

2. Modify the following parameters in the script to meet your needs:
   • LOG_DIR="/var/log/rollback_hosts"
     • Description: log directory
     • Default value: /var/log/rollback_hosts
     • Suggestion: Change the value to a directory for which the current user has the write permission.
     • Example: LOG_DIR="/home/username/rollback_hosts_logs"
   • CSV_FILE="target_servers.csv"
     • Description: CSV file path. The file contains the source server information.
     • Default value: target_servers.csv
     • Suggestion: Use an absolute path or a correct relative path.
     • Example value: CSV_FILE="/home/username/configs/servers.csv"

3. Saving the changes. Run the script in a terminal window. If a GUI is available, press Ctrl+Alt+T to open the terminal.

   ./rollback_hosts_linux.sh

   The script will output log information in the terminal window and generate a result report upon completion. You can view this report in the summary.log file in the directory specified by LOG_DIR.