sudo 命令无法使用

1. 不能使用sudo命令解决方法:
想查看这个用户可以使用哪些sudo命令，输入正确密码却不能查看，原因就是在/etc/sudoers中未添加该用户。

[xm@oracle ~]$ sudo -l
[sudo] password for xm: 
Sorry, user xm may not run sudo on oracle.

2.解决方法(添加用户至sudoers文件):

(1) 切换root用户

[xm@oracle ~]$ su - root
Password: 
[root@oracle ~]#

(2) 添加用户至 sudoers 文件(vim /etc/sudoers 或者 visudo)

[root@oracle ~]# visudo
## Sudoers allows particular users to run various commands as
## the root user, without needing the root password.
##
## Examples are provided at the bottom of the file for collections
## of related commands, which can then be delegated out to particular
## users or groups.
##
## This file must be edited with the 'visudo' command.

## Host Aliases
## Groups of machines. You may prefer to use hostnames (perhaps using
## wildcards for entire domains) or IP addresses instead.
# Host_Alias     FILESERVERS = fs1, fs2
# Host_Alias     MAILSERVERS = smtp, smtp2

## User Aliases
## These aren't often necessary, as you can use regular groups
## (ie, from files, LDAP, NIS, etc) in this file - just use %groupname
## rather than USERALIAS
# User_Alias ADMINS = jsmith, mikem

在93行的位置添加该用户，正常退出即可

     90 ## Allow root to run any commands anywhere
     91 root    ALL=(ALL)       ALL
     92 xh      ALL=(ALL)       ALL
     93 xm      ALL=(ALL)       ALL
     94 ## Allows members of the 'sys' group to run networking, software,
     95 ## service management apps and more.
     96 # %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES,         LOCATE, DRIVERS

(3) 正常使用sudo命令

[root@oracle ~]# su - xm
[xm@oracle ~]$ sudo -l
[sudo] password for xm: 
Matching Defaults entries for xm on this host:
    !visiblepw, always_set_home, env_reset, env_keep="COLORS DISPLAY HOSTNAME
    HISTSIZE INPUTRC KDEDIR LS_COLORS", env_keep+="MAIL PS1 PS2 QTDIR USERNAME LANG
    LC_ADDRESS LC_CTYPE", env_keep+="LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT
    LC_MESSAGES", env_keep+="LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE",
    env_keep+="LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY",
    secure_path=/sbin\:/bin\:/usr/sbin\:/usr/bin

User xm may run the following commands on this host:
    (ALL) ALL

由结果看出：可以执行的sudo命令为所有ALL