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[操作系统]iredmail安装脚本分析(三)


作者在引入conf/global 文件时,就已经对操作系统的类型进行判断,同时也对DISTRO进行了赋值。

部分代码,如图:

image

显然文件里的KERNEL_NAME的值就是判断完成的操作系统,具体分析该值是如何得到的。

image

就是通过命令“uname –s  | tr ‘[a-z]’ ‘[A-Z]’得到的,不过作者在此处把小写换成了大写。 接下来分析根据不同操作系统,怎么获得不同的DISTRO值,代码如下:

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

代码比较长,不过脉络比较清晰,首先根据KERNEL_NAME的值判断是哪种操作系统,作者给出的判断是3种,分别是LINUX   OPENBSD   FREEBSD  , 也就是该脚本只能在这3种平台上进行部署,如果需要自己扩展的话,就可以在增加新的判断,最后如果3种都不是的话,就直接返回255,如下代码:

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

接下来分析当KERNEL_NAME的值为LINUX,脚本做了什么,首先定义了一个变量

export DIR_RC_SCRIPTS='/etc/init.d'

linux中一般启动脚本都是放在这个目录里的,LINUX本身也有很多版本,因此作者在此处又进行多种类型的判断,判断的依据文件分别是/etc/redhat-release  /etc/lsb-release  /etc/debian_version这3种文件分别对应rhel/centos  ubuntu  debian  , 从而也说明在LINUX的版本中,只支持这3种,其他的LINUX版本是不支持的,最后作者返回一句代码:

image

定义了一个UNSUPPORTED_RELEASE变量,在后续的代码应该会调用这个变量来判断是否支持。

针对这3种LINUX,作者又具体细分到不同的小版本中,首先看rhel/centos 系列,下面代码:

首先根据存在redhat-release文件,定义了DISTRO的值

if [ -f /etc/redhat-release ]; then
export DISTRO='RHEL'

这样在get_all.sh的脚本里调用时就有了判断依据,接着判断具体的版本,

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

显然只支持6和7两个版本,也就是安装时,如果不是这2个版本的话,就会返回unsupport_release的值为YES了。

rhel还有两个个反编译版本即centos ,Scientific Linux,    因此作者又定义了一个变量来区别 DISTRO_CODENAME, 代码如下:

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

显然在/etc/redhat-release文件里,不同的发行版本有不同的关键字,这样关于红帽系的操作系统,作者就已经区分完毕了。


接下来关于ubuntu的判断就简单多了,看图

image

根据/etc/lsb-release的文件是否存在,赋值DISTRO为UBUNTU,然后判断具体版本,看代码

    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

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

用grep 筛选出系统版本为12,13,14.10的都为不支持版本,目前支持的版本为14.04,15.04


接下来判断的就是DEBIAN了,同样是判断文件,如图:

image

文件存在,则DISTRO的值为DEBIAN,接下来判断版本号:

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

cat /etc/debian_version  一个命令就可以得到具体版本,比rhel更容易判断

接下来对具体版本进行判断,见代码:

# 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

显然只支持DEBIAN的7,8两个版本,到此DISTRO的值和操作系统的判断结束,如果想新增特殊操作系统的话或者自己定义的话,在此处加入自己的代码即可。