This note details the process of building a working v6 instance from a copy of the original tape distribution. The v6 instance runs in a virtual PDP-11/40 provided by OpenSIMH, a masterwork emulator.

Last Updated on October 19, 2022.

This is an updated and revised version of this note.

The primary motivator for this revision is the formation of the Open SIMH steering committee and their taking on the maintenance and care of SIMH going forward. Secondarily, it’s been 7 years since I originally wrote the note and I wanted to bring it up to date. The note is intended to document the process of running v6 in the PDP-11/40 emulated environment that Open SIMH provides.

Helpful Sites

This note details the process of building a working v6 instance from a copy of the original tape distribution. It is worth noting that calling them original bits, as would be obtained from the original tape could be misleading. There are a number of different versions extant, but the Unix Heritage Society, hereafter referred to as TUHS, has provided the public access to all of the versions they believe to most closely match the original tape.

System Requirements

Getting Started

This section describes creating a workspace, downloading the images, and building the enblock and deblock utilities.

Create a working directory

I use retro-workarea/v6 in my home folder)

mkdir -p ~/retro-workarea/v6
cd ~/retro-workarea/v6

Get a copy of the distribution tape image

curl -O https://www.tuhs.org/Archive/Distributions/Research/Ken_Wellsch_v6/v6.tape.gz

Get a copy of Wolfgang’s fixes and the enblock and deblock program source code

curl -O https://www.tuhs.org/Archive/Distributions/Research/Bug_Fixes/V6enb/v6enb.tar.gz

Unpack the two archives

gunzip v6.tape.gz
tar xvf v6enb.tar.gz

Build the enblock and deblock utilities

Warnings are non-fatal and are related to the dialect of C that Wolfgang is using:

cd v6enb
cc -Wno-implicit-function-declaration enblock.c -o enblock
cc -Wno-implicit-function-declaration deblock.c -o deblock

Copy the utilities into the working directory and change into that directory:

cp enblock ..
cp deblock ..
cd ..

Tape Preparation

This section describes preparing the raw v6 tape image for use with the Open SimH emulator using the enblock utility program. enblock converts a raw tape image into a format that Open SimH expects (512 byte blocks, file size markers, and eof marker):

Use enblock to read v6.tape and convert it into dist.tap

./enblock < v6.tape > dist.tap

Boot from the converted distribution tape - The ini method

Create a tape boot ini file for Open SimH that will initialize the tape and give us access to the tmrk utility for copying from tape directly to disk without the need for much of an os:

cat > tboot.ini << "EOF"
set cpu 11/40
set tm0 locked
attach tm0 dist.tap
set rk0 en noautosize
set rk1 en noautosize
set rk2 en noautosize
set rk3 en noautosize
attach rk0 rk0
attach rk1 rk1
attach rk2 rk2
attach rk3 rk3
d cpu 100000 012700
d cpu 100002 172526
d cpu 100004 010040
d cpu 100006 012740
d cpu 100010 060003
d cpu 100012 000777
g 100000
EOF

I will explain the contents of the ini file in the next section on the manual method.

Start the Open SimH PDP-11 emulator with tboot.ini

pdp11 tboot.ini

What you will see is:

PDP-11 simulator V4.0-0 Current        git commit id: 65410851
Disabling XQ
tboot.ini-3> attach tm0 dist.tap
%SIM-INFO: TM0: Tape Image 'dist.tap' scanned as SIMH format
tboot.ini-4> attach rk0 rk0
%SIM-INFO: RK0: Creating new file: rk0
tboot.ini-5> attach rk1 rk1
%SIM-INFO: RK1: Creating new file: rk1
tboot.ini-6> attach rk2 rk2
%SIM-INFO: RK2: Creating new file: rk2
tboot.ini-7> attach rk3 rk3
%SIM-INFO: RK3: Creating new file: rk3

Note: The output will contain the absolute path to tboot.ini, I removed it to make the output cleaner.

Halt the Simulator

Halt the CPU by typing CTRL+E - the machine will break at 100012 and will display:

Simulation stopped, PC: 100012 (BR 100012)

Boot from the converted distribution tape - The manual method

Start the Open SimH PDP-11 emulator

pdp11

PDP-11 simulator V4.0-0 Current        git commit id: 65410851

Tell Open SimH that the model we want is PDP-11/40

sim>  set cpu 11/40
Disabling XQ

Create a magnetic tape device on drive 0, set it locked for write:

sim> set tm0 locked

Attach the converted distribution tape to the magnetic tape device:

sim> attach tm0 dist.tap
%SIM-INFO: TM0: Tape Image 'dist.tap' scanned as SIMH format

Enable rk? and set it to noautosize:

sim> set rk0 en noautosize
sim> set rk1 en noautosize
sim> set rk2 en noautosize
sim> set rk3 en noautosize

Create three empty formatted disk packs on drives 0, 1, and 2 and attach them as RK05 devices:

sim> attach rk0 rk0
%SIM-INFO: RK0: Creating new file: rk0
sim> attach rk1 rk1
%SIM-INFO: RK1: Creating new file: rk1
sim> attach rk2 rk2
%SIM-INFO: RK2: Creating new file: rk2

Key in and execute a program at memory location 100000 that loads the tape at address 0. After telling Open SimH that we intend to insert data into memory, the emulator will display successive word locations. We are providing octal bytes 2, at a time, to match the word size of the PDP-11:

sim> id 100000-100012
100000: 012700
100002: 172526
100004: 010040
100006: 012740
100010: 060003
100012: 000777

Execute the loaded program:

simh> g 100000

Halt the CPU by typing CTRL+E - the machine will break at 100012 and will display:

Simulation stopped, PC: 100012 (BR 100012)

Notes up to this point

The tape has virtually moved and the CPU looped (according to Setting up Unix). Halting and restarting the CPU will cause the tape to rewind. The next step will start the program now residing at CPU 0. At this point, I believe that we have loaded the minimal OS from the tape. The tape is composed of 512-byte blocks:

  • Blocks 0 - 100 are the tape bootstrap stuff
  • Blocks 101 - 4100 are the RK05 root image
  • Blocks 4101 - 8100 are the /usr RK05 image
  • Blocks 8101 - 12100 are the /doc RK05 image.

Boot blocks for various types of device are stored at different locations:

  • Block 100 is the RK05 boot block
  • Block 99 is the RP03 boot block
  • Block 98 is the RP04 boot block

If you want to use a different source device than the default TU10 (which is what we configured as tm0 attached to dist.tap), or target than RK05 (which is what we configured as rk0), you will need to modify the commands below to use the correct utility and offset for the correct boot block. Here are the rules from Setting Up Unix - Sixth Edition:

If you have TU16 tape say ‘htrk’ instead of ‘tmrk’ in the above example. If you have an RP03 disk, say ‘tmrp’ or ‘htrp’, and use a 99 instead of 100 tape offset. If you have an RP04 disk, use ‘tmhp’ or ‘hthp’ instead or ‘tmrk’, and use a 98 instead of 100 tape offset. The different offsets load bootstrap programs appropriate to the disk they will live on.

At this point, all we are interested in are getting the bootstrap program and the root image in order to be able to boot from disk.

Copy tape objects to disk

assumes TU10 and RK05 devices, which we selected in tboot.ini

Run the minimal os loaded at address 0

g 0
=

Use the tmrk utility to copy the disk bootstrap program from tape to the disk block 0:

=tmrk
disk offset
0
tape offset
100
count
1

Use tmrk to copy the root filesystem (tape position 101-4100) to disk

=tmrk
disk offset
1
tape offset
101
count
3999
=

CTRL+E to break the emulation

Simulation stopped, PC: 137274 (TSTB @#177560)

sim> q
Goodbye

Boot from disk

simh has a built in boot rom for bootstrapping the disk and loading it’s bootblock

cat > dboot.ini << "EOF"
set cpu 11/40
set tto 7b
set tm0 locked
attach tm0 dist.tap
set rk0 en noautosize
set rk1 en noautosize
set rk2 en noautosize
set rk3 en noautosize
attach rk0 rk0
attach rk1 rk1
attach rk2 rk2
attach rk3 rk3
attach ptr ptr.txt
attach ptp ptp.txt
attach lpt lpt.txt
dep system sr 173030
boot rk0
EOF

Notes

  • set tto 7b - set the terminal output to 7 bits, which is compatible with Unix v6.
  • attach rk3 rk3 - added an extra disk that we can use later… or not…
  • attach ptr ptr.txt - added a paper tape reader virtual device which will come in handy to transfer files from the host to v6.
  • attach ptp ptp.txt - added a paper tape punch virtual device which will be useful for transferring files from v6 to the host.
  • attach lpt lpt.txt - added a virtual line printer that will allow us to print things to the host from v6
  • dep system sr 173030 - Unix will boot the system in single user mode (xref, man 8 boot procedures in v6)
  • boot rk0 - boot using the disk that we installed a boot loader and root filesystem to

Start the Simulator

pdp11 dboot.ini
PDP-11 simulator V4.0-0 Current        git commit id: 65410851
Disabling XQ
dboot.ini-4> attach tm0 dist.tap
%SIM-INFO: TM0: Tape Image 'dist.tap' scanned as SIMH format
dboot.ini-13> attach ptr ptr.txt
%SIM-INFO: PTR: creating new file
dboot.ini-14> attach ptp ptp.txt
%SIM-INFO: PTP: creating new file
dboot.ini-15> attach lpt lpt.txt
%SIM-INFO: LPT: creating new file
@

The @ symbol is the boot loader prompt. We tell it where the kernel is in relation to our filesystem:

@rkunix
mem = 1035
RESTRICTED RIGHTS
Use, duplication or disclosure is subject to
restrictions stated in Contract with Western
Electric Company, Inc.
#

If you stop here an look around there will be a number of really interesting, but annoying things happening. Feel free to stop at this point and just get a feel for how alien, but familiar the OS is…

There are some annoyances:

  • The first annoyance is that uppercase nonsense. To fix:

#STTY -LCASE

  • The second annoyance is the complete lack of a cd command. To fix, you will need to read on.

Configuration and Installation of a new kernel

Note that even in 1975, a rebuild of the kernel only took 50 seconds.

Build mkconf

mkconf is what configures the system to support various device types

chdir /usr/sys/conf
cc mkconf.c
mv a.out mkconf

Run mkconf

Tell it about our attached devices - rk05’s, tape reader and tape punch, magtape, DECtape, serial terminals, and line printer:

./mkconf
rk
pc
tm
tc
8dc
lp
done

Compile and install the kernel

We will call it unix. Some things to know up front:

  • m40.s is the machine language assist file
  • c.c is the configuration table containing the major device switches for each device class, block or character
  • l.s is the trap vectors for the devices
as m40.s
mv a.out m40.o
cc -c c.c
as l.s
ld -x a.out m40.o c.o ../lib1 ../lib2
mv a.out /unix

Confirm that the resulting kernel is 30k

ls -l /unix
-rwxrwxrwx  1 root    30942 Oct 10 13:04 unix

Create and configure devices

Prior to making dev mods, the directory contains:

ls /dev
kmem
mem
null
tty8

Each of these files is described in section IV of the manual on v6

Take a look at c.c to understand the device numbers

cat c.c
/*
*/
int     (*bdevsw[])()
{
&nulldev,       &nulldev,       &rkstrategy,    &rktab, /* rk */
&nodev,         &nodev,         &nodev,         0,      /* rp */
&nodev,         &nodev,         &nodev,         0,      /* rf */
&tmopen,        &tmclose,       &tmstrategy,    &tmtab, /* tm */
&nulldev,       &tcclose,       &tcstrategy,    &tctab, /* tc */
&nodev,         &nodev,         &nodev,         0,      /* hs */
&nodev,         &nodev,         &nodev,         0,      /* hp */
&nodev,         &nodev,         &nodev,         0,      /* ht */
0
};
int     (*cdevsw[])()
{
&klopen,   &klclose,  &klread,   &klwrite,  &klsgtty,   /* console */
&pcopen,   &pcclose,  &pcread,   &pcwrite,  &nodev,     /* pc */
&lpopen,   &lpclose,  &nodev,    &lpwrite,  &nodev,     /* lp */
&dcopen,   &dcclose,  &dcread,   &dcwrite,  &dcsgtty,   /* dc */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* dh */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* dp */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* dj */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* dn */
&nulldev,  &nulldev,  &mmread,   &mmwrite,  &nodev,     /* mem */
&nulldev,  &nulldev,  &rkread,   &rkwrite,  &nodev,     /* rk */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* rf */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* rp */
&tmopen,   &tmclose,  &tmread,   &tmwrite,  &nodev,     /* tm */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* hs */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* hp */
&nodev,    &nodev,    &nodev,    &nodev,    &nodev,     /* ht */
0
};
int     rootdev {(0<<8)|0};
int     swapdev {(0<<8)|0};
int     swplo   4000;   /* cannot be zero */
int     nswap   872;

Note that rk is block device major 0 (the first entry in the array) and that rrk is character device major 9, and so on.

Create Special Files

Create special files for each installed device that isn’t already there. If you paste these, be careful and if you have any issues try pasting fewer lines at a time:

/etc/mknod /dev/rk0 b 0 0
/etc/mknod /dev/rk1 b 0 1
/etc/mknod /dev/rk2 b 0 2
/etc/mknod /dev/rk3 b 0 3
/etc/mknod /dev/mt0 b 3 0
/etc/mknod /dev/tap0 b 4 0
/etc/mknod /dev/rrk0 c 9 0
/etc/mknod /dev/rrk1 c 9 1
/etc/mknod /dev/rrk2 c 9 2
/etc/mknod /dev/rrk3 c 9 3
/etc/mknod /dev/rmt0 c 12 0
/etc/mknod /dev/ppt c 1 0
/etc/mknod /dev/lp0 c 2 0
/etc/mknod /dev/tty0 c 3 0
/etc/mknod /dev/tty1 c 3 1
/etc/mknod /dev/tty2 c 3 2
/etc/mknod /dev/tty3 c 3 3
/etc/mknod /dev/tty4 c 3 4
/etc/mknod /dev/tty5 c 3 5
/etc/mknod /dev/tty6 c 3 6
/etc/mknod /dev/tty7 c 3 7

Secure the special files:

chmod 640 /dev/*rk*
chmod 640 /dev/*pp*
chmod 640 /dev/*lp*
chmod 640 /dev/*mt*
chmod 640 /dev/*tap*
chmod 640 /dev/*tty*

Install the sources and docs

In order to have a usable system, we will still need to install the sources, the docs, mount them, and edit the rc, and ttys file, and modify and rebuild the df command (I may revisit this note later as Ritchie’s notes refer to some other files that need to change).

Restore doc and source from rk05s

dd if=/dev/rmt0 of=/dev/rrk1 count=4000 skip=4100
4000+0 records in
4000+0 records out

dd if=/dev/rmt0 of=/dev/rrk2 count=4000 skip=8100
4000+0 records in
4000+0 records out

Update the superblock

ensures that all output gets written to disk

sync
sync
sync

Create mount point for doc and source as needed

Create mount point for doc and mount both doc and source (source mountpoint already exists)

mkdir /usr/doc
/etc/mount /dev/rk1 /usr/source
/etc/mount /dev/rk2 /usr/doc

Test that both now have files

ls /usr/source
...

ls /usr/doc
...

Add mounts to rc

use cat - CTRL+D will tell cat that it has hit EOF

cat >> /etc/rc
/etc/mount /dev/rk1 /usr/source
/etc/mount /dev/rk2 /usr/doc

CTRL+D

Modify df

Modify df to show disk free on all devices using ed, the only delivered editor, see below for an ed cheatsheet. I have added rk3, even though, technically it doesn’t have a filesystem to check… yet.

chdir /usr/source/s1
ed df.c
5p
5d
4
i
"/dev/rk0",
"/dev/rk1",
.
7
i
"/dev/rk3",
.
w
q

Compile df

cc df.c

Test df

# ./a.out
/dev/rk0 991
/dev/rk1 935
/dev/rk2 1691
/dev/rk3 bad free count
0

Note: rk3 doesn’t have a file system on it… yet.

Install the new df

cp a.out /bin/df

Test the new df

df
/dev/rk0 989
/dev/rk1 935
/dev/rk2 1691
/dev/rk3 bad free count
0

Check the drives that have filesystems

icheck /dev/rrk0
/dev/rrk0:
spcl      25
files    294
large     96
direc     25
indir     96
used    2924
free     989

dcheck /dev/rrk0
/dev/rrk0:
 
icheck /dev/rrk1
/dev/rrk1:
spcl       0
files    596
large     98
direc     34
indir     98
used    2978
free     935
 
dcheck /dev/rrk1
/dev/rrk1:

icheck /dev/rrk2
/dev/rrk2:
spcl       0
files    337
large     69
direc     25
indir     69
used    2222
free    1691

dcheck /dev/rrk2
/dev/rrk2:

Modify ttys

Modify ttys to enable devices 1-8, these are serial consoles, which we will enable in the final version of our Open SimH ini file:

ed /etc/ttys
1,8s/^0/1/p
w
q

Update the superblock and power off

sync
sync
CTRL-E
sim> q

The system is functional at this point, but some post installation configuration is helpful/advisable.

Post Install Notes

The system is ready for a normal multiuser boot with all of the devices attached.

Create a normal boot ini file

cat > nboot.ini << "EOF"
set cpu 11/40
set cpu idle
set tto 7b
set tm0 locked
set rk0 en noautosize
set rk1 en noautosize
set rk2 en noautosize
set rk3 en noautosize
attach rk0 rk0
attach rk1 rk1
attach rk2 rk2
attach rk3 rk3
attach ptr ptr.txt
attach ptp ptp.txt
attach lpt lpt.txt
set dci en
set dci lines=8
set dco 7b
att dci 5555
boot rk0
EOF

Boot for the First Time

pdp11 nboot.ini

PDP-11 simulator V4.0-0 Current        git commit id: 65410851
Disabling XQ
/Users/wsenn/retro-workarea/v6/nboot.ini-19> att dci 5555
%SIM-INFO: Listening on port 5555
@

Load the unix kernel

@unix

login as root, with no password

Speed up the Terminal CR and LF

stty cr0 nl0

Test “printing” from the Simulation

If you set up the lp device correctly, lp0 is a character device where text can be redirected, and picked up by simh.

cat /etc/rc > /dev/lp0

Pause the simulator to get it to write to the lpt file:

sim> CTRL-E

then on the host, open the lpt.txt file

Restart the sim:

sim> cont

Add man Command

mount wolfgang’s man.enb tape in the simuation

CTRL-E to suspend the simulation simh> attach tm0 v6enb/man.enb

%SIM-INFO: TM0: Tape Image ‘v6enb/man.enb’ scanned as SIMH format

sim> co

list the files on the tape —- tp tm

sav res man0/naa.df man0/tocrc.df man3/pow.3.df man3/printf.3.df man3/rand.3.df man5/fs.5.df man5/a.out.5.df man6/factor.6.df man6/primes.6.df /usr/bin/man /usr/source/s7/nroff1.s

13 entries 45 used 107 last

the tape contains a save and restore script, a number fo diff files, the man script, and an nroff1.s assembly file

restore the files from the tape into /usr/doc/man —- chdir /usr/doc/man tp xm res cat res

restore the files (modify some files) —- sh res The error /usr/source/s7/nroff1.s.df: cannot open does is not fatal and the man command will work fine.

test man —- man man

– test that a telnet session from the host works ——————————————————————— open a terminal telnet localhost 5555 note the escape character is ^] press enter if the word login doesn’t immediately appear

login stty nl0 cr0 ls

CTRL-D to logout of v6

CTRL-] to close the telnet session

q to quit telnet altogether

CTRL-D again to close the terminal

– test copying text files to and from the simulator ——————————————————————— because we set up rk03 and ppt above, we can either read and write from /dev/rk03 or /dev/ppt this test is for the paper tape device, see the longer note on Copying Files for more information —-

on the host, put some text in the ptr.txt file

–snip Hello, v6 from the HOST!!! –snip

in v6, read the file from the ppt device —- cat > myfile < /dev/ppt cat myfile Hello, v6 from the HOST!!!#

in v6, write the file to the ppt device —- cat myfile > /dev/ppt sync

CTRL-E to suspend the simulation co to resume v6

on the host, read the ptp file

  • as of 20151120.0642pm, it appears to be necessary to suspend the simulator to get anything written to the device. This can be done multiple times, as needed.

    – Set up users in v6 ——————————————————————— @unix cat » /etc/passwd wsenn::10:1::/usr/wsenn: CTRL+D

mkdir /usr/wsenn chown wsenn /usr/wsenn login wsenn pwd /usr/wsenn

sync sync sync

CTRL+E to break the emulation sim> q ——————————————————————— – Back up the working instance (baseline) ——————————————————————— mkdir baseline-v6 cp nboot.ini baseline-v6/ cp rk? baseline-v6/ tar cvzf baseline-v6.tar.gz baseline-v6 cp baseline-v6.tar.gz ../ rm -fr baseline-v6*

test the backup —- cd .. tar xvf baseline-v6.tar.gz cd baseline-v6 pdp11 nboot.ini

PDP-11 simulator V4.0-0 Current git commit id: 65410851 Disabling XQ /Users/wsenn/retro-workarea/baseline-v6/nboot.ini-13> attach ptr ptr.txt %SIM-INFO: PTR: creating new file /Users/wsenn/retro-workarea/baseline-v6/nboot.ini-14> attach ptp ptp.txt %SIM-INFO: PTP: creating new file /Users/wsenn/retro-workarea/baseline-v6/nboot.ini-15> attach lpt lpt.txt %SIM-INFO: LPT: creating new file /Users/wsenn/retro-workarea/baseline-v6/nboot.ini-19> att dci 5555 %SIM-INFO: Listening on port 5555 @unix

login: wsenn %

CTRL-E simh>q

cd .. rm -fr ./baseline-v6 cd v6

– add cd command using host editor and reading and writing from ppt ——————————————————————— Note: sh is critically important, don’t muck it up :). The issue is that if you do, there really isn’t an easy way to recover. Just be careful and don’t replace the original shell until you have tested the build. The idea of this fix is simply to add a cd command handler to the existing code. I chose to exactly mimic chdir and use the chdir command itself for simplicity and less chance of error.

pdp11 nboot.ini

@unix root stty cr0 nl0

cat to the paper tape punch —- cat /usr/source/s2/sh.c > /dev/ppt

CTRL-E to suspend the sim (ensure that the device complete’s its write) co to continue

open ptp.txt in your favorite editor that doesn’t muck with the invisible characters copy it’s contents except for the header and footer lines, but be sure to get every non-header or footer character

edit it by changing: if(equal(cp1, “chdir”)) { if(t[DCOM+1] != 0) { if(chdir(t[DCOM+1]) < 0) err(“chdir: bad directory”); } else err(“chdir: arg count”); return; } to: if(equal(cp1, “chdir”)) { if(t[DCOM+1] != 0) { if(chdir(t[DCOM+1]) < 0) err(“chdir: bad directory”); } else err(“chdir: arg count”); return; } if(equal(cp1, “cd”)) { if(t[DCOM+1] != 0) { if(chdir(t[DCOM+1]) < 0) err(“cd: bad directory”); } else err(“cd: arg count”); return; }

paste it into ptr.txt, be sure to copy from the initial # to the end and include an empty line

in v6, read from ppt into a new file —- CTRL-E to suspend detach ptr attach ptr ptr.txt co

cat > sh.c.new < /dev/ppt

compare the new file to the old file —- diff sh.c.new /usr/source/s2/sh.c 569,576d568

  • if(equal(cp1, “cd”)) {
  • if(t[DCOM+1] != 0) {
  • if(chdir(t[DCOM+1]) < 0)
  • err(“cd: bad directory”);
  • } else
  • err(“cd: arg count”);
  • return;
  • }

figure out how to build and install sh —- chdir /usr/source/s2 cp sh.c sh.c.original cp /sh.c.new sh.c

grep sh run cc -s -n -O sh.c cmp a.out /bin/sh cp a.out /bin/sh

build and install sh —-

cc -s -n -O sh.c cmp a.out /bin/sh a.out /bin/sh differ: char 4, line 1 ./a.out test that it works - should display a shell prompt and act in every way identically to the previous shell, with the exception that cd should now work. If it doesn’t you will likely need to halt the simulation and reboot. Only if it works, copy it over the original after backing the original up.

mv /bin/sh /bin/sh.original cp a.out /bin/sh chown bin /bin/sh

CTRL-D relogin

cd /usr Woohoo! CTRL-E q

Make a backup baseline-v6-withcd

mkdir baseline-v6-withcd cp nboot.ini baseline-v6-withcd/ cp rk? baseline-v6-withcd/ tar cvzf baseline-v6-withcd.tar.gz baseline-v6-withcd cp baseline-v6-withcd.tar.gz ../ rm -fr baseline-v6-withcd*

– Copying Files ——————————————————————— ** ** From Unix v6 on PDP-11/40 Open SimH to Host: **

create and attach an additional rk device, if not already attached —- simh> attach rk3 rk3 co

get a file of interest and note it’s size in bytes —-

ls -l /etc/rc

-rw-rw-r– 1 bin 90 Oct 10 12:32 /etc/rc

look at the od dump of the file for comparison later —-

od -c /etc/rc

0000000 r m - f / e t c / m t a b \n 0000020 / e t c / u p d a t e \n / e t c 0000040 / m o u n t / d e v / r k 1
0000060 / u s r / s o u r c e \n / e t c 0000100 / m o u n t / d e v / r k 2
0000120 / u s r / d o c \n \n 0000132

write the file to the rk device (the sync may not be needed, but the result looks cleaner, also it doesn’t apper that you can specify bs=1, device errors out) —- dd if=/etc/rc of=/dev/rrk3 conv=sync 0+1 records in 1+0 records out

exit the sim and then on the host, read from the rk image using bs=1 and count from the ls output —- $ dd if=rk3 of=rc ibs=1 count=90 90+0 records in 90+0 records out

look at the od dump —- $ od -c rc 0000000 r m - f / e t c / m t a b \n 0000020 / e t c / u p d a t e \n / e t c 0000040 / m o u n t / d e v / r k 1
0000060 / u s r / s o u r c e \n / e t c 0000100 / m o u n t / d e v / r k 2
0000120 / u s r / d o c \n \n
0000132

A match!

** From Host to Unix v6 on PDP11/40 Open SimH Host: **

make a minor edit to the rc file (change m to n in the word mtab) and note it’s size in bytes —- $ ls -l rc -rw-r–r– 1 wsenn staff 90 Oct 19 15:54 rc

it better be 90, unless I did something other than changing a letter

write rc to a new rk3 file —- $ rm rk3 $ dd if=rc of=rk3 conv=sync 0+1 records in 1+0 records out 512 bytes transferred in 0.000037 secs (13854733 bytes/sec) note the count of blocks

with the number of blocks on hand, fire up the simulation and read from the rk to disk —-

dd if=/dev/rrk3 of=rc.dd count=1

because of the fact that I can’t specify bs=1, the result is padded —- od -c rc.dd 0000000 r m - f / e t c / n t a b \n 0000020 / e t c / u p d a t e \n / e t c 0000040 / m o u n t / d e v / r k 1 0000060 / u s r / s o u r c e \n / e t c 0000100 / m o u n t / d e v / r k 2 0000120 / u s r / d o c \n \n \0 \0 \0 \0 \0 \0 0001000

read from the dd file with the number of bytes still in hand —- dd if=rc.dd of=rc bs=1 count=90 90+0 records in 90+0 records out

then diff the file against the original: —- diff rc /etc/rc 1c1

  • rm -f /etc/ntab

    . rm -f /etc/mtab

Success!

– Some confusing, but special points to remember ——————————————————————— there is no vi, use ed (see below) there is no cd, use chdir (unless you followed the cd instructions)

(hash) characters are not good for pasting, they require an escape #

ctime.README points the way to successfully compiling stuff: sometimes you need to be bin, login as bin with no password the correct command to add an object to a lib is: ar r ../lib2 myfile.o

to learn how to compile stuff, the run script in the source directories are good skeletons. to see how to compile login.c in /usr/source/s1 chdir /usr/source/s1 ed login.c and make any changes you desire (such as fixing the login: prompt which shows Name: on subsequent retries)

if you can’t remember the right commands to compile and install this program, do the following: grep login run cc -s -O login.c cmp a.out /bin/login cp a.out /bin/login

to see who needs to do the compiling ls -l /bin/login -rwsr-xr-x 1 root 2606 Oct 10 14:19 /bin/login

looks like root in this case, whereas for getty.c: grep getty run cc -s -n -O getty.c cmp a.out /etc/getty cp a.out /etc/getty ls -l /etc/getty -rwxrwxr– 1 bin 1002 Oct 10 14:09 /etc/getty looks like bin.

As noted in ctime.README, run in /usr/sys does not actually update the libraries

Before you update libraries, ls -l to see the mode and ownership of the files ls -l /usr/sys/lib? -rw-rw-r– 1 bin 59342 Oct 10 13:17 lib1 -rw-rw-r– 1 bin 48630 Oct 10 13:18 lib2

if you try to remove a special file (whatever that is), it will display a mode that is six digits long.

rm /usr/sys/lib1 /usr/sys/lib1: 110664 mode

man 2 stat

The flags are as follows: 100000 i-node is allocated 060000 2-bit file type: 000000 plain file 040000 directory 020000 character-type special file 060000 block-type special file. 010000 large file 004000 set user-ID on execution 002000 set group-ID on execution 001000 save text image after execution 000400 read (owner) 000200 write (owner) 000100 execute (owner) 000070 read, write, execute (group) 000007 read, write, execute (others)

that makes 110664 read: the i-node is allocated, it’s a large file, it’s a plain file, and it is rw-rw-r–.

– ed cheatsheet ——————————————————————— ed is the editor, there is no vi ed is ok, here’s a quick cheat sheet

m,nC - m is a starting line number, n is an ending line number, C is command The current line is the default target for a command

a - append c - change d - delete i - insert p - print

e - edit file f - file being edited r - read file w - write file . ends input

s/this/that

– Command Help ———————————————————————

  • find - find files

this command is tricky, but once you get the hang of it, works great!

to find a file use the following syntax -a means “and” and is absolutely required: find / -name tty.h -a -print /usr/sys/tty.h

to find a pattern is straightforward: find / -name “tty*” -a -print

post added 2022-12-02 17:52:00 -0600