Linux 使用 VLC 多媒体的正确姿势，解决 VLC is not supposed to be run as root. 的问题

Posted 2021-10-22 ～晨曦静竹～

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How to run vlc video player as root user in Linux

首先是安装，不过在Debian系Linux中，使用 apt / apt-get 包管理会很轻松：

	$ sudo apt install vlc -y

出现 vlc 多媒体图标 。

若读者是Red Hat系Linux，则可参考博主另一篇：yum 安装 VLC多媒体

可能细心的小伙伴们，在安装后就已经发现了，无论什么系Linux，但当我们在root账户下直接运行VLC时，就会出下如下报错：

	VLC is not supposed to be run as root. Sorry.
	If you need to use real-time priorities and/or privileged TCP ports
	you can use vlc-wrapper (make sure it is Set-UID root and
	cannot be run by non-trusted users first).

别着急，博主这就为你解答，执行如下命令：

①：

	cp /usr/bin/vlc /usr/bin/vlc-backup

②：

	needle=$(objdump -d /usr/bin/vlc | grep euid | tail -1 | awk '{print "\\\\x"$2"\\\\x"$3"\\\\x"$4"\\\\x"$5"\\\\x"$6;}')

③：

	sed -ir "s/$needle/\\xb8\\x01\\x00\\x00\\x00/" /usr/bin/vlc

此时，会发现在 root 权限下可正常运行 vlc多媒体了。

或许，会有小伙伴发问，是如何解决该问题的？博主，也为感兴趣的读者转载了国外大佬解决该问题的全过程：

How I found this out

When starting vlc as root you will probably get the following error message:

	VLC is not supposed to be run as root. Sorry.
	If you need to use real-time priorities and/or privileged TCP ports
	you can use vlc-wrapper (make sure it is Set-UID root and
	cannot be run by non-trusted users first).

Here is how I change this behavior:

	gdb /usr/bin/vlc
	(gdb) info functions
	All defined functions:

	Non-debugging symbols:
	[...]
	0x0000000000400f40  geteuid
	[...]

Let’s break in the function to get the effective user identity:

	(gdb) break geteuid
	Breakpoint 1 at 0x400f40

Let’s start the program to run till the first breakpoint:

	(gdb) run
	Starting program: /usr/bin/vlc 

	Breakpoint 1, 0x00007ffff71cfc70 in geteuid () from /lib64/libc.so.6

OK, let’s trace the program one command at a time:

	(gdb) stepi
	0x00007ffff71cfc75 in geteuid () from /lib64/libc.so.6
	(gdb) stepi
	0x00007ffff71cfc77 in geteuid () from /lib64/libc.so.6
	(gdb) 
	0x0000000000401103 in ?? ()
	(gdb) 
	0x0000000000401105 in ?? ()
	(gdb)

Ok, let’s look at this program part with a disassembler:

	objdump -d -M intel /usr/bin/vlc
	[...]
	 4010f9:       e8 32 0a 00 00          call   401b30 <unsetenv>
	 4010fe:       e8 3d fe ff ff          call   400f40 <geteuid@plt>
	 401103:       85 c0                   test   eax,eax
	 401105:       0f 84 04 06 00 00       je     40170f <fflush@plt+0x66f>
	 40110b:       be ca 1f 40 00          mov    esi,0x401fca
	 401110:       bf 06 00 00 00          mov    edi,0x6
	[...]