Why does the Linux kernel support "umount /"?

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                          Why does Linux support this:

    umount /

Why would anyone write that, instead of this:

    mount / -oremount,ro

I'm looking at the kernel code here:

	if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
		/*
		 * Special case for "unmounting" root ...
		 * we just try to remount it readonly.
		 */
		if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
			return -EPERM;
		down_write(&sb->s_umount);
		if (!sb_rdonly(sb))
			retval = do_remount_sb(sb, SB_RDONLY, NULL, 0);

https://elixir.bootlin.com/linux/v4.18/source/fs/namespace.c#L1612 
                        

Asked by sourcejedi (53232 rep)

Sep 3, 2018, 09:51 AM
Last activity: Jul 20, 2023, 03:09 PM

Why does the Linux kernel support "umount /"?

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