CentOS – Why Booting into Rescue Mode Menu Doesn’t Do Anything?

bootcentosgrub2rescue

When I enter into grub menu, I get two entries :

CentOS Linux (3.10.0-514.21.1.el7.x86_64) 7 (Core)
CentOS Linux (0-rescue-e1ac24cbe9f94f2caa228d77e027be8b) 7 (Core)

When I boot into the second line (the rescue one), I get a normal prompt like if I had boot into the first line. I was expecting someting like a rescue shell or something equivalent to single-user mode but it still asking me for root password, root FS is not in read only mode etc. Nothing seems different from multi-user mode.

Can someone try on its distro to see if it has the same behavior? I'm pretty new to rescue, emergency, single-user modes so I might have missed someting.

Here is my conf :

[root@centos3 ~]# uname -a
Linux centos3 3.10.0-327.el7.x86_64 #1 SMP Thu Nov 19 22:10:57 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

[root@centos3 ~]# cat /etc/redhat-release
CentOS Linux release 7.3.1611 (Core)

Best Answer

it still asking me for root password, root FS is not in read only mode

This is the norm for systemd's rescue mode and thus for systemd operating systems. For not (re-)mounting filesystems and a read-only / mount, you should look to emergency mode, which is not the same as rescue mode. Both emergency and rescue modes invoke sulogin on systemd operating systems. The differences between the twain lie in how much of the basic system is brought up, and what is mounted.

Note that single user mode was superseded by the split mechanisms of emergency mode and rescue mode in 1995, when van Smoorenburg init gained its -b option.

The other answer is talking about something else that is also confusingly called "rescue mode", as well as referencing the CentOS 5 doco for CentOS 7 even though CentOS 7 is a systemd operating system whereas CentOS 5 was not.

That "rescue mode" involves bootstrapping another operating system image from a CD-ROM, DVD-ROM, or USB storage device. This rescue mode and emergency mode involve what you are talking about in the question: entries on the GRUB menu and stuff that you can edit into the kernel command line from that very same GRUB menu.

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