24 Apr
2017
24 Apr
'17
10:06 p.m.
From: Josh Good
Would the command "cd /tmp ; rm -rf .*" be
able to kill a V6 ... system?
Looking at the vanilla 'rm' source for V6, it cannot/does not delete
directories; one has to use the special 'rmdir' command for that. But,
somewhat to my surprise, it does support both the '-r' and '-f' flags,
which I
thought were later. (Although not as 'stacked' flags, so you'd have to say
'rm -r -f'.)
So, assuming one did that, _and_ (important caveat!) _performed that command
as root_, it probably would empty out the entire directory tree. (I checked,
and "cd /tmp ; echo .*" evaluates to ". .." on V6.
Noel
24 Apr
24 Apr
10:18 p.m.
New subject: There is turmoil in Linux-land - When did rm first avoid going upwards?
On 2017 Apr 24, 18:06, Noel Chiappa wrote:
Yeah, but does "rm" in V6 has a built-in "brake" to not process
"." nor
"..", no matter what ("-f")?
--
Josh Good
From: Josh
Good
Would the command "cd /tmp ; rm -rf .*"
be able to kill a V6 ... system?
So, assuming one did that, _and_ (important caveat!) _performed that command
as root_, it probably would empty out the entire directory tree. (I checked,
and "cd /tmp ; echo .*" evaluates to ". .." on V6. 
11:23 p.m.
New subject: There is turmoil in Linux-land - When did rm first avoid going upwards?
On Tue, Apr 25, 2017 at 12:18:41AM +0200, Josh Good wrote:
On 2017 Apr 24, 18:06, Noel Chiappa wrote:
Yeah, but does "rm" in V6 has a built-in "brake" to not process
"." nor
"..", no matter what ("-f")?
--
Josh Good
rm in V6 outsources globbing to /etc/glob, which appears to report
no-match if the first character is .
https://github.com/dspinellis/unix-history-repo/blob/Research-V6-Snapshot-D…
khm
From:
Josh Good
Would the command "cd /tmp ; rm -rf .*"
be able to kill a V6 ... system?
So, assuming one did that, _and_ (important caveat!) _performed that command
as root_, it probably would empty out the entire directory tree. (I checked,
and "cd /tmp ; echo .*" evaluates to ". .." on V6. 
11:59 p.m.
New subject: was turmoil, moving to rm -rf /
This is gonna seem like I'm tooting my own horn, and I am a little, but
here's an rm -rf / story.
Clem will be amused because I was a junior or senior in college and a sys
admin for a Masscomp with a 40MB disk with 20 users. And I did some version
of rm -rf /, realized part way through that I screwed up, and killed it.
But /bin and /dev were gone so putting things back together was hard.
But I did it and wrote up this little note for the people who came after
me, if I was stupid enough to do this someone else would, was my thinking.
You can get a sense of how scared I was in it if you read it carefully.
It was a very long night.
For an undergrad, I think it's not bad? Maybe? I dunno, I look at how
much I needed to have understood to get the system back up, that's a lot
of reading, playing, experience. Love that Geophysics department, they
pushed me.
And it was during my (brief) foray into the *roff -me macros (I went
-ms and never looked back). Roff source on request to anyone who is
twisted enough to want it.
http://mcvoy.com/lm/masscomp-restore.pdf
Complete with all the typos.
--lm
25 Apr
25 Apr
12:44 a.m.
New subject: was turmoil, moving to rm -rf /
Am I the only one who mentally says, "f*ck recursively" whenever I type,
"rm -fr" ? (f*ck being fsck, of course.)
On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com> wrote:
This is gonna seem like I'm tooting my own horn,
and I am a little, but
here's an rm -rf / story.
Clem will be amused because I was a junior or senior in college and a sys
admin for a Masscomp with a 40MB disk with 20 users. And I did some
version
of rm -rf /, realized part way through that I screwed up, and killed it.
But /bin and /dev were gone so putting things back together was hard.
But I did it and wrote up this little note for the people who came after
me, if I was stupid enough to do this someone else would, was my thinking.
You can get a sense of how scared I was in it if you read it carefully.
It was a very long night.
For an undergrad, I think it's not bad? Maybe? I dunno, I look at how
much I needed to have understood to get the system back up, that's a lot
of reading, playing, experience. Love that Geophysics department, they
pushed me.
And it was during my (brief) foray into the *roff -me macros (I went
-ms and never looked back). Roff source on request to anyone who is
twisted enough to want it.
http://mcvoy.com/lm/masscomp-restore.pdf
Complete with all the typos.
--lm
2:02 p.m.
New subject: was turmoil, moving to rm -rf /
Larry,
I had to laugh when I read that because what you don't know is it was part
of my old Unix wizards test which was left over from a the day when one of
our hackers (whom I think you would later get to know so I'll not name him)
accidentally typed: rm -rf . as root from his / on his workstation.
Because /bin/rmdir had been lost, he started getting errors when rmdir was
forked. So he hit ^C, but he had already lost: /bin, /dev, /etc, /lib,
most of /usr. He was a developer in the networking group so he was working
on network code which we could not trust would not panic (in fact we
disconnected the node from the ethernet immediately just in case). But we
did have pretty much everything in /usr/bin/[s-z]* -- that is we think it
was deleting files in /usr/bin when he stopped it.
We obviously had another working Masscomp box just like it. And of course
the shell was working on the machine that was in trouble. We recovered
the system as it was. Hint the key item is you have to start by putting
/dev back together and the solution to that problem has had been discussed
on this list.
Clem
On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com> wrote:
This is gonna seem like I'm tooting my own horn,
and I am a little, but
here's an rm -rf / story.
Clem will be amused because I was a junior or senior in college and a sys
admin for a Masscomp with a 40MB disk with 20 users. And I did some
version
of rm -rf /, realized part way through that I screwed up, and killed it.
But /bin and /dev were gone so putting things back together was hard.
But I did it and wrote up this little note for the people who came after
me, if I was stupid enough to do this someone else would, was my thinking.
You can get a sense of how scared I was in it if you read it carefully.
It was a very long night.
For an undergrad, I think it's not bad? Maybe? I dunno, I look at how
much I needed to have understood to get the system back up, that's a lot
of reading, playing, experience. Love that Geophysics department, they
pushed me.
And it was during my (brief) foray into the *roff -me macros (I went
-ms and never looked back). Roff source on request to anyone who is
twisted enough to want it.
http://mcvoy.com/lm/masscomp-restore.pdf
Complete with all the typos.
--lm
2:08 p.m.
New subject: was turmoil, moving to rm -rf /
Whoever was the genuis that put mknod in /etc has my gratitude.
We had other working Masscomp boxen but after I screwed up that
badly nobody would let me near them until I fixed mine :)
And you have to share who it was, I admitted I did it, I think
it's just a thing many people do..... Once :)
On Tue, Apr 25, 2017 at 10:02:26AM -0400, Clem Cole wrote:
Larry,
I had to laugh when I read that because what you don't know is it was part
of my old Unix wizards test which was left over from a the day when one of
our hackers (whom I think you would later get to know so I'll not name him)
accidentally typed: rm -rf . as root from his / on his workstation.
Because /bin/rmdir had been lost, he started getting errors when rmdir was
forked. So he hit ^C, but he had already lost: /bin, /dev, /etc, /lib,
most of /usr. He was a developer in the networking group so he was working
on network code which we could not trust would not panic (in fact we
disconnected the node from the ethernet immediately just in case). But we
did have pretty much everything in /usr/bin/[s-z]* -- that is we think it
was deleting files in /usr/bin when he stopped it.
We obviously had another working Masscomp box just like it. And of course
the shell was working on the machine that was in trouble. We recovered
the system as it was. Hint the key item is you have to start by putting
/dev back together and the solution to that problem has had been discussed
on this list.
Clem
On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com> wrote:
> This is gonna seem like I'm tooting my own horn, and I am a little, but
> here's an rm -rf / story.
>
> Clem will be amused because I was a junior or senior in college and a sys
> admin for a Masscomp with a 40MB disk with 20 users. And I did some
> version
> of rm -rf /, realized part way through that I screwed up, and killed it.
> But /bin and /dev were gone so putting things back together was hard.
>
> But I did it and wrote up this little note for the people who came after
> me, if I was stupid enough to do this someone else would, was my thinking.
> You can get a sense of how scared I was in it if you read it carefully.
> It was a very long night.
>
> For an undergrad, I think it's not bad? Maybe? I dunno, I look at how
> much I needed to have understood to get the system back up, that's a lot
> of reading, playing, experience. Love that Geophysics department, they
> pushed me.
>
> And it was during my (brief) foray into the *roff -me macros (I went
> -ms and never looked back). Roff source on request to anyone who is
> twisted enough to want it.
>
> http://mcvoy.com/lm/masscomp-restore.pdf
>
> Complete with all the typos.
>
> --lm
>
--
---
Larry McVoy lm at mcvoy.com http://www.mcvoy.com/lm
2:12 p.m.
New subject: was turmoil, moving to rm -rf /
I did it during my IBM days years ago. It was an AIX 4.2, I broke almost a
half of /usr and /bin /etc... ashamed :-(
Álvaro
2017-04-25 16:08 GMT+02:00 Larry McVoy <lm(a)mcvoy.com>om>:
Whoever was the genuis that put mknod in /etc has my
gratitude.
We had other working Masscomp boxen but after I screwed up that
badly nobody would let me near them until I fixed mine :)
And you have to share who it was, I admitted I did it, I think
it's just a thing many people do..... Once :)
On Tue, Apr 25, 2017 at 10:02:26AM -0400, Clem Cole wrote:
Larry,
I had to laugh when I read that because what you don't know is it was
part
of my old Unix wizards test which was left over
from a the day when one
of
our hackers (whom I think you would later get to
know so I'll not name
him)
accidentally typed: rm -rf . as root from his /
on his workstation.
Because /bin/rmdir had been lost, he started getting errors when rmdir
was
forked. So he hit ^C, but he had already lost:
/bin, /dev, /etc, /lib,
most of /usr. He was a developer in the networking group so he was
working
on network code which we could not trust would
not panic (in fact we
disconnected the node from the ethernet immediately just in case). But
we
did have pretty much everything in
/usr/bin/[s-z]* -- that is we think it
was deleting files in /usr/bin when he stopped it.
We obviously had another working Masscomp box just like it. And of course
the shell was working on the machine that was in trouble. We recovered
the system as it was. Hint the key item is you have to start by putting
/dev back together and the solution to that problem has had been
discussed
on this list.
Clem
On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com> wrote:
> This is gonna seem like I'm tooting my own horn, and I am a little, but
> here's an rm -rf / story.
>
> Clem will be amused because I was a junior or senior in college and a
sys
> admin for a Masscomp with a 40MB disk with
20 users. And I did some
> version
> of rm -rf /, realized part way through that I screwed up, and killed
it.
> But /bin and /dev were gone so putting
things back together was hard.
>
> But I did it and wrote up this little note for the people who came
after
> me, if I was stupid enough to do this
someone else would, was my
thinking.
> You can get a sense of how scared I was in
it if you read it carefully.
> It was a very long night.
>
> For an undergrad, I think it's not bad? Maybe? I dunno, I look at how
> much I needed to have understood to get the system back up, that's a
lot
> of reading, playing, experience. Love that
Geophysics department, they
> pushed me.
>
> And it was during my (brief) foray into the *roff -me macros (I went
> -ms and never looked back). Roff source on request to anyone who is
> twisted enough to want it.
>
> http://mcvoy.com/lm/masscomp-restore.pdf
>
> Complete with all the typos.
>
> --lm
>
--
---
Larry McVoy lm at mcvoy.com
http://www.mcvoy.com/lm
2:29 p.m.
New subject: was turmoil, moving to rm -rf /
I too, on a 4.1 BSD or 4.2 BSD vax 780 at Ga Tech. I forget who helped
me put things back together. IIRC I had blown away "only" /dev, so it
wasn't quite so bad.
But yes, it's something you only do once. :-)
Arnold
Álvaro Jurado <elbingmiss(a)gmail.com> wrote:
I did it during my IBM days years ago. It was an AIX
4.2, I broke almost a
half of /usr and /bin /etc... ashamed :-(
Álvaro
2017-04-25 16:08 GMT+02:00 Larry McVoy <lm(a)mcvoy.com>om>:
> Whoever was the genuis that put mknod in /etc has my gratitude.
> We had other working Masscomp boxen but after I screwed up that
> badly nobody would let me near them until I fixed mine :)
>
> And you have to share who it was, I admitted I did it, I think
> it's just a thing many people do..... Once :)
>
> On Tue, Apr 25, 2017 at 10:02:26AM -0400, Clem Cole wrote:
> > Larry,
> >
> > I had to laugh when I read that because what you don't know is it was
> part
> > of my old Unix wizards test which was left over from a the day when one
> of
> > our hackers (whom I think you would later get to know so I'll not name
> him)
> > accidentally typed: rm -rf . as root from his / on his workstation.
> >
> > Because /bin/rmdir had been lost, he started getting errors when rmdir
> was
> > forked. So he hit ^C, but he had already lost: /bin, /dev, /etc, /lib,
> > most of /usr. He was a developer in the networking group so he was
> working
> > on network code which we could not trust would not panic (in fact we
> > disconnected the node from the ethernet immediately just in case). But
> we
> > did have pretty much everything in /usr/bin/[s-z]* -- that is we think it
> > was deleting files in /usr/bin when he stopped it.
> >
> > We obviously had another working Masscomp box just like it. And of course
> > the shell was working on the machine that was in trouble. We recovered
> > the system as it was. Hint the key item is you have to start by putting
> > /dev back together and the solution to that problem has had been
> discussed
> > on this list.
> >
> > Clem
> >
> > On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com> wrote:
> >
> > > This is gonna seem like I'm tooting my own horn, and I am a little,
but
> > > here's an rm -rf / story.
> > >
> > > Clem will be amused because I was a junior or senior in college and a
> sys
> > > admin for a Masscomp with a 40MB disk with 20 users. And I did some
> > > version
> > > of rm -rf /, realized part way through that I screwed up, and killed
> it.
> > > But /bin and /dev were gone so putting things back together was hard.
> > >
> > > But I did it and wrote up this little note for the people who came
> after
> > > me, if I was stupid enough to do this someone else would, was my
> thinking.
> > > You can get a sense of how scared I was in it if you read it carefully.
> > > It was a very long night.
> > >
> > > For an undergrad, I think it's not bad? Maybe? I dunno, I look at
how
> > > much I needed to have understood to get the system back up, that's a
> lot
> > > of reading, playing, experience. Love that Geophysics department, they
> > > pushed me.
> > >
> > > And it was during my (brief) foray into the *roff -me macros (I went
> > > -ms and never looked back). Roff source on request to anyone who is
> > > twisted enough to want it.
> > >
> > > http://mcvoy.com/lm/masscomp-restore.pdf
> > >
> > > Complete with all the typos.
> > >
> > > --lm
> > >
>
> --
> ---
> Larry McVoy lm at mcvoy.com
> http://www.mcvoy.com/lm
>
2:31 p.m.
New subject: was turmoil, moving to rm -rf /
My mstake was forgetting that "su -" is not "su". So I thought I was
on the
right dir and...
Álvaro
2017-04-25 16:29 GMT+02:00 <arnold(a)skeeve.com>om>:
I too, on a 4.1 BSD or 4.2 BSD vax 780 at Ga Tech. I
forget who helped
me put things back together. IIRC I had blown away "only" /dev, so it
wasn't quite so bad.
But yes, it's something you only do once. :-)
Arnold
Álvaro Jurado <elbingmiss(a)gmail.com> wrote:
I did it during my IBM days years ago. It was an
AIX 4.2, I broke almost
a
half of /usr and /bin /etc... ashamed :-(
Álvaro
2017-04-25 16:08 GMT+02:00 Larry McVoy <lm(a)mcvoy.com>om>:
> Whoever was the genuis that put mknod in /etc has my gratitude.
> We had other working Masscomp boxen but after I screwed up that
> badly nobody would let me near them until I fixed mine :)
>
> And you have to share who it was, I admitted I did it, I think
> it's just a thing many people do..... Once :)
>
> On Tue, Apr 25, 2017 at 10:02:26AM -0400, Clem Cole wrote:
> > Larry,
> >
> > I had to laugh when I read that because what you don't know is it was
> part
> > of my old Unix wizards test which was left over from a the day when
one
> of
> > our hackers (whom I think you would later get to know so I'll not
name
> him)
> > accidentally typed: rm -rf . as root from his / on his workstation.
> >
> > Because /bin/rmdir had been lost, he started getting errors when
rmdir
> was
> > forked. So he hit ^C, but he had already lost: /bin, /dev, /etc,
/lib,
> > most of /usr. He was a developer in
the networking group so he was
> working
> > on network code which we could not trust would not panic (in fact we
> > disconnected the node from the ethernet immediately just in case).
But
> we
> > did have pretty much everything in /usr/bin/[s-z]* -- that is we
think
it
> > was deleting files in /usr/bin when he
stopped it.
> >
> > We obviously had another working Masscomp box just like it. And of
course
> > the shell was working on the machine
that was in trouble. We
recovered
> > the system as it was. Hint the key
item is you have to start by
putting
> > /dev back together and the solution to
that problem has had been
> discussed
> > on this list.
> >
> > Clem
> >
> > On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com> wrote:
> >
> > > This is gonna seem like I'm tooting my own horn, and I am a
little, but
> > > here's an rm -rf / story.
> > >
> > > Clem will be amused because I was a junior or senior in college
and
a
> sys
> > > admin for a Masscomp with a 40MB disk with 20 users. And I did
some
> > > version
> > > of rm -rf /, realized part way through that I screwed up, and
killed
> it.
> > > But /bin and /dev were gone so putting things back together was
hard.
> > >
> > > But I did it and wrote up this little note for the people who came
> after
> > > me, if I was stupid enough to do this someone else would, was my
> thinking.
> > > You can get a sense of how scared I was in it if you read it
carefully.
> > > It was a very long night.
> > >
> > > For an undergrad, I think it's not bad? Maybe? I dunno, I look
at how
> > > much I needed to have understood
to get the system back up, that's
a
> lot
> > > of reading, playing, experience. Love that Geophysics department,
they
> > > pushed me.
> > >
> > > And it was during my (brief) foray into the *roff -me macros (I
went
> > > -ms and never looked back). Roff
source on request to anyone who
is
> > > twisted enough to want it.
> > >
> > > http://mcvoy.com/lm/masscomp-restore.pdf
> > >
> > > Complete with all the typos.
> > >
> > > --lm
> > >
>
> --
> ---
> Larry McVoy lm at mcvoy.com
> http://www.mcvoy.com/lm
>
4:28 p.m.
New subject: was turmoil, moving to rm -rf /
On 25/04/2017 15:31, Álvaro Jurado wrote:
My mstake was forgetting that "su -" is not
"su". So I thought I was on
the right dir and...
Not for quite the same reason, but on all my machines I've taken to
creating a home directory for root that isn't / for the last couple of
decades.
--
Pete
Pete Turnbull
27 Apr
27 Apr
11:44 p.m.
New subject: was turmoil, moving to rm -rf /
The worst "nuke the file system" experience I had was on the GE
mainframe. Think big room, punched cards, etc. And an operators'
console that typed on paper...
When you booted the system, the first message that came up said:
INIT?
If you said 'y', it wiped out the file system.
After a very heated users' group meeting, they agreed to change the
message to
DO YOU WANT TO WIPE OUT THE FILE SYSTEM?
11:54 p.m.
New subject: was turmoil, moving to rm -rf /
Exec 8 (the Univac Operating Systm) used to make you type the word “CATASTROPHIC” to
proceed past a certain point in reiniting the system.
28 Apr
28 Apr
3:04 a.m.
New subject: was turmoil, moving to rm -rf /
On 2017-04-27 7:44 PM, Steve Johnson wrote:
The worst "nuke the file system" experience
I had was on the GE
mainframe. Think big room, punched cards, etc. And an operators'
console that typed on paper...
When you booted the system, the first message that came up said:
INIT?
If you said 'y', it wiped out the file system.
After a very heated users' group meeting, they agreed to change the
message to
DO YOU WANT TO WIPE OUT THE FILE SYSTEM?
Good to know UX has always been terrible :-)
--T
5:19 a.m.
New subject: was turmoil, moving to rm -rf /
Toby Thain <toby(a)telegraphics.com.au> wrote:
On 2017-04-27 7:44 PM, Steve Johnson wrote:
Well golly gee whiz, the guy who wrote it knew what it was
going to do ... ( :-)
Arnold
The worst "nuke the file system"
experience I had was on the GE
mainframe. Think big room, punched cards, etc. And an operators'
console that typed on paper...
When you booted the system, the first message that came up said:
INIT?
If you said 'y', it wiped out the file system.
After a very heated users' group meeting, they agreed to change the
message to
DO YOU WANT TO WIPE OUT THE FILE SYSTEM?
Good to know UX has always been terrible :-)
--T
25 Apr
25 Apr
2:18 p.m.
New subject: was turmoil, moving to rm -rf /
Problem was /etc has been burned too... so the mknod command is off the
table.
On Tue, Apr 25, 2017 at 10:08 AM, Larry McVoy <lm(a)mcvoy.com> wrote:
Whoever was the genuis that put mknod in /etc has my
gratitude.
We had other working Masscomp boxen but after I screwed up that
badly nobody would let me near them until I fixed mine :)
And you have to share who it was, I admitted I did it, I think
it's just a thing many people do..... Once :)
On Tue, Apr 25, 2017 at 10:02:26AM -0400, Clem Cole wrote:
Larry,
I had to laugh when I read that because what you don't know is it was
part
of my old Unix wizards test which was left over
from a the day when one
of
our hackers (whom I think you would later get to
know so I'll not name
him)
accidentally typed: rm -rf . as root from his /
on his workstation.
Because /bin/rmdir had been lost, he started getting errors when rmdir
was
forked. So he hit ^C, but he had already lost:
/bin, /dev, /etc, /lib,
most of /usr. He was a developer in the networking group so he was
working
on network code which we could not trust would
not panic (in fact we
disconnected the node from the ethernet immediately just in case). But
we
did have pretty much everything in
/usr/bin/[s-z]* -- that is we think it
was deleting files in /usr/bin when he stopped it.
We obviously had another working Masscomp box just like it. And of course
the shell was working on the machine that was in trouble. We recovered
the system as it was. Hint the key item is you have to start by putting
/dev back together and the solution to that problem has had been
discussed
on this list.
Clem
On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com> wrote:
> This is gonna seem like I'm tooting my own horn, and I am a little, but
> here's an rm -rf / story.
>
> Clem will be amused because I was a junior or senior in college and a
sys
> admin for a Masscomp with a 40MB disk with
20 users. And I did some
> version
> of rm -rf /, realized part way through that I screwed up, and killed
it.
> But /bin and /dev were gone so putting
things back together was hard.
>
> But I did it and wrote up this little note for the people who came
after
> me, if I was stupid enough to do this
someone else would, was my
thinking.
> You can get a sense of how scared I was in
it if you read it carefully.
> It was a very long night.
>
> For an undergrad, I think it's not bad? Maybe? I dunno, I look at how
> much I needed to have understood to get the system back up, that's a
lot
> of reading, playing, experience. Love that
Geophysics department, they
> pushed me.
>
> And it was during my (brief) foray into the *roff -me macros (I went
> -ms and never looked back). Roff source on request to anyone who is
> twisted enough to want it.
>
> http://mcvoy.com/lm/masscomp-restore.pdf
>
> Complete with all the typos.
>
> --lm
>
--
---
Larry McVoy lm at mcvoy.com
http://www.mcvoy.com/lm
3:28 p.m.
New subject: was turmoil, moving to rm -rf /
On Tue, Apr 25, 2017 at 10:18 AM, Clem Cole <clemc(a)ccc.com> wrote:
Problem was /etc has been burned too... so the mknod
command is off the
table.
Either boot into standalone media like some kind of miniroot (that
hopefully has a copy of mknod) or look for some kind of shell builtin?
E.g., if the shell provides some mechanism to make a raw system call, you
can do it. E.g., an escape hatch to syscall() or indir(). If a copy of
`mkdir` survived, then on older systems where directory creation was done
by calling mknod(), one might be able to modify `mkdir` enough to create
device file for a tape device to launch a restore off of. I thought some
systems came with a syscall(1) utility, but it does't seem to be current
anymore and I can't find any references to it so perhaps I'm misremembering.
I once messed up a NeXT machine by "mv"'ing the system shared libraries to
an unexpected path. Oops. I had to boot off the CD to fix it, but that's
child's play compared to some of the esoterica you guys are talking about.
- Dan C.
On Tue, Apr 25, 2017 at 10:08 AM, Larry McVoy <lm(a)mcvoy.com> wrote:
Whoever was the genuis that put mknod in /etc has
my gratitude.
We had other working Masscomp boxen but after I screwed up that
badly nobody would let me near them until I fixed mine :)
And you have to share who it was, I admitted I did it, I think
it's just a thing many people do..... Once :)
On Tue, Apr 25, 2017 at 10:02:26AM -0400, Clem Cole wrote:
Larry,
I had to laugh when I read that because what you don't know is it was
part
of my old Unix wizards test which was left over
from a the day when one
of
our hackers (whom I think you would later get to
know so I'll not name
him)
accidentally typed: rm -rf . as root from his /
on his workstation.
Because /bin/rmdir had been lost, he started getting errors when rmdir
was
forked. So he hit ^C, but he had already lost:
/bin, /dev, /etc,
/lib,
most of /usr. He was a developer in the
networking group so he was
working
on network code which we could not trust would
not panic (in fact we
disconnected the node from the ethernet immediately just in case).
But we
did have pretty much everything in
/usr/bin/[s-z]* -- that is we think
it
was deleting files in /usr/bin when he stopped
it.
We obviously had another working Masscomp box just like it. And of
course
the shell was working on the machine that was in
trouble. We recovered
the system as it was. Hint the key item is you have to start by
putting
/dev back together and the solution to that
problem has had been
discussed
on this list.
Clem
On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com> wrote:
> This is gonna seem like I'm tooting my own horn, and I am a little,
but
> here's an rm -rf / story.
>
> Clem will be amused because I was a junior or senior in college and a
sys
> admin for a Masscomp with a 40MB disk with
20 users. And I did some
> version
> of rm -rf /, realized part way through that I screwed up, and killed
it.
> But /bin and /dev were gone so putting
things back together was hard.
>
> But I did it and wrote up this little note for the people who came
after
> me, if I was stupid enough to do this
someone else would, was my
thinking.
> You can get a sense of how scared I was in
it if you read it
carefully.
> It was a very long night.
>
> For an undergrad, I think it's not bad? Maybe? I dunno, I look at
how
> much I needed to have understood to get the
system back up, that's a
lot
> of reading, playing, experience. Love that
Geophysics department,
they
> pushed me.
>
> And it was during my (brief) foray into the *roff -me macros (I went
> -ms and never looked back). Roff source on request to anyone who is
> twisted enough to want it.
>
> http://mcvoy.com/lm/masscomp-restore.pdf
>
> Complete with all the typos.
>
> --lm
>
--
---
Larry McVoy lm at mcvoy.com
http://www.mcvoy.com/lm
5:56 p.m.
New subject: was turmoil, moving to rm -rf /
I once had to rebuild the root directory using ROM based disk IO and memory peek and poke
commands! At this late date I don’t recall many details but at least the root block was
trashed during some last minute testing. Unlikely it was “rm -rf / something” as that
would’ve done far more damage.
The situation was this:
1. We had *one* working hardware system[1].
2. At that time we only had working floppy controller and driver[2].
3. Our devel system was a VAX running 4.1BSD. no support for the floppy drive so
everything had to be downloaded over a 9600 serial link.
4. The backup floppy either didn’t exist or wasn’t readable.
5. We had custom stuff that was done for a show and not backed up anywhere.
Luckily, due to earlier debugging sessions I knew what the file system layout was — this
was on a version 7 system, with 16 byte dir entries, 2 bytes inode #, followed by and 14
byte name. IIRC inode 0 was not used, inode 1 was used as a temp during fsck based
recovery and inode 2 was for the real root. So I read in the root inode, found the disk
address of its data block, read it in, using fixed up “.” and “..” and “/bin” entries —
usually inode #3 was bin, wrote it back to the floppy and rebooted. I think the unix image
was in /bin. On reboot fsck worked and reconnected all the lost directories, which were
easy to figure out and rename.
The back story is that this happened on a Saturday just before the Fall Comdex 1981, where
we were going to show our system for the first time and we had to take a working system to
Las Vegas by Sunday[3]. We were able to fly out on time and the Comdex show was a success,
with thousands of leads generated.
In terms of lessons, I don’t know what we learned. I guess it pays to be intimately
familiar with the system as we were in an extreme bootstrap situation with very little
working reliably. Seems often startups end up doing acrobatics without a net!
— bakul
[1] Two actually, but the second was a wire wrapped prototype. This was at an early Unix
workstation startup; our main app was “word processing”.
[2] Later we hooked up a Western Digital ST506 controller via parallel port and I was very
happy when my disk driver could do 25 KB/s! No DMA so had to do programmed IO.
[3] Rob Warnock (whom some of you may know from his SGI days) was our very hands-on CTO,
and he was/is great at debugging/problem solving. I don’t know why they waited for me
rather than call Rob. a) I was a junior engineer as that my first job with C & Unix
(6 months at that time) and b) I had already worked about 80+ hours that week and gone
home to sleep at 9AM on Saturday. May be Rob was smart enough to not answer his phone!
On Apr 25, 2017, at 8:28 AM, Dan Cross
<crossd(a)gmail.com> wrote:
On Tue, Apr 25, 2017 at 10:18 AM, Clem Cole <clemc(a)ccc.com
<mailto:clemc@ccc.com>> wrote:
Problem was /etc has been burned too... so the mknod command is off the table.
Either boot into standalone media like some kind of miniroot (that hopefully has a copy
of mknod) or look for some kind of shell builtin? E.g., if the shell provides some
mechanism to make a raw system call, you can do it. E.g., an escape hatch to syscall() or
indir(). If a copy of `mkdir` survived, then on older systems where directory creation was
done by calling mknod(), one might be able to modify `mkdir` enough to create device file
for a tape device to launch a restore off of. I thought some systems came with a
syscall(1) utility, but it does't seem to be current anymore and I can't find
any references to it so perhaps I'm misremembering.
I once messed up a NeXT machine by "mv"'ing the system shared libraries to
an unexpected path. Oops. I had to boot off the CD to fix it, but that's child's
play compared to some of the esoterica you guys are talking about.
- Dan C.
On Tue, Apr 25, 2017 at 10:08 AM, Larry McVoy <lm(a)mcvoy.com
<mailto:lm@mcvoy.com>> wrote:
Whoever was the genuis that put mknod in /etc has my gratitude.
We had other working Masscomp boxen but after I screwed up that
badly nobody would let me near them until I fixed mine :)
And you have to share who it was, I admitted I did it, I think
it's just a thing many people do..... Once :)
On Tue, Apr 25, 2017 at 10:02:26AM -0400, Clem Cole wrote:
Larry,
I had to laugh when I read that because what you don't know is it was part
of my old Unix wizards test which was left over from a the day when one of
our hackers (whom I think you would later get to know so I'll not name him)
accidentally typed: rm -rf . as root from his / on his workstation.
Because /bin/rmdir had been lost, he started getting errors when rmdir was
forked. So he hit ^C, but he had already lost: /bin, /dev, /etc, /lib,
most of /usr. He was a developer in the networking group so he was working
on network code which we could not trust would not panic (in fact we
disconnected the node from the ethernet immediately just in case). But we
did have pretty much everything in /usr/bin/[s-z]* -- that is we think it
was deleting files in /usr/bin when he stopped it.
We obviously had another working Masscomp box just like it. And of course
the shell was working on the machine that was in trouble. We recovered
the system as it was. Hint the key item is you have to start by putting
/dev back together and the solution to that problem has had been discussed
on this list.
Clem
On Mon, Apr 24, 2017 at 7:59 PM, Larry McVoy <lm(a)mcvoy.com
<mailto:lm@mcvoy.com>> wrote:
> This is gonna seem like I'm tooting my own horn, and I am a little, but
> here's an rm -rf / story.
>
> Clem will be amused because I was a junior or senior in college and a sys
> admin for a Masscomp with a 40MB disk with 20 users. And I did some
> version
> of rm -rf /, realized part way through that I screwed up, and killed it.
> But /bin and /dev were gone so putting things back together was hard.
>
> But I did it and wrote up this little note for the people who came after
> me, if I was stupid enough to do this someone else would, was my thinking.
> You can get a sense of how scared I was in it if you read it carefully.
> It was a very long night.
>
> For an undergrad, I think it's not bad? Maybe? I dunno, I look at how
> much I needed to have understood to get the system back up, that's a lot
> of reading, playing, experience. Love that Geophysics department, they
> pushed me.
>
> And it was during my (brief) foray into the *roff -me macros (I went
> -ms and never looked back). Roff source on request to anyone who is
> twisted enough to want it.
>
> http://mcvoy.com/lm/masscomp-restore.pdf
<http://mcvoy.com/lm/masscomp-restore.pdf>
>
> Complete with all the typos.
>
> --lm
>
--
---
Larry McVoy lm at mcvoy.com <http://mcvoy.com/>
http://www.mcvoy.com/lm <http://www.mcvoy.com/lm>
2:19 p.m.
New subject: was turmoil, moving to rm -rf /
I had to laugh when I read that because what you
don't know is it was part
of my old Unix wizards test which was left over from a the day when one of
our hackers (whom I think you would later get to know so I'll not name him)
accidentally typed: rm -rf . as root from his / on his workstation.
Because /bin/rmdir had been lost, he started getting errors when rmdir was
forked. So he hit ^C, but he had already lost: /bin, /dev, /etc, /lib,
most of /usr. He was a developer in the networking group so he was working
on network code which we could not trust would not panic (in fact we
disconnected the node from the ethernet immediately just in case). But we
did have pretty much everything in /usr/bin/[s-z]* -- that is we think it
was deleting files in /usr/bin when he stopped it.
It was in a situation similar to this that I learned the blessed
usefulness of echo * as a crude substitute for /bin/ls
--corey
12:06 a.m.
New subject: There is turmoil in Linux-land - When did rm first avoid going upwards?
rm in V6 outsources globbing to /etc/glob, which
appears to report
no-match if the first character is .
Actually, it's the shell that calls glob. Glob then invokes the command
(in this case rm).
Anyhow, that doesn't do what you think it does. It ignores directory
entries that begin with '.' if the search string doesn't begin with ..
".*" will indeed match ".."
Of course, the calamity depends on whether you have /tmp on it's own
filesystem. V6 didn't go .. off the top of the filesystem, the root ..
just linked back to the inode 1 (the root itself).
12:18 a.m.
New subject: There is turmoil in Linux-land - When did rm first avoid going upwards?
On Mon, Apr 24, 2017 at 08:06:28PM -0400, Ron Natalie wrote:
Thanks for correcting my hasty conclusions. /usr/source/s2/rm.c has an
execl call in the rm() function, but I didn't dig further into the
calling mechanism.
V7's /usr/src/cmd/rm.c definitely explicitly has a check for '..' and
an error message dedicated to the task.
So I think we can conclude that unix got this protection sometime
between V6 and V7 -- in other words, sometime in the late 1970s.
And systemd is now catching up. "Those who do not study unix" etc
khm
rm in V6 outsources globbing to /etc/glob, which
appears to report
no-match if the first character is .
Actually, it's the shell that calls glob. Glob then invokes the command
(in this case rm).
Anyhow, that doesn't do what you think it does. It ignores directory
entries that begin with '.' if the search string doesn't begin with ..
".*" will indeed match ".."
Of course, the calamity depends on whether you have /tmp on it's own
filesystem. V6 didn't go .. off the top of the filesystem, the root ..
just linked back to the inode 1 (the root itself).
12:22 a.m.
New subject: There is turmoil in Linux-land - When did rm first avoid going upwards?
On Mon, Apr 24, 2017 at 5:18 PM Kurt H Maier <khm(a)sciops.net> wrote:
And systemd is now catching up. "Those who do not study unix" etc
not catching up, as I read the discussion it is marked as "working as
intended".
12:24 a.m.
New subject: There is turmoil in Linux-land - When did rm first avoid going upwards?
On Tue, Apr 25, 2017 at 12:22:44AM +0000, ron minnich wrote:
On Mon, Apr 24, 2017 at 5:18 PM Kurt H Maier
<khm(a)sciops.net> wrote:
They committed a patch to fix it. The project maintainer declared it a
non-problem ex post facto and met with some derision... but by that
point they at least had a safeguard in place.
khm
And systemd is now catching up. "Those who do not study unix" etc
not catching up, as I read the discussion it is marked as "working as
intended".
12:26 a.m.
New subject: There is turmoil in Linux-land - When did rm first avoid going upwards?
On Mon, Apr 24, 2017 at 5:24 PM Kurt H Maier <khm(a)sciops.net> wrote:
They committed a patch to fix it. The project maintainer declared it a
non-problem ex post facto and met with some derision... but by that
point they at least had a safeguard in place.
khm
ah, good to know.
2553
days inactive
2557
days old
23 comments
15 participants
participants (15)
-
arnold＠skeeve.com -
Bakul Shah -
Clem Cole -
corey＠lod.com -
Dan Cross -
jnc＠mercury.lcs.mit.edu -
Josh Good -
Kurt H Maier -
Larry McVoy -
Pete Turnbull -
ron minnich -
Ron Natalie -
Steve Johnson -
Toby Thain -
Álvaro Jurado