随笔分类 -  LINUX/UNIX

摘要：1.passwd命令 2.chage -l命令 Showing Password Expiry Information with chage -l 如果时间小于（Minimum number of days between password change : 3），则不允许修改密码。 阅读全文

摘要：Configuration Files for User Management Defaults When working with tools as useradd, some default values are assumed. These default values are set in 阅读全文

摘要：Modifying the Configuration Files To add user accounts, it suffices that one line is added to /etc/passwd and another line is added to /etc/shadow, in 阅读全文

摘要：sudo Instead of using the root user account, unprivileged users can be configured for using administrator permissions on specific tasks by using sudo. 阅读全文

摘要：Using su The su command allows users to open a terminal window, and from that terminal start a sub shell in which the user has another identity. To perform administrative tasks, for insta... 阅读全文

摘要：ls Common Command-Line Options Command Use： ls -l Shows a long listing, which includes information about file properties, such as creation date and permissions. ls -a Shows all fil... 阅读全文

摘要：Counting Lines, Words, and Characters with wc When working with text files, you sometimes get a large amount of output. Before deciding which approach 阅读全文

摘要：Sorting File Contents and Output with sort Another very useful command to use on text file is sort . As you can probably guess, this command sorts tex 阅读全文

摘要：Filtering Specific Columns with cut When working with text files, it can be useful to filter out specific fields. Imagine that you need to see a list 阅读全文

摘要：[root@rhel7 ~]# cat rusky --cat命令查看文件内容 line1 line2 line3 line4 line5 line6 line7 line8 line9 line10 [root@rhel7 ~]# tail -n 3 rusky --查看最后3行内容 line8 line9 line10 [root@rhel7 ~]# tail -3 rusky ... 阅读全文

摘要：[rusky@rhel7 test]$ lstest1 test123 test2 test317 test33 test335 test336 test44 testtest[rusky@rhel7 test]$ ls test?3test33[rusky@rhel7 test]$ ls test??3test123[rusky@rhel7 test]$ ls test... 阅读全文

摘要：■ The mount command gives an overview of all mounted devices. To get this information, the /proc/mounts file is read, where the kernel keeps informati 阅读全文

摘要：/etc/motd and /etc/issue Bash offers an option to include messages in the /etc/motd and the /etc/issue files. Messages in /etc/motd display after a us 阅读全文

摘要：Environment Configuration Files When a user logs in, an environment is created for that user automatically. This happens based on four different files 阅读全文

摘要：普通用户登录系统报错，提示： -bash: ulimit: open files: cannot modify limit: Operation not permitted. 处理方法： #vi /etc/ssh/sshd_config --使用root账号修改UseLoin 为yes UseLog 阅读全文

摘要：对所有用户都生效： vi /etc/profile 添加一行如下： ulimit -n 65535 执行source /etc/profile生效，不需要重启服务器。 $ source /etc/profile$ ulimit -n65535 以后重启服务器后也生效。 如果不修改，默认值为1024， 阅读全文

摘要：/dev/null 文件 如果希望执行某个命令，但又不希望在屏幕上显示输出结果，那么可以将输出重定向到 /dev/null： /dev/null 是一个特殊的文件，写入到它的内容都会被丢弃；如果尝试从该文件读取内容，那么什么也读不到。但是 /dev/null 文件非常有用，将命令的输出重定向到它，会 阅读全文

摘要：定时执行命令： 定时执行脚本： at命令的常见用法： at 2pm + 2 days /root/test.sh //2天后，下午2点执行test.sh脚本 at 10am + 2 weeks /root/test.sh //2个星期后，早上10点执行test.sh脚本 at 12am tomorr 阅读全文

摘要：简单测试例子： 添加定时任务前，注意查看crond服务是否已经启动，如果未启动，则用命令service crond start命令启动。 注意给脚本添加可执行权限。 测试2： 多个数值用逗号隔开，如在每月1、3、4、12号的22:03执行定时任务 测试3： 连续时间可用“-”表示。如在每个小时10分 阅读全文

摘要：目标环境，5台linux centos 6.3， 一台作为NTPD服务与外部公共NTP服务同步时间，同时作为内网的NTPD服务器，其他机器与这台服务做时间同步。 1、负责与外部公共NTPD服务同步标准时间 2、作为内外网络的NTPD服务 NTPD服务平滑同步 1、NTP时间同步方式选择 NTP同步方 阅读全文