linux 报错：Permission denied——如何切换到 root 身份

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在Linux环境中，非root用户执行`fdisk -l`会遇到权限问题。解决方法是切换到root权限，如使用`sudo su`。成功切换后，可以查看所有磁盘信息，包括新添加的硬盘。对于新硬盘的分区，需要进一步进行分区操作，如创建主分区或逻辑分区，并格式化为合适的文件系统。

文章目录

1. 问题：在一般用户身份下使用`fdisk -l`遭到拒绝：`Permission denied`
2. 解决：切换到 root 身份
3. 接下来的问题：如何给新添加的硬盘重新分区

1. 问题：在一般用户身份下使用`fdisk -l`遭到拒绝：`Permission denied`

suer@suer-virtual-machine:~$ fdisk -l
fdisk: cannot open /dev/ram0: Permission denied
fdisk: cannot open /dev/ram1: Permission denied
fdisk: cannot open /dev/ram2: Permission denied
fdisk: cannot open /dev/ram3: Permission denied
fdisk: cannot open /dev/ram4: Permission denied
fdisk: cannot open /dev/ram5: Permission denied
fdisk: cannot open /dev/ram6: Permission denied
fdisk: cannot open /dev/ram7: Permission denied
fdisk: cannot open /dev/ram8: Permission denied
fdisk: cannot open /dev/ram9: Permission denied
fdisk: cannot open /dev/ram10: Permission denied
fdisk: cannot open /dev/ram11: Permission denied
fdisk: cannot open /dev/ram12: Permission denied
fdisk: cannot open /dev/ram13: Permission denied
fdisk: cannot open /dev/ram14: Permission denied
fdisk: cannot open /dev/ram15: Permission denied
fdisk: cannot open /dev/fd0: Permission denied
fdisk: cannot open /dev/sda: Permission denied
fdisk: cannot open /dev/sdb: Permission denied

2. 解决：切换到 root 身份

有以下三种方式切换到 root 身份：

方法1：输入su，然后按照提示输入相应的root密码，就可登录到root权限下。

方法2：输入sudo su，然后按照提示输入相应的root密码，就可登录到root权限下(这个命令下，一般不需要输入相应的root密码)。

方法3：输入su root，然后按照提示输入相应的root密码，就可登录到root权限下。

附：su用来在用户间切换，也可以是从root身份切换到普通用户：su - (用户名)
（注意： - 两边都有空格）

su = switch user 切换用户（默认切换成root用户），不切换工作环境
但是直接使用su给用户的权限太大，增加了风险，为了限制用户的权限出现了sudo
sudo = superuser do （ /etc/sudoers ）
一般的使用情况下，最好使用sudo来执行命令，避免自己误操作破坏了系统。
如果是存在多用户使用同一个系统的话，主用户可以使用root权限来配置 /etc/sudoers 文件来指派不同用户不同的权限，从而保证系统的安全。

使用方法二的代码sudo su成功：

suer@suer-virtual-machine:~$ sudo su
root@suer-virtual-machine:/home/suer# fdisk -lu

root@suer-virtual-machine:/home/suer# fdisk -lu
Disk /dev/ram0: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram1: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram2: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram3: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram4: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram5: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram6: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram7: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram8: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram9: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram10: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram11: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram12: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram13: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram14: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/ram15: 64 MiB, 67108864 bytes, 131072 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes






Disk /dev/sda: 100 GiB, 107374182400 bytes, 209715200 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x7aeec698

Device     Boot    Start      End  Sectors Size Id Type
/dev/sda1  *        2048 67108863 67106816  32G 83 Linux
/dev/sda2       67110910 83884031 16773122   8G  5 Extended
/dev/sda5       67110912 83884031 16773120   8G 82 Linux swap / Solaris


Disk /dev/sdb: 50 GiB, 53687091200 bytes, 104857600 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes