Configuring the update_hosts_linux.sh Script

Modify the configuration in the example script to meet you specific requirements.

Prerequisites

You have completed all preparations.

Procedure

Create a file named update_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:

In the Vim editor, press I to enter insert mode.
Copy and paste the following script code and press Esc.
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"
 
# Hosts content file path: Contains the content to be appended to each target host's /etc/hosts file (must be manually created and configured).
HOSTS_FILE="hosts_content.txt"
DEFAULT_PORT=22
SSH_TIMEOUT=10
 
# Initialize log directory and files
initialize_logs() {
    mkdir -p "$LOG_DIR"
    echo "========================================" >> "$RUN_LOG"
    echo "[INFO] $(date '+%Y-%m-%d %H:%M:%S') - Starting new update execution" >> "$RUN_LOG"
    echo "========================================" >> "$RUN_LOG"
 
    echo "========================================" >> "$ERROR_LOG"
    echo "[INFO] $(date '+%Y-%m-%d %H:%M:%S') - Starting new update execution" >> "$ERROR_LOG"
    echo "========================================" >> "$ERROR_LOG"
 
    echo "========================================" > "$SUMMARY_LOG"
    echo "[INFO] $(date '+%Y-%m-%d %H:%M:%S') - Starting new update execution" >> "$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[@]}"
}
 
# Read hosts content from TXT file
read_hosts_content_from_txt() {
    local txt_file="$1"
    if [ -f "$txt_file" ]; then
        cat "$txt_file"
    else
        log_error "Hosts content file '$txt_file' not found."
        exit 1
    fi
}
 
# Initialize log files
initialize_logs
 
# Read server information from CSV file
servers=($(read_servers_from_csv "$CSV_FILE"))
 
# Read hosts content from TXT file
hosts_content=$(read_hosts_content_from_txt "$HOSTS_FILE")
 
# Counters for success and failure
success_count=0
failure_count=0
failed_servers=()
 
# Iterate over each server and push hosts content
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 update 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
 
# Append new Migration-proxy section
echo "$hosts_content" >> /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 "Updated hosts on $ip:$port successfully"
    ((success_count++))
  else
    ssh_error=$(cat "$ssh_output")
    case $ssh_status in
      1)
        log_error "General error occurred while updating hosts on $ip:$port: $ssh_error"
        ;;
      2)
        log_error "Misuse of shell builtins while updating 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 updating 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 Update Summary
========================================
Total number of servers: $total_count
Number of successful updates: $success_count
Number of failed updates: $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."

Modify the following parameters in the script to meet your needs:
- LOG_DIR="/var/log/update_hosts"
  - Description: log directory, which is used to store run, error, and summary logs.
  - Default value: /var/log/update_hosts
  - Suggestion: Change the value to a directory for which the current user has the write permission.
  - Example: LOG_DIR="/home/username/update_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: CSV_FILE="/home/username/configs/servers.csv"
- HOSTS_FILE="hosts_content.txt"
  - Description: hosts file path. The file contains the content to be added to the /etc/hosts file on the source servers.
  - Default value: hosts_content.txt
  - Suggestion: Use an absolute path or a correct relative path.
  - Example: HOSTS_FILE="/home/username/configs/hosts_content.txt"
After the configuration items are modified and saved, run the script in a terminal window. If a GUI is available, press Ctrl+Alt+T to open the terminal.
```
./update_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.