添加swap交换空间的交互式脚本

```bash
#!/bin/sh

set -eu

SCRIPT_NAME=${0##*/}
FSTAB=${ADD_SWAP_FSTAB:-/etc/fstab}
PROC_SWAPS=${ADD_SWAP_PROC_SWAPS:-/proc/swaps}
MEMINFO=${ADD_SWAP_MEMINFO:-/proc/meminfo}
OS_RELEASE=${ADD_SWAP_OS_RELEASE:-/etc/os-release}
SWAP_FILE=
SIZE_MIB=0
CREATED=0
ACTIVE=0
FSTAB_MODIFIED=0
FSTAB_BACKUP=
DONE=0

info() {
    printf '%s\n' "[信息] $*"
}

warn() {
    printf '%s\n' "[警告] $*" >&2
}

die() {
    printf '%s\n' "[错误] $*" >&2
    exit 1
}

ask() {
    prompt=$1
    default=$2

if [ -t 0 ] && [ -r /dev/tty ]; then
        printf '%s' "$prompt" >/dev/tty
        IFS= read -r answer </dev/tty || answer=
    else
        printf '%s' "$prompt"
        IFS= read -r answer || answer=
    fi

if [ -z "$answer" ]; then
        answer=$default
    fi
    REPLY=$answer
}

confirm() {
    prompt=$1
    default=${2:-n}

if [ "$default" = y ]; then
        suffix='[Y/n] '
    else
        suffix='[y/N] '
    fi

ask "$prompt $suffix" "$default"
    case "$REPLY" in
        y|Y|yes|YES|Yes) return 0 ;;
        *) return 1 ;;
    esac
}

command_exists() {
    command -v "$1" >/dev/null 2>&1
}

is_active_swap() {
    awk -v path="$1" 'NR > 1 && $1 == path { found = 1 } END { exit !found }' "$PROC_SWAPS"
}

path_in_fstab() {
    [ -f "$FSTAB" ] || return 1
    awk -v path="$1" '$1 == path && $3 == "swap" { found = 1 } END { exit !found }' "$FSTAB"
}

cleanup() {
    status=$?
    trap - 0 1 2 15

if [ "$DONE" -ne 1 ]; then
        if [ "$FSTAB_MODIFIED" -eq 1 ] && [ -n "$FSTAB_BACKUP" ] && [ -f "$FSTAB_BACKUP" ]; then
            cp -p "$FSTAB_BACKUP" "$FSTAB" || warn "无法恢复 $FSTAB，请手动检查。"
        fi
        if [ -n "$SWAP_FILE" ] && { [ "$ACTIVE" -eq 1 ] || is_active_swap "$SWAP_FILE"; }; then
            swapoff "$SWAP_FILE" >/dev/null 2>&1 || warn "无法停用 $SWAP_FILE，请手动处理。"
        fi
        if [ "$CREATED" -eq 1 ]; then
            rm -f "$SWAP_FILE" || warn "无法删除 $SWAP_FILE，请手动处理。"
        fi
    fi

if [ -n "$FSTAB_BACKUP" ] && [ -f "$FSTAB_BACKUP" ]; then
        rm -f "$FSTAB_BACKUP"
    fi
    exit "$status"
}

trap cleanup 0
trap 'exit 130' 1 2 15

if [ "$(id -u)" -ne 0 ]; then
    if command_exists sudo && [ -f "$0" ]; then
        info "需要 root 权限，正在通过 sudo 重新运行。"
        trap - 0 1 2 15
        exec sudo -- sh "$0" "$@"
    fi
    die "请以 root 身份运行：sudo sh $SCRIPT_NAME"
fi

OS_ID=unknown
OS_NAME=Linux
if [ -r "$OS_RELEASE" ]; then
    OS_ID=$(sed -n 's/^ID=//p' "$OS_RELEASE" | head -n 1 | tr -d '"')
    OS_NAME=$(sed -n 's/^PRETTY_NAME=//p' "$OS_RELEASE" | head -n 1 | sed 's/^"//; s/"$//')
fi
info "检测到系统：$OS_NAME"

install_util_linux() {
    warn "系统缺少创建 swap 所需的 util-linux 工具。"
    confirm "是否现在安装？" y || die "缺少 mkswap、swapon 或 findmnt。"

if command_exists apt-get; then
        apt-get update
        DEBIAN_FRONTEND=noninteractive apt-get install -y util-linux
    elif command_exists dnf; then
        dnf install -y util-linux
    elif command_exists yum; then
        yum install -y util-linux
    elif command_exists apk; then
        apk add --no-cache util-linux
    else
        die "不支持的包管理器。请手动安装 util-linux 后重试。"
    fi
}

if ! command_exists mkswap || ! command_exists swapon || ! command_exists findmnt; then
    install_util_linux
fi

command_exists mkswap || die "未找到 mkswap。"
command_exists swapon || die "未找到 swapon。"
command_exists swapoff || die "未找到 swapoff。"
command_exists findmnt || die "未找到 findmnt。"

RAM_MIB=$(awk '/^MemTotal:/ { print int($2 / 1024); exit }' "$MEMINFO")
CURRENT_SWAP_MIB=$(awk 'NR > 1 { total += $3 } END { print int(total / 1024) }' "$PROC_SWAPS")

printf '\n当前状态\n'
printf '  物理内存：%s MiB\n' "$RAM_MIB"
printf '  已启用 Swap：%s MiB\n' "$CURRENT_SWAP_MIB"
if [ "$CURRENT_SWAP_MIB" -gt 0 ]; then
    awk 'NR == 1 { next } { printf "    %s (%d MiB)\n", $1, int($3 / 1024) }' "$PROC_SWAPS"
fi

DEFAULT_FILE=/swapfile
index=2
while [ -e "$DEFAULT_FILE" ] || [ -L "$DEFAULT_FILE" ] || path_in_fstab "$DEFAULT_FILE"; do
    DEFAULT_FILE=/swapfile$index
    index=$((index + 1))
done

while :; do
    printf '\n'
    ask "新 Swap 文件路径 [$DEFAULT_FILE]：" "$DEFAULT_FILE"
    SWAP_FILE=$REPLY

case "$SWAP_FILE" in
        /*) ;;
        *) warn "必须使用绝对路径。"; continue ;;
    esac
    case "$SWAP_FILE" in
        *[[:space:]]*) warn "路径不能包含空白字符。"; continue ;;
    esac
    [ "$SWAP_FILE" != / ] || { warn "不能使用根目录。"; continue; }
    [ ! -e "$SWAP_FILE" ] && [ ! -L "$SWAP_FILE" ] || { warn "$SWAP_FILE 已存在，请换一个路径。"; continue; }
    path_in_fstab "$SWAP_FILE" && { warn "$FSTAB 中已有该路径，请换一个路径。"; continue; }

SWAP_DIR=${SWAP_FILE%/*}
    [ -n "$SWAP_DIR" ] || SWAP_DIR=/
    [ -d "$SWAP_DIR" ] || { warn "目录 $SWAP_DIR 不存在。"; continue; }
    break
done

if [ "$RAM_MIB" -le 2048 ]; then
    DEFAULT_CHOICE=2
else
    DEFAULT_CHOICE=3
fi

while :; do
    printf '\n请选择新增容量：\n'
    printf '  1) 1 GiB\n'
    printf '  2) 2 GiB\n'
    printf '  3) 4 GiB\n'
    printf '  4) 8 GiB\n'
    printf '  5) 自定义（如 1536M、6G）\n'
    ask "选择 [$DEFAULT_CHOICE]：" "$DEFAULT_CHOICE"

case "$REPLY" in
        1) SIZE_MIB=1024 ;;
        2) SIZE_MIB=2048 ;;
        3) SIZE_MIB=4096 ;;
        4) SIZE_MIB=8192 ;;
        5)
            ask "请输入容量：" ""
            custom_size=$(printf '%s' "$REPLY" | tr 'gGmM' 'GGMM')
            case "$custom_size" in
                *G) number=${custom_size%G}; multiplier=1024 ;;
                *M) number=${custom_size%M}; multiplier=1 ;;
                *) number=; multiplier=1 ;;
            esac
            case "$number" in
                ''|*[!0-9]*) warn "格式无效，请输入整数加 M 或 G。"; continue ;;
            esac
            SIZE_MIB=$((number * multiplier))
            ;;
        *) warn "无效选项。"; continue ;;
    esac

[ "$SIZE_MIB" -ge 64 ] || { warn "容量不能小于 64 MiB。"; continue; }
    break
done

FS_TYPE=$(findmnt -n -o FSTYPE -T "$SWAP_DIR" 2>/dev/null || true)
[ -n "$FS_TYPE" ] || die "无法识别 $SWAP_DIR 所在文件系统。"
case "$FS_TYPE" in
    nfs*|cifs|smb*|overlay|tmpfs|fuse*) die "$FS_TYPE 不支持安全创建 swap 文件。" ;;
esac

AVAILABLE_KIB=$(df -Pk "$SWAP_DIR" | awk 'END { print $4 }')
case "$AVAILABLE_KIB" in
    ''|*[!0-9]*) die "无法读取可用磁盘空间。" ;;
esac
REQUIRED_KIB=$((SIZE_MIB * 1024 + 131072))
if [ "$AVAILABLE_KIB" -lt "$REQUIRED_KIB" ]; then
    die "磁盘空间不足：至少需要 $((REQUIRED_KIB / 1024)) MiB，当前可用 $((AVAILABLE_KIB / 1024)) MiB。"
fi

printf '\n即将执行\n'
printf '  系统：%s (%s)\n' "$OS_NAME" "$OS_ID"
printf '  文件：%s\n' "$SWAP_FILE"
printf '  容量：%s MiB\n' "$SIZE_MIB"
printf '  文件系统：%s\n' "$FS_TYPE"
printf '  持久化：写入 %s\n' "$FSTAB"
[ "$FS_TYPE" = btrfs ] && warn "Btrfs 上的 swap 文件不能被快照包含。"
confirm "确认创建？" n || die "已取消，系统未做更改。"

umask 077
if [ "$FS_TYPE" = btrfs ]; then
    if ! command_exists chattr; then
        warn "Btrfs 需要 chattr 来关闭写时复制。"
        confirm "是否现在安装？" y || die "缺少 chattr。"
        if command_exists apt-get; then
            DEBIAN_FRONTEND=noninteractive apt-get install -y e2fsprogs
        elif command_exists dnf; then
            dnf install -y e2fsprogs
        elif command_exists yum; then
            yum install -y e2fsprogs
        elif command_exists apk; then
            apk add --no-cache e2fsprogs-extra
        else
            die "请手动安装 chattr 后重试。"
        fi
    fi
    : >"$SWAP_FILE"
    CREATED=1
    chattr +C "$SWAP_FILE" || die "无法为 Btrfs swap 文件设置 No_COW。"
fi

info "正在分配 $SIZE_MIB MiB 空间..."
if command_exists fallocate && fallocate -l "${SIZE_MIB}M" "$SWAP_FILE"; then
    CREATED=1
else
    warn "fallocate 不可用，改用 dd 分配空间，这可能需要一些时间。"
    rm -f "$SWAP_FILE"
    CREATED=0
    if [ "$FS_TYPE" = btrfs ]; then
        : >"$SWAP_FILE"
        CREATED=1
        chattr +C "$SWAP_FILE" || die "无法为 Btrfs swap 文件设置 No_COW。"
    fi
    dd if=/dev/zero of="$SWAP_FILE" bs=1M count="$SIZE_MIB"
    CREATED=1
fi

chmod 600 "$SWAP_FILE"
command_exists restorecon && restorecon "$SWAP_FILE" >/dev/null 2>&1 || true
mkswap "$SWAP_FILE"
swapon "$SWAP_FILE"
ACTIVE=1
is_active_swap "$SWAP_FILE" || die "swap 启用后未出现在 $PROC_SWAPS 中。"

FSTAB_BACKUP=$(mktemp "${TMPDIR:-/tmp}/add-swap-fstab.XXXXXX")
cp -p "$FSTAB" "$FSTAB_BACKUP"
FSTAB_MODIFIED=1
printf '\n%s none swap sw 0 0\n' "$SWAP_FILE" >>"$FSTAB"

if command_exists systemctl && systemctl is-system-running >/dev/null 2>&1; then
    systemctl daemon-reload || warn "systemd 配置重载失败；重启时仍会读取 $FSTAB。"
fi

DONE=1
rm -f "$FSTAB_BACKUP"
FSTAB_BACKUP=

NEW_TOTAL_MIB=$(awk 'NR > 1 { total += $3 } END { print int(total / 1024) }' "$PROC_SWAPS")
printf '\n完成：%s 已启用并写入 %s。\n' "$SWAP_FILE" "$FSTAB"
printf '当前 Swap 总量：%s MiB\n' "$NEW_TOTAL_MIB"
printf '可用以下命令确认：swapon --show\n'

```