# Safe Mode



## Geezer (Apr 18, 2021)

In the boot menu, `Boot Options` brings up `Safe Mode`, `Single User` and `Verbose`.

It is in 13.0. Maybe it was in previous versions, but I did not notice.

Anyway, I know what single user and verbose mean. What is Safe Mode? I thought that was some peculiarity of windows.


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## mark_j (Apr 18, 2021)

It's not new, it's been around for a long time.
Basically it starts FreeBSD with no SMP, no DMA on various I/O buses, won't probe for devices, do integrity checks on hard disks/SSDs etc etc. I think, basically, it's like Windows safe mode in that it doesn't load a lot of stuff that could be causing your problem; whatever that problem should be. It does permit networking.

(At least that's what it used to do, it may have changed over the years).


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## grahamperrin@ (Apr 18, 2021)

mark_j said:


> no SMP, no DMA on various I/O buses, won't probe for devices, do integrity checks on hard disks/SSDs etc








						menu-commands.4th « forth « stand - src - FreeBSD source tree
					






					cgit.freebsd.org
				









						core.lua « lua « stand - src - FreeBSD source tree
					






					cgit.freebsd.org


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## mark_j (Apr 18, 2021)

Haha, so my notes are still good, although, wasn't Forth abandoned by FreeBSD in favour of LUA?


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## grahamperrin@ (Apr 18, 2021)

Good point.

I see <https://cgit.freebsd.org/src/tree/stand/lua> but <https://gitlab.com/search?search=set kern.smp.disabled&project_id=19317362&group_id=765080> finds `set kern.smp.disabled` in only one file. I don't know my way around the code.


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## mark_j (Apr 18, 2021)

It's in core.lua, lines 173 onwards.


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## grahamperrin@ (Apr 18, 2021)

Thanks! I edited a link into my first comment.


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## grahamperrin@ (Mar 10, 2022)

FreeBSD bug 260812 – Safe boot (safe mode): improve documentation

(This topic was mentioned in IRC.)


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