iredmail安裝腳本分析（三）---conf/globalDISTRO值的來源及操作系統(tǒng)的判斷

2024-06-28 14:32:19

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供稿：網(wǎng)友

作者在引入conf/global 文件時(shí)，就已經(jīng)對(duì)操作系統(tǒng)的類型進(jìn)行判斷，同時(shí)也對(duì)DISTRO進(jìn)行了賦值。

部分代碼，如圖：

顯然文件里的KERNEL_NAME的值就是判斷完成的操作系統(tǒng)，具體分析該值是如何得到的。

就是通過命令“uname –s | tr ‘[a-z]’ ‘[A-Z]’得到的，不過作者在此處把小寫換成了大寫。接下來分析根據(jù)不同操作系統(tǒng)，怎么獲得不同的DISTRO值，代碼如下：

if [ X"${KERNEL_NAME}" == X'linux' ]; then    # Directory of RC scripts.    export DIR_RC_SCRIPTS='/etc/init.d'    if [ -f /etc/redhat-release ]; then        # RHEL/CentOS        export DISTRO='RHEL'        # Get distribution version        if grep '/ 6' /etc/redhat-release &>/dev/null; then            # version 6.x            export DISTRO_VERSION='6'        elif grep '/ 7' /etc/redhat-release &>/dev/null; then            # version 7.x            export DISTRO_VERSION='7'        else            export UNSUPPORTED_RELEASE='YES'        fi        # Get distribution name as DISTRO_CODENAME        if grep '^Red' /etc/redhat-release &>/dev/null; then            # RHEL            export DISTRO_CODENAME='rhel'        elif grep '^CentOS' /etc/redhat-release &>/dev/null; then            # CentOS            export DISTRO_CODENAME='centos'        elif grep '^Scientific' /etc/redhat-release &>/dev/null; then            # Scientific Linux            export DISTRO_CODENAME='scientific'        else            export UNSUPPORTED_RELEASE='YES'        fi    elif [ -f /etc/lsb-release ]; then        # Ubuntu        export DISTRO='UBUNTU'        # Ubuntu version number and code name:        #   - 14.04: trusty        #   - 15.04: vivid        export DISTRO_ID="$(grep 'DISTRIB_ID' /etc/lsb-release | awk -F'=' '{PRint $2}')"        export DISTRO_VERSION="$(grep 'DISTRIB_RELEASE' /etc/lsb-release | awk -F'=' '{print $2}')"        export DISTRO_CODENAME="$(grep 'DISTRIB_CODENAME' /etc/lsb-release | awk -F'=' '{print $2}')"        # Unsupported releases: 12.x, 13.x, 14.10        if echo "${DISTRO_VERSION}" | grep -E '^(12|13|14/.10)' &>/dev/null ; then            export UNSUPPORTED_RELEASE='YES'        fi    elif [ -f /etc/debian_version ]; then        # Debian        export DISTRO='DEBIAN'        # Get major release version number        export DISTRO_VERSION="$(cat /etc/debian_version)"        # Set distro code name and unsupported releases.        if grep '^7' /etc/debian_version &>/dev/null || /            grep -i '^wheezy' /etc/debian_version &>/dev/null; then            export DISTRO_VERSION='7'            export DISTRO_CODENAME='wheezy'        elif grep '^8' /etc/debian_version &>/dev/null || /            grep -i '^jessie' /etc/debian_version &>/dev/null; then            export DISTRO_VERSION='8'            export DISTRO_CODENAME='jessie'        else            export UNSUPPORTED_RELEASE='YES'        fi        # Override settings.        export SHELL_NOLOGIN='/usr/sbin/nologin'    else        export UNSUPPORTED_RELEASE='YES'    fielif [ X"${KERNEL_NAME}" == X'FREEBSD' ]; then    export DISTRO='FREEBSD'    export DISTRO_VERSION="$(uname -r |awk -F'[.-]' '{print $1}')"    # Directory of RC scripts.    export DIR_RC_SCRIPTS='/usr/local/etc/rc.d'    export PYTHON_BIN='/usr/local/bin/python'    # Unsupported releases: 7, 8.    if echo "${DISTRO_VERSION}" | grep '^[78]' &>/dev/null ; then        export UNSUPPORTED_RELEASE='YES'    fi    export SHELL_BASH='/usr/local/bin/bash'    # Default passWord scheme.    export DEFAULT_PASSWORD_SCHEME='BCRYPT'elif [ X"${KERNEL_NAME}" == X'OPENBSD' ]; then    export DISTRO='OPENBSD'    export DISTRO_VERSION="$(uname -r)"    # Directory of RC scripts.    export DIR_RC_SCRIPTS='/etc/rc.d'    export RC_CONF_LOCAL='/etc/rc.conf.local'    export SHELL_BASH='/usr/local/bin/bash'    export PYTHON_BIN='/usr/local/bin/python'    # Unsupported release: 5.6 and earlier versions.    if echo "${DISTRO_VERSION}" | grep '^5.[123456]' &>/dev/null ; then        export UNSUPPORTED_RELEASE='YES'    fi    # Default password scheme.    export DEFAULT_PASSWORD_SCHEME='BCRYPT'else    # Not support *BSD and other distrobutions yet.    echo "Error: Your OS is not supported yet."    exit 255fi

代碼比較長(zhǎng)，不過脈絡(luò)比較清晰，首先根據(jù)KERNEL_NAME的值判斷是哪種操作系統(tǒng)，作者給出的判斷是3種，分別是LINUX OPENBSD FREEBSD , 也就是該腳本只能在這3種平臺(tái)上進(jìn)行部署，如果需要自己擴(kuò)展的話，就可以在增加新的判斷，最后如果3種都不是的話，就直接返回255，如下代碼:

echo "Error: Your OS is not supported yet."exit 255

接下來分析當(dāng)KERNEL_NAME的值為L(zhǎng)INUX，腳本做了什么，首先定義了一個(gè)變量

export DIR_RC_SCRIPTS='/etc/init.d'

linux中一般啟動(dòng)腳本都是放在這個(gè)目錄里的,LINUX本身也有很多版本，因此作者在此處又進(jìn)行多種類型的判斷，判斷的依據(jù)文件分別是/etc/redhat-release /etc/lsb-release /etc/debian_version這3種文件分別對(duì)應(yīng)rhel/centos ubuntu debian , 從而也說明在LINUX的版本中，只支持這3種，其他的LINUX版本是不支持的，最后作者返回一句代碼：

定義了一個(gè)UNSUPPORTED_RELEASE變量，在后續(xù)的代碼應(yīng)該會(huì)調(diào)用這個(gè)變量來判斷是否支持。

針對(duì)這3種LINUX，作者又具體細(xì)分到不同的小版本中，首先看rhel/centos 系列，下面代碼：

首先根據(jù)存在redhat-release文件，定義了DISTRO的值

if [ -f /etc/redhat-release ]; then

export DISTRO='RHEL'

這樣在get_all.sh的腳本里調(diào)用時(shí)就有了判斷依據(jù)，接著判斷具體的版本，

if grep '/ 6' /etc/redhat-release &>/dev/null; then            # version 6.x            export DISTRO_VERSION='6'        elif grep '/ 7' /etc/redhat-release &>/dev/null; then            # version 7.x            export DISTRO_VERSION='7'        else            export UNSUPPORTED_RELEASE='YES'        fi

顯然只支持6和7兩個(gè)版本，也就是安裝時(shí)，如果不是這2個(gè)版本的話，就會(huì)返回unsupport_release的值為YES了。

rhel還有兩個(gè)個(gè)反編譯版本即centos ，Scientific Linux, 因此作者又定義了一個(gè)變量來區(qū)別 DISTRO_CODENAME, 代碼如下:

if grep '^Red' /etc/redhat-release &>/dev/null; then            # RHEL            export DISTRO_CODENAME='rhel'        elif grep '^CentOS' /etc/redhat-release &>/dev/null; then            # CentOS            export DISTRO_CODENAME='centos'        elif grep '^Scientific' /etc/redhat-release &>/dev/null; then            # Scientific Linux            export DISTRO_CODENAME='scientific'        else            export UNSUPPORTED_RELEASE='YES'        fi

顯然在/etc/redhat-release文件里，不同的發(fā)行版本有不同的關(guān)鍵字，這樣關(guān)于紅帽系的操作系統(tǒng)，作者就已經(jīng)區(qū)分完畢了。

接下來關(guān)于ubuntu的判斷就簡(jiǎn)單多了，看圖

根據(jù)/etc/lsb-release的文件是否存在，賦值DISTRO為UBUNTU，然后判斷具體版本，看代碼

        export DISTRO_ID="$(grep 'DISTRIB_ID' /etc/lsb-release | awk -F'=' '{print $2}')"        export DISTRO_VERSION="$(grep 'DISTRIB_RELEASE' /etc/lsb-release | awk -F'=' '{print $2}')"        export DISTRO_CODENAME="$(grep 'DISTRIB_CODENAME' /etc/lsb-release | awk -F'=' '{print $2}')"        # Unsupported releases: 12.x, 13.x, 14.10        if echo "${DISTRO_VERSION}" | grep -E '^(12|13|14/.10)' &>/dev/null ; then            export UNSUPPORTED_RELEASE='YES'        fi

從程序可以看出UBUNTU的ID , RELEASE , CODENAME的值都在/etc/lsb-release的文件里，用grep 和awk匹配后，賦予不同變量的值。

用grep 篩選出系統(tǒng)版本為12,13,14.10的都為不支持版本，目前支持的版本為14.04,15.04

接下來判斷的就是DEBIAN了，同樣是判斷文件，如圖：

文件存在，則DISTRO的值為DEBIAN，接下來判斷版本號(hào)：

# Get major release version number        export DISTRO_VERSION="$(cat /etc/debian_version)"

cat /etc/debian_version 一個(gè)命令就可以得到具體版本，比rhel更容易判斷

接下來對(duì)具體版本進(jìn)行判斷，見代碼：

# Set distro code name and unsupported releases.        if grep '^7' /etc/debian_version &>/dev/null || /            grep -i '^wheezy' /etc/debian_version &>/dev/null; then            export DISTRO_VERSION='7'            export DISTRO_CODENAME='wheezy'        elif grep '^8' /etc/debian_version &>/dev/null || /            grep -i '^jessie' /etc/debian_version &>/dev/null; then            export DISTRO_VERSION='8'            export DISTRO_CODENAME='jessie'        else            export UNSUPPORTED_RELEASE='YES'        fi