Linux pax命令 详解

# 1. 基本创建归档
pax -wf archive.tar file1 file2       # 创建tar归档
pax -wf archive.tar *                 # 归档当前目录所有文件

# 2. 使用特定格式
pax -x cpio -wf archive.cpio file1 file2  # 创建cpio格式
pax -x ustar -wf archive.ustar .          # 创建ustar格式

# 3. 使用压缩
pax -wf archive.tar.gz -z file1 file2     # 创建gzip压缩的tar
pax -wf archive.tar.bz2 -j file1 file2    # 创建bzip2压缩的tar

# 4. 详细模式查看过程
pax -vwf archive.tar file1 file2 dir1/

# 5. 从标准输入读取文件列表
find . -name "*.txt" | pax -wf textfiles.tar

# 6. 排除特定文件
find . -type f ! -name "*.tmp" | pax -wf notmp.tar

# 7. 保留文件属性
pax -wf archive.tar -p e file1 file2      # 保留所有属性

# 8. 创建增量备份（基于时间戳）
pax -wf backup.tar -T 20230101000000 .   # 备份指定时间后的文件

# 9. 归档到远程服务器（通过ssh）
pax -wf - . | ssh user@host 'cat > backup.tar'

# 10. 分卷归档
pax -wf - . | split -b 100M - backup.tar.part

# 1. 基本提取
pax -rf archive.tar                    # 提取到当前目录
pax -rf archive.tar -C /tmp            # 提取到指定目录

# 2. 提取特定格式
pax -rf archive.cpio -x cpio           # 提取cpio格式
pax -rf archive.ustar -x ustar         # 提取ustar格式

# 3. 解压缩提取
pax -rf archive.tar.gz -z              # 提取gzip压缩的tar
pax -rf archive.tar.bz2 -j             # 提取bzip2压缩的tar

# 4. 详细模式查看提取过程
pax -vrf archive.tar

# 5. 选择性提取
pax -rf archive.tar file1              # 只提取file1
pax -rf archive.tar "*.txt"            # 只提取txt文件

# 6. 保留文件属性
pax -rf archive.tar -p e               # 保留所有属性

# 7. 不覆盖已存在文件
pax -rf archive.tar -k                 # -k选项防止覆盖

# 8. 从标准输入读取归档
cat archive.tar | pax -rf -            # 从stdin读取
ssh user@host 'cat backup.tar' | pax -rf -  # 从远程提取

# 9. 列出归档内容而不提取
pax -f archive.tar                     # 列出归档内容
pax -vf archive.tar                    # 详细列出

# 10. 提取并重命名文件
pax -rf archive.tar -s '|oldname|newname|'  # 重命名提取的文件

#!/bin/bash
# 完整的备份和恢复脚本
# 文件名：pax_backup_system.sh

BACKUP_DIR="/backup"
LOG_FILE="/var/log/pax_backup.log"
CONFIG_FILE="/etc/backup.conf"

# 颜色定义
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[0;33m'
NC='\033[0m' # No Color

# 日志函数
log() {
    local level="$1"
    local message="$2"
    local timestamp=$(date "+%Y-%m-%d %H:%M:%S")

    echo "[$timestamp] [$level] $message" | tee -a "$LOG_FILE"
}

# 初始化备份环境
init_backup() {
    log "INFO" "初始化备份环境"

    # 创建备份目录
    mkdir -p "$BACKUP_DIR"/{daily,weekly,monthly}

    # 检查pax命令
    if ! command -v pax &> /dev/null; then
        log "ERROR" "pax命令未找到，请安装"
        exit 1
    fi

    # 加载配置文件
    if [ -f "$CONFIG_FILE" ]; then
        source "$CONFIG_FILE"
    else
        # 默认配置
        BACKUP_SOURCES=(
            "/etc"
            "/home"
            "/var/www"
            "/opt"
        )
        BACKUP_EXCLUDES=(
            "*.tmp"
            "*.log"
            "*.cache"
        )
        RETENTION_DAYS=30
    fi

    log "INFO" "备份环境初始化完成"
}

# 创建完整备份
create_full_backup() {
    local backup_name="full_backup_$(date +%Y%m%d_%H%M%S).tar.gz"
    local backup_path="$BACKUP_DIR/monthly/$backup_name"

    log "INFO" "开始创建完整备份: $backup_name"

    # 创建排除文件列表
    local exclude_file="/tmp/exclude_$$.txt"
    for pattern in "${BACKUP_EXCLUDES[@]}"; do
        echo "$pattern" >> "$exclude_file"
    done

    # 使用pax创建备份
    log "INFO" "收集备份文件..."
    find "${BACKUP_SOURCES[@]}" -type f ! -name "*.tmp" ! -name "*.log" 2>/dev/null | \
        pax -wzf "$backup_path" -d -s "|^/||"

    if [ $? -eq 0 ]; then
        local size=$(du -h "$backup_path" | cut -f1)
        log "SUCCESS" "完整备份创建完成: $backup_name ($size)"

        # 创建校验文件
        md5sum "$backup_path" > "$backup_path.md5"
    else
        log "ERROR" "完整备份创建失败"
    fi

    # 清理
    rm -f "$exclude_file"
}

# 创建增量备份
create_incremental_backup() {
    local backup_name="inc_backup_$(date +%Y%m%d_%H%M%S).tar.gz"
    local backup_path="$BACKUP_DIR/daily/$backup_name"
    local last_backup=$(find "$BACKUP_DIR" -name "*.tar.gz" -type f -printf "%T@ %p\n" | sort -nr | head -1 | cut -d' ' -f2)

    log "INFO" "开始创建增量备份: $backup_name"

    if [ -z "$last_backup" ]; then
        log "WARNING" "未找到之前的备份，创建完整备份"
        create_full_backup
        return
    fi

    # 获取上次备份时间
    local last_time=$(stat -c %Y "$last_backup")

    # 查找上次备份后修改的文件
    log "INFO" "查找自上次备份后修改的文件..."
    find "${BACKUP_SOURCES[@]}" -type f -newer "@$last_time" ! -name "*.tmp" ! -name "*.log" 2>/dev/null | \
        pax -wzf "$backup_path" -d -s "|^/||"

    if [ $? -eq 0 ]; then
        local size=$(du -h "$backup_path" | cut -f1)
        local file_count=$(pax -tzf "$backup_path" | wc -l)
        log "SUCCESS" "增量备份创建完成: $backup_name ($size, $file_count 个文件)"
    else
        log "ERROR" "增量备份创建失败"
    fi
}

# 恢复备份
restore_backup() {
    local backup_file="$1"
    local restore_path="${2:-/}"

    if [ ! -f "$backup_file" ]; then
        log "ERROR" "备份文件不存在: $backup_file"
        return 1
    fi

    log "INFO" "开始恢复备份: $(basename "$backup_file")"
    log "INFO" "恢复到: $restore_path"

    # 验证备份文件
    if [ -f "$backup_file.md5" ]; then
        if ! md5sum -c "$backup_file.md5" &> /dev/null; then
            log "ERROR" "备份文件校验失败，可能已损坏"
            return 1
        fi
    fi

    # 交互式确认
    read -p "确认恢复备份？这将覆盖现有文件。 (y/N): " -n 1 -r
    echo
    if [[ ! $REPLY =~ ^[Yy]$ ]]; then
        log "INFO" "恢复操作已取消"
        return 0
    fi

    # 执行恢复
    log "INFO" "正在恢复文件..."
    if pax -rzf "$backup_file" -C "$restore_path" -p e; then
        log "SUCCESS" "备份恢复完成"

        # 恢复文件权限
        log "INFO" "修复文件权限..."
        restore_permissions "$backup_file" "$restore_path"
    else
        log "ERROR" "备份恢复失败"
        return 1
    fi
}

# 恢复文件权限
restore_permissions() {
    local backup_file="$1"
    local restore_path="$2"

    log "INFO" "从备份中提取权限信息..."

    # 创建临时目录存放权限信息
    local temp_dir="/tmp/restore_perms_$$"
    mkdir -p "$temp_dir"

    # 提取包含权限信息的文件列表
    pax -tzvf "$backup_file" | awk '{print $6, $3, $4, $1}' > "$temp_dir/filelist.txt"

    # 应用权限
    while read -r file mode owner group; do
        # 移除开头的./
        file="${file#./}"

        if [ -f "$restore_path/$file" ]; then
            # 设置权限
            chmod "$mode" "$restore_path/$file" 2>/dev/null || true

            # 设置所有者和组（需要root权限）
            if [ $(id -u) -eq 0 ]; then
                chown "$owner:$group" "$restore_path/$file" 2>/dev/null || true
            fi
        fi
    done < "$temp_dir/filelist.txt"

    rm -rf "$temp_dir"
    log "INFO" "权限恢复完成"
}

# 清理旧备份
cleanup_old_backups() {
    log "INFO" "清理旧备份文件"

    # 清理daily备份（保留7天）
    find "$BACKUP_DIR/daily" -name "*.tar.gz" -mtime +7 -delete
    find "$BACKUP_DIR/daily" -name "*.md5" -mtime +7 -delete

    # 清理weekly备份（保留30天）
    find "$BACKUP_DIR/weekly" -name "*.tar.gz" -mtime +30 -delete
    find "$BACKUP_DIR/weekly" -name "*.md5" -mtime +30 -delete

    # 清理monthly备份（保留365天）
    find "$BACKUP_DIR/monthly" -name "*.tar.gz" -mtime +365 -delete
    find "$BACKUP_DIR/monthly" -name "*.md5" -mtime +365 -delete

    log "INFO" "旧备份清理完成"
}

# 列出可用备份
list_backups() {
    echo "=== 可用备份 ==="
    echo ""

    echo "月度备份:"
    find "$BACKUP_DIR/monthly" -name "*.tar.gz" -type f -printf "  %f (%TY-%Tm-%Td %TH:%TM)\n" 2>/dev/null | sort -r

    echo ""
    echo "周度备份:"
    find "$BACKUP_DIR/weekly" -name "*.tar.gz" -type f -printf "  %f (%TY-%Tm-%Td %TH:%TM)\n" 2>/dev/null | sort -r

    echo ""
    echo "每日备份:"
    find "$BACKUP_DIR/daily" -name "*.tar.gz" -type f -printf "  %f (%TY-%Tm-%Td %TH:%TM)\n" 2>/dev/null | sort -r
}

# 主菜单
main_menu() {
    init_backup

    while true; do
        echo ""
        echo "=== PAX备份管理系统 ==="
        echo "1. 创建完整备份"
        echo "2. 创建增量备份"
        echo "3. 恢复备份"
        echo "4. 列出所有备份"
        echo "5. 清理旧备份"
        echo "6. 查看备份日志"
        echo "7. 退出"
        echo -n "请选择 [1-7]: "

        read -r choice

        case $choice in
            1)
                create_full_backup
                ;;
            2)
                create_incremental_backup
                ;;
            3)
                echo "可用的备份文件:"
                find "$BACKUP_DIR" -name "*.tar.gz" -type f | nl
                echo -n "请输入备份编号: "
                read -r backup_num

                backups=($(find "$BACKUP_DIR" -name "*.tar.gz" -type f | sort))
                selected="${backups[$((backup_num-1))]}"

                if [ -n "$selected" ]; then
                    echo -n "请输入恢复路径 (默认: /): "
                    read -r restore_path
                    restore_backup "$selected" "${restore_path:-/}"
                else
                    echo "无效的选择"
                fi
                ;;
            4)
                list_backups
                ;;
            5)
                cleanup_old_backups
                ;;
            6)
                echo "=== 备份日志 ==="
                tail -50 "$LOG_FILE"
                ;;
            7)
                echo "退出"
                exit 0
                ;;
            *)
                echo "无效选择"
                ;;
        esac

        echo ""
        read -p "按回车键继续..." -n1
        clear
    done
}

# 运行主菜单
main_menu