linuxsudoi

A. linux里面root登录和sudo -i区别是什么

root用户表示直接拥有最大权，可以不加任何条件执行任何操作，从便利程度上来说是很便利的；
sudo -i：为了频繁的执行某些只有超级用户才能执行的权限，而不用每次输入密码，可以使用该命令；提示输入密码时该密码为当前账户的密码，没有时间限制，执行该命令后提示符变为“#”而不是“$”，想退回普通账户时可以执行“exit”或“logout” ；
从安全层面上来说，直接使用root是很不安全的，不小心就会被 "rm -rf", 反而，使用sudo -i ，这样更安全一些,至少不能直接使用命令删除一些重要的文件和进程等；

B. linux下面的sudo命令什么意思

sudo 表示 “superuser do”。 它允许已验证的用户以其他用户的身份来运行命令。其他用户可版以是普通权用户或者超级用户。然而，大部分时候我们用它来以提升的权限来运行命令。

apt 是Linux下的一款安装包管理工具，是一个客户/服务器系统。sudo apt-get是用来安装linux下的各种工具包的。

(2)linuxsudoi扩展阅读：

注意事项：

编辑sudo的配置文件/etc/sudoers是一般不要直接使用vi（vi /etc/sudoers）去编辑，因为sudoers配置有一定的语法，直接用vi编辑保存系统不会检查语法，如有错也保存了可能导致无法使用sudo工具，而使用visudo命令去配置保存时会进行语法检查，有错会有提示。

命令一定要使用绝对路径，避免其他目录的同名命令被执行，造成安全隐患 ，因此使用的时候也是使用绝对路径！

C. 在linux操作系统中怎样读取u盘

1、首先需要把U盘插入Linux电脑，确保U盘指示灯是亮着的进入Linux系统主界面，按Ctrl+Alt+T打开命令窗口。

D. sudo -i和sudo -s有什么区别

sudo -i：

Linux终端命令下改变用户对命令使用权限的命令。
sudo-s ：

执行环境变数中的 SHELL 所指定的 shell ，或是 /etc/passwd 里所指定的 shell 。

E. Linux下的命令sudo怎么读

类似拼音的的读法：su do或者xiu do，这样的读法，详细单词是superuserdo，意为超级管理员可以做的动作。

F. 在linux操作系统中怎样读取u盘为啥我的linux操作系

1、首先需要把U盘插入Linux电脑，确保U盘指示灯是亮着的进入Linux系统主界面，按Ctrl+Alt+T打开命令窗口。

2、先获取高级用户权限，输入命令:sudo -i，确定后输入高级用户密码。

3、首先使用fdisk -l命令查看一下U盘是否有被识别到，及识别的U盘是在哪个位置，本次接入看到U盘的位置是/dev/Sdb4。

4、输入挂载U盘命令：mount /dev/sdb4 /mnt，回车后即挂载U盘成功。

5、继续输入：cd 回车，可以查看U盘下的文件。

利用WinPE工具可以通过U盘来安装Linux系统，下面以U盘WinPE工具安装Centos6.4版Linux为例，方法如下：
1.在U盘上安装好WinPE（可以选择老毛桃U盘工具、大白菜PE等）
2.在U盘根目录建立一个名为LMT的目录，将CentOS-6.4-x86_64-minimal.iso镜像拷入U盘下的LMT目录。
3.将U盘插入电脑。重启电脑，进入BIOS选择U盘启动，F10保存退出。
4.系统从U盘启动以后显示出老毛桃的启动菜单。
5.菜单中有一项“启动自定义ISO/IMG文件（LMT目录）”，选择该项。

6.系统会列出LMT目录中的ISO文件，直接输入对应的序号就可以安装了。

首先，你的linux具体是什么发行版？还有，你的u盘使用什么格式？再有，你有没有执行mount挂载？这些都有可能会影响u盘的显示。
早期的linux，特别是红帽企业版的第4版，第5版(RedHat Enterprise Linux 4、RedHat Enterprise Linux 5，通常习惯缩写RHEL4、RHEL5)，不仅要执行mount -t 命令才能挂载。而且对于NTFS格式的磁盘，还要编译安装ntfs-3g。而对于linux本身支持的ext2,ext3以及windows下比较传统的fat32则默认支持。当时的centos，fedora等基于红帽的linux也是如此。
现在的一些发行版，特别是主要面对桌面用户的，例如ubuntu，fedora，往往是在安装完系统后，就能识别各种类型的磁盘分区的。不论它是fat32还是ntfs。当然了，linux的ext2、ext3、ext4、xfs肯定也是支持的。但是一些主要是面对服务的，例如RHEL6、RHEL7、CentOS6、CentOS7等等，往往默认的安装系统时，就没有安装关于识别NTFS的软件包。需要用户自己去安装。但是这个安装已经比较方便了。前面说的RHEL4、RHEL5的时代，ntfs-3g只能用编译安装。而现在RHEL或CentOS6或7的时代，ntfs-3g已经有了rpm包，并添加进了yum软件源里面了，这意味着安装它已经不想以前那么麻烦了。
]$ yum list | grep ntfs
ntfs-3g.x86_64 2:2016.2.22-3.el6 @epel
ntfs-3g.i686 2:2016.2.22-3.el6 epel
ntfs-3g-devel.i686 2:2016.2.22-3.el6 epel
ntfs-3g-devel.x86_64 2:2016.2.22-3.el6 epel
ntfsprogs.i686 2.0.0-13.el6 epel
ntfsprogs.x86_64 2:2016.2.22-3.el6 epel
ntfsprogs-devel.i686 2.0.0-13.el6 epel
ntfsprogs-devel.x86_64 2.0.0-13.el6 epel
ntfsprogs-gnomevfs.x86_64 2.0.0-13.el6 epel

从这些可以看出，只要用户配置好了epel源，就能装ntfs-3g。装好了，那么使用ntfs格式的磁盘，分区等就能识别了。

此外，现在的linux版本中各种格式的分区，只要能识别就能自动挂载。属于即插即用了。

G. 如何手动释放Linux内存的方法

1、首先打开Linux命令窗口，可使用快捷键Ctrl+Alt+T打开。

H. linux系统如何把u盘中的文件复制过来

linux系统要把u盘中的文件复制过来需要先把U盘挂载到系统中的某一个位置，然后版再使用cp命令完权成拷贝。可以参考以下操作步骤：

1、把U盘插入Linux电脑，确保U盘指示灯是亮着的。进入Linux系统主界面，按Ctrl+Alt+T打开命令窗口，先获取高级用户权限，输入命令:sudo -i，确定后输入高级用户密码

I. Linux操作系统下Sudo命令的使用方法

建议：
在Linux系统下，右键打开终端后，可以输入"man sudo"或者"info sudo"查询，因为使用方法实在是太多，可以摘要如下，其他可以自己查看。
NAME
sudo, sudoedit - execute a command as another user

SYNOPSIS
sudo -h | -K | -k | -L | -l | -V | -v

sudo [-bEHPS] [-p prompt] [-u username|#uid] [VAR=value]
{-i | -s | command}

sudoedit [-S] [-p prompt] [-u username|#uid] file ...

OPTIONS
sudo accepts the following command line options:

-b The -b (background) option tells sudo to run the given command in
the background. Note that if you use the -b option you cannot use
shell job control to manipulate the process.

-E The -E (preserve environment) option will override the env_reset
option in sudoers(5)). It is only available when either the
matching command has the SETENV tag or the setenv option is set in
sudoers(5).

-e The -e (edit) option indicates that, instead of running a command,
the user wishes to edit one or more files. In lieu of a command,
the string "sudoedit" is used when consulting the sudoers file. If
the user is authorized by sudoers the following steps are taken:

1. Temporary copies are made of the files to be edited with the
owner set to the invoking user.

2. The editor specified by the VISUAL or EDITOR environment vari-
ables is run to edit the temporary files. If neither VISUAL
nor EDITOR are set, the program listed in the editor sudoers
variable is used.

3. If they have been modified, the temporary files are copied back
to their original location and the temporary versions are
removed.

If the specified file does not exist, it will be created. Note
that unlike most commands run by sudo, the editor is run with the
invoking user's environment unmodified. If, for some reason, sudo
is unable to update a file with its edited version, the user will
receive a warning and the edited will remain in a temporary
file.

-H The -H (HOME) option sets the HOME environment variable to the
homedir of the target user (root by default) as specified in
passwd(5). By default, sudo does not modify HOME (see set_home and
always_set_home in sudoers(5)).

-h The -h (help) option causes sudo to print a usage message and exit.

-i The -i (simulate initial login) option runs the shell specified in
the passwd(5) entry of the user that the command is being run as.
The command name argument given to the shell begins with a '-' to
tell the shell to run as a login shell. sudo attempts to change to
that user's home directory before running the shell. It also ini-
tializes the environment, leaving TERM unchanged, setting HOME,
SHELL, USER, LOGNAME, and PATH, and unsetting all other environment
variables. Note that because the shell to use is determined before
the sudoers file is parsed, a runas_default setting in sudoers will
specify the user to run the shell as but will not affect which
shell is actually run.

-K The -K (sure kill) option is like -k except that it removes the
user's timestamp entirely. Like -k, this option does not require a
password.

-k The -k (kill) option to sudo invalidates the user's timestamp by
setting the time on it to the Epoch. The next time sudo is run a
password will be required. This option does not require a password
and was added to allow a user to revoke sudo permissions from a
.logout file.

-L The -L (list defaults) option will list out the parameters that may
be set in a Defaults line along with a short description for each.
This option is useful in conjunction with grep(1).

-l The -l (list) option will list out the allowed (and forbidden) com-
mands for the invoking user on the current host.

-P The -P (preserve group vector) option causes sudo to preserve the
invoking user's group vector unaltered. By default, sudo will ini-
tialize the group vector to the list of groups the target user is
in. The real and effective group IDs, however, are still set to
match the target user.

-p The -p (prompt) option allows you to override the default password
prompt and use a custom one. The following percent ('%') escapes
are supported:

%H expanded to the local hostname including the domain name (on if
the machine's hostname is fully qualified or the fqdn sudoers
option is set)

%h expanded to the local hostname without the domain name

%p expanded to the user whose password is being asked for
(respects the rootpw, targetpw and runaspw flags in sudoers)

%U expanded to the login name of the user the command will be run
as (defaults to root)

%u expanded to the invoking user's login name

%% two consecutive % characters are collapsed into a single %
character

-S The -S (stdin) option causes sudo to read the password from the
standard input instead of the terminal device.

-s The -s (shell) option runs the shell specified by the SHELL envi-
ronment variable if it is set or the shell as specified in
passwd(5).

-u The -u (user) option causes sudo to run the specified command as a
user other than root. To specify a uid instead of a username, use
#uid. When running commands as a uid, many shells require that the
'#' be escaped with a backslash ('\'). Note that if the targetpw
Defaults option is set (see sudoers(5)) it is not possible to run
commands with a uid not listed in the password database.
-V The -V (version) option causes sudo to print the version number and
exit. If the invoking user is already root the -V option will
print out a list of the defaults sudo was compiled with as well as
the machine's local network addresses.

-v If given the -v (validate) option, sudo will update the user's
timestamp, prompting for the user's password if necessary. This
extends the sudo timeout for another 5 minutes (or whatever the
timeout is set to in sudoers) but does not run a command.

-- The -- flag indicates that sudo should stop processing command line
arguments. It is most useful in conjunction with the -s flag.

Environment variables to be set for the command may also be passed on
the command line in the form of VAR=value, e.g.
LD_LIBRARY_PATH=/usr/local/pkg/lib. Variables passed on the command
line are subject to the same restrictions as normal environment vari-
ables with one important exception. If the setenv option is set in
sudoers, the command to be run has the SETENV tag set or the command
matched is ALL, the user may set variables that would overwise be for-
bidden. See sudoers(5) for more information.

J. Linux里面sudo -i命令作用是什么

显示当前使用这个命令的账户拥有的权限