xref: /freebsd/share/man/man8/rescue.8 (revision 7963c02c9bc222e8ac8c1a3acb87451bd74b9733)

.\" Copyright (c) 2003 Tim Kientzle <kientzle@acm.org>
.\" Copyright (c) 2003 Simon L. Nielsen <simon@FreeBSD.org>
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.\" $FreeBSD$
.\"
.Dd June 30, 2022
.Dt RESCUE 8
.Os
.Sh NAME
.Nm rescue
.Nd rescue utilities in
.Pa /rescue
.Sh DESCRIPTION
The
.Pa /rescue
directory contains a collection of common utilities intended for use
in recovering a badly damaged system.
With the transition to a dynamically-linked root beginning with
.Fx 5.2 ,
there is a real possibility that the standard tools in
.Pa /bin
and
.Pa /sbin
may become non-functional due to a failed upgrade or a disk error.
The tools in
.Pa /rescue
are statically linked and should therefore be more resistant to
damage.
However, being statically linked, the tools in
.Pa /rescue
are also less functional than the standard utilities.
In particular, they do not have full use of the locale,
.Xr pam 3 ,
and nsswitch libraries.
.Pp
If your system fails to boot, and it shows a prompt similar to:
.Pp
.Dl "Enter full pathname of shell or RETURN for /bin/sh: "
.Pp
the first thing to try running is the standard shell,
.Pa /bin/sh .
If that fails, try running
.Pa /rescue/sh ,
which is the
.Nm
shell.
To repair the system, the root partition must first be remounted
read-write.
This can be done with the following
.Xr mount 8
command:
.Pp
.Dl "/rescue/mount -uw /"
.Pp
The next step is to double-check the contents of
.Pa /bin , /sbin ,
and
.Pa /usr/lib ,
possibly mounting a
.Fx
rescue or
.Dq "live file system"
CD-ROM and copying files from there.
Once it is possible to successfully run
.Pa /bin/sh , /bin/ls ,
and other standard utilities, try rebooting back into the standard
system.
.Pp
The
.Pa /rescue
tools are compiled using
.Xr crunchgen 1 ,
which makes them considerably more compact than the standard
utilities.
To build a
.Fx
system where space is critical,
.Pa /rescue
can be used as a replacement for the standard
.Pa /bin
and
.Pa /sbin
directories; simply change
.Pa /bin
and
.Pa /sbin
to be symbolic links pointing to
.Pa /rescue .
Since
.Pa /rescue
is statically linked, it should also be possible to dispense with much
of
.Pa /usr/lib
in such an environment.
.Pp
In contrast to its predecessor
.Pa /stand ,
.Pa /rescue
is updated during normal
.Fx
source and binary upgrades.
.Sh FILES
.Bl -tag -width ".Pa /rescue" -compact
.It Pa /rescue
Root of the
.Nm
hierarchy.
.El
.Sh SEE ALSO
.Xr crunchgen 1 ,
.Xr crash 8
.Sh HISTORY
The
.Nm
utilities first appeared in
.Fx 5.2 .
.Sh AUTHORS
.An -nosplit
The
.Nm
system was written by
.An Tim Kientzle Aq Mt kientzle@FreeBSD.org ,
based on ideas taken from
.Nx .
This manual page was written by
.An Simon L. Nielsen Aq Mt simon@FreeBSD.org ,
based on text by
.An Tim Kientzle Aq Mt kientzle@FreeBSD.org .
.Sh BUGS
Most of the
.Nm
tools work even in a fairly crippled system.
The most egregious exception is the
.Nm
version of
.Xr vi 1 ,
which currently requires that
.Pa /usr
be mounted so that it can access the
.Xr termcap 5
files.
Hopefully, a failsafe
.Xr termcap 3
entry will eventually be added into the
.Xr ncurses 3
library, so that
.Pa /rescue/vi
can be used even in a system where
.Pa /usr
cannot immediately be mounted.
In the meantime, the
.Nm
version of the
.Xr ed 1
editor can be used from
.Pa /rescue/ed
if you need to edit files, but cannot mount
.Pa /usr .