计算机专业英语（第二版）孙建忠电子教案 Chapter5.ppt

Computer English Chapter 5 Operating System 5.2 FreeBSD vs. Linux vs. Windows 2000 Windows is adequate for routine desktop apps, but it is unable to handle heavy network loads. A few organizations try to make it work as an Internet server. For instance, uses Windows-NT, as can be verifyed by the error messages that their webserver produces, such as this recent example: Error Message: [Microsoft][ODBC SQL Server Driver][SQL Server]Cant allocate space for object queryHistory in database web because the default segment is full. For their own Hotmail Internet servers, Microsoft used FreeBSD for many years. Windows系统可以满足日常的桌面应用，但是无法处理网络重负载。很少有机构尝试让它作为Internet 服务器来运行，例如网站使用Windows-NT系统，但是WEB服务器经常产生如下的错误信息，错误消息：[Microsoft][ODBC SQL Server Driver][SQL Server]不能在数据库web中为对象queryHistory分配空间，因为default字段已满。）微软公司自己的Hotmail服务器使用FreeBSD系统已经很多年了。 5.2 FreeBSD vs. Linux vs. Windows 2000 Security FreeBSD has been the subject of a massive auditing project for several years. All of the critical system components have been checked and rechecked for security-related errors. The entire system is open source so the security of the system can and has been verified by third parties. A default FreeBSD installation has yet to be affected by a single CERT security advisory in 2000. 安全性 FreeBSD 系统的安全性已经作为一个课题被大量的研究，所有的可能会导致问题的系统成分都被再三的检验以发现与安全相关的错误。由于整个系统是开放的，所以安全性可以被第三方所检验。FreeBSD的默认安装毫无疑问受CERT 2000年的安全报告影响。 5.2 FreeBSD vs. Linux vs. Windows 2000 FreeBSD also has the notion of kernel security levels. These are much more powerful than simple run-levels since they allow the administrator to completely deny access to certain operating system functions such as reading /dev/mem, changing file system flags, or writing to disks without mounting a file system. FreeBSD includes a very robust packet filtering firewall system and many intrusion detection tools. FreeBSD系统内核分为不同的安全等级，这比单级运行的内核更强大，因为它允许超级用户完全拒绝一些系统操作，像读磁盘/内存，改变文件系统标志，在没有挂接文件系统时对磁盘进行写操作。FreeBSD系统包含了非常健壮的包过滤防火墙系统和许多非法入侵检测工具。 5.2 FreeBSD v