~ecs/ecs.d2evs.net

7b0bd6f973a101ca28b7787f08645efa5f31bddc — Eyal Sawady 6 months ago
Initial commit

Includes framework as well as two articles I've had lying around for a
while.
A  => .gitignore +1 -0
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_site

A  => LICENSE +350 -0
@@ 1,350 @@
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A  => Makefile +7 -0
@@ 1,7 @@
upload:
	wersh input _site
	ssh ecs@d2evs.net rm -r /var/www/ecs.d2evs.net/posts
	rsync -r _site/ ecs@d2evs.net:/var/www/ecs.d2evs.net

clean:
	rm -r _site

A  => README.md +13 -0
@@ 1,13 @@
# My blog

The code behind <https://ecs.d2evs.net>.

## Technical details

I use [wersh](https://git.sr.ht/~sircmpwn/wersh) and
[discount](http://www.pell.portland.or.us/~orc/Code/discount/), you may
have luck with other markdown preprocessors.

## Licensing

CC-BY-SA

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@@ 1,186 @@
% # vim: set ft=markdown :
% preprocessor="markdown -f fencedcode"
# Adventures installing OpenWRT

I recently got my
[MikroTik RB2011U](https://openwrt.org/toh/mikrotik/rb2011uias), and I
wanted to install OpenWRT on it.

The MikroTik RouterBOARD has a "Netinstall" mode, in which it connects
to `eth1` and receives a kernel to boot from using TFTP[^0]. I ended up
with this small script, based on something from the OpenWRT
documentation:

[^0]: The Trivial File Transfer Protocol.

```
#!/bin/sh

# Replace `enp2s0f1` with your ethernet interface

# Serve TFTP from $TFTP_DIR/$TFTP_FILE

TFTP_DIR=~/tmp/openwrt
TFTP_FILE=stable.elf

sudo ifconfig enp2s0f1 192.168.1.10 up

sudo dnsmasq -i enp2s0f1 --dhcp-range=192.168.1.100,192.168.1.200 \
  --dhcp-boot=$TFTP_FILE --enable-tftp --tftp-root=$TFTP_DIR \
  --enable-tftp -d -u $USER -p0 -K --log-dhcp --bootp-dynamic
```

Once the router attempted to connect to the DHCP server with the
hostname `OpenWrt`, I killed the TFTP server.

This worked - the router was now running OpenWRT from RAM.

Then, I disconnected my laptop from `eth1` and plugged it into `eth2`.
The OpenWRT initramfs is configured to act as a DHCP server on `eth2`
through `eth10`.

At this point, I `ssh`ed into the router:

```
$ ssh root@OpenWrt
```

(In the future, commands starting with `$` are on the host computer, and
commands starting with `#` are on the router.)

I now had a root shell on the router! So far so good.

I then `scp`ed the OpenWRT sysupgrade[^1] onto the router:

[^1]: OpenWRT has a `sysupgrade` command which takes a firmware image
      and installs it. The install procedure for MikroTik RouterBOARDs
      is to run OpenWRT from RAM using TFTS, then use `sysupgrade` to
      flash a firmware upgrade.

```
$ scp ~/tmp/openwrt/stable.bin root@OpenWrt:/tmp/sysupgrade.bin
```

and proceeded to `sysupgrade` the router:

```
# sysupgrade /tmp/sysupgrade.bin
Image metadata not found
Cannot save config while running from ramdisk.
Commencing upgrade. Closing all shell sessions.
```

At this point, the router closed the SSH connection and entered a boot
loop.

Huh.

That's interesting.

I tried repeating the previous steps, replacing stable (18.06.4) OpenWRT
with the snapshot. (The RB2011U v2 is listed as only supported by
OpenWRT snapshot.)

No luck.

In vain, I tried pinging the router as it boot looped. It never
responded.

This meant that it was crashing and burning *before* networking was
initialized. (This also meant that OpenWRT failsafe mode wouldn't help.)

So, I tried to read the kernel logs from flash memory:

```
# mount /dev/mtdblock6 /mnt
mount: mounting /dev/mtdblock6 on /mnt/ failed: Invalid argument
```

Maybe I need to specify the filesystem type? JFFS2 seems likely:

```
# mount -t jffs2 /dev/mtdblock6 /mnt
## (hangs for a *really* long time)
mount: mounting /dev/mtdblock6 on /mnt/ failed: Invalid argument
```

That last case was interesting, so I pulled up another SSH connection
and:

```
# dmesg | tail -1
[  703.468505] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not
found at 0x0244003c: 0xa94c instead
[  855.211369] jffs2: Cowardly refusing to erase blocks on filesystem
with no valid JFFS2 nodes
[  855.220100] jffs2: empty_blocks 0, bad_blocks 3, c->nr_blocks 992
```

It appears that there's no JFFS2 filesystem on /dev/mtdblock6. That
makes sense, given:

```
# cat /proc/mtd | grep mtd6
mtd0: 0000c000 00001000 "routerboot"
mtd1: 00001000 00001000 "hard_config"
mtd2: 00001000 00001000 "bios"
mtd3: 00001000 00001000 "soft_config"
mtd4: 00040000 00020000 "booter"
mtd5: 003c0000 00020000 "kernel"
mtd6: 07c00000 00020000 "ubi"
```

It would appear that `mtd6` has UBIFS on it, but:

```
# mount -t ubifs /dev/mtdblock6 /mnt
mount: mounting /dev/mtdblock6 on /mnt/ failed: Invalid argument
```

At this point, I decided to dump `/dev/mtd6` to my laptop, and do some
forensics:

```
# dd if=/dev/mtd6 | ssh ecs@192.168.1.10 dd of=/tmp/mtd6
## blah blah blah fingerprints blah blah blah
ecs@192.168.1.10's password:
253952+0 records in
253952+0 records out
253944+10 records in
253952+0 records out
130023424 bytes (130 MB, 124 MiB) copied, 313.463 s, 415 kB/s
```

Wait! UBI is `ubi`, not `ubifs`:

```
# mount -t ubi /dev/mtdblock6 /mnt
mount: mounting /dev/mtdblock6 on /mnt/ failed: No such device
```

What?!?!

```
# ls -l /dev/mtdblock6
brw-------    1 root     root       31,   6 Jan  1  1970 /dev/mtdblock6
```

By this point, I've installed `ubi_reader` on my laptop and I go back
there to do some diagnostics:

```
$ ubireader_list_files mtd6
UBI Fatal: Less than 2 layout blocks found.
$ less mtd6
## UBI#^A^@^@^@...^E^@^@^B...
## ...
## <FF><FF><FF><FF><FF>...
```

Interesting. It appeared that OpenWRT did not successfully flash, but it
failed consistently. (By this time, I had re-flashed OpenWRT quite a few
times.)

At this point, it was 5:00 in the morning, so I decided to go to sleep.

TODO: how do i get it to work

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% # vim: set ft=markdown :
% preprocessor="markdown -f fencedcode"
# Adventures installing OpenBSD on a PowerBook G4

TL;DR:

1. Download the OpenBSD install ISO
2. If you have a CD and your CD drive works, do that
3. If that doesn't work, flash the ISO onto a USB, and try booting to it
4. If that doesn't work, flash the ISO onto the hard drive
     - Remove the battery
     - Unscrew all 18 screws
     - Take off the memory bay
     - Remove the RAM stick closest to the battery
     - Unplug the ribbon cable beneath that RAM stick
     - Unscrew both Torx T8 screws inside the memory bay
     - Carefully remove the keyboard/plamrest/touchpad
     - Unplug the ribbon cable going over the hard drive
     - Unplug the ribbon cable coming from the hard drive
     - Remove the ribbon cable from the hard drive
     - The hard drive is a 2.5" IDE drive. Connect it to your computer
       and flash the ISO: `dd if=openbsd.iso of=/dev/sdb`
     - Follow these steps in reverse order to put everything back
       together.
     - Boot to OpenFirmware, and run
       `boot hd:,\ofwboot /6.6/macppc/bsd.rd`
5. Install OpenBSD normally. Make sure to put / on the first partition.

I recently found an old computer lying around in my house -- an old
17" PowerBook G4 (A1085, or 5,5). It had stopped working years ago, but
with a new charger, I got it to boot to OS X. However, I wanted to run an
open-source OS on it.

32-bit PowerPC is old enough that practically no-one still supports it.
I ended up choosing OpenBSD, because I managed to boot it before I
managed to boot NetBSD or FreeBSD, and I didn't want to have to deal
with Gentoo's compilation hell on a computer that old.

I downloaded the OpenBSD install ISO, and got to work. The first
challenge was booting to it. The CD drive wasn't working, so I couldn't
boot from there, and for whatever reason, OpenFirmware would hang
whenever I tried to boot from a USB.

So I booted to MacOS (which could read the USB) and used it to copy
the contents of the ISO onto the HFS partition.

It worked... almost. I realized my mistake as soon as I had
repartitioned the hard drive. The sets (gzipped tarballs that are
untarred over the new root) were on the now-destroyed HFS partition. In
addition, I had completely messed up `/dev` earlier (by running `sh
/dev/MAKEDEV all` and running out of space on the ramdisk), so I wasn't
able to copy over sets from my USB. I ended up accidentally killing my
shell without a `/dev/console`, leading to a wedged system.

However, I still had the OpenBSD kernel running, so I was hoping that
maybe, just maybe, if I hot-swapped the hard drive...

So I pulled out a stick of RAM, unplugged the internal keyboard, and it
must have touched some circuit because there was a flash and magic smoke
was leaking out of the logic board. I quickly unplugged it and removed
the battery (thank God for easily removable batteries!).

Note to future self: DO NOT try to take apart a computer while it is
running!

When I turned it on, it no longer chimed on boot, but was otherwise
unharmed.

However, I still had a bit of a problem. I needed to boot to OpenBSD,
but I had no way of booting a CD or USB, and the hard drive was wiped.

Thankfully, a quick `dd if=openbsd.iso of=/dev/sdb` after plugging the
hard drive into my computer worked, and the installer booted just fine
from there: `boot hd:,\ofwboot /6.6/macppc/bsd.rd`.

This time, I made sure that I could access the sets before I
partitioned the hard drive. After putting the ISO in the first partition
of an MBR, I was able to mount `/dev/sd0i`. Success! Now I just had to
finish the installer, and reboot.

Not so fast. The install didn't work, and I wasn't able to debug because
I wasn't able to mount the OpenBSD partition on Linux. So I re-installed
the installer (by this point, I was quite proficient at taking the
PowerBook apart), reinstalled OpenBSD, and got a shell after the install
process, in order to see what was going on.

It went fine, but my custom partitioning had put the kernel in the
second partition (with the first partition being swap), which apparently
confused the bootloader. Once I fixed that, it worked!