The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Author: Ed

Capacitor Plague Up Close

A friend dropped off a dead eMachines Celeron for my next recycling trip. Peering inside, what do my wondering eyes behold but a nasty case of Capacitor Plague!

Herewith, some pix of the victims within the box. Note the bulging tops ready to blow along the pressure-relief grooves, the distinct tilt caused by the bulging bottom plug, and the right-hand cap near the power supply on countdown for launch!

Near DIMM slots

Near PCI slots

Power supply caps with bottom leakage

More background on the plague is there.

I must build an ESR tester one of these days…

2009-04-26
Backup with Rsnapshot
Now that our low-budget file server (a stock Dell Inspiron 531S desktop with an additional 500 GB SATA drive) is up & running Xubuntu 8.10, it’s time to get rsnapshot working again.

All our data files live on the server, so the backup routine need not handle any of the usual /home stuff on our desktop boxes. Rebuilding a dead box is a nuisance, but they’re all pretty much the same and it’s less of a nuisance not worrying about rare failures… haven’t had any failures in many years; they get replaced before they die.

The backup files go to an external 500 GB USB drive, which is not protection against a catastrophe in the basement. Mostly, this guards against finger fumbles; the external drive gets dumped to another hard drive in the fireproof safe more-or-less monthly.

So. To begin…

Install rsnapshot, which will also drag in ssh, the metapackage around the client & server sides of openssh. The server side is already installed so I can sign in using public-key authentication.

Set /etc/rsnapshot.conf thusly (comments snipped out):
```
snapshot_root   /mnt/backup/snapshots
no_create_root  1
cmd_cp          /bin/cp
cmd_rm          /bin/rm
cmd_rsync       /usr/bin/rsync
cmd_ssh /usr/bin/ssh
cmd_logger      /usr/bin/logger
cmd_du          /usr/bin/du
cmd_rsnapshot_diff      /usr/bin/rsnapshot-diff
#interval       hourly  6
interval        daily   30
#interval       weekly  4
interval        monthly 12
#interval       yearly  1
logfile /var/log/rsnapshot
du_args -csh
backup  /mnt/userfiles/         oyster/
backup  /mnt/bulkdata/          oyster/
backup  /mnt/music/             oyster/
backup  /mnt/diskimages/        oyster/
```
Basically, that creates a month of daily backups, plus monthly backups for a year. Haven’t ever gotten to a yearly backup, but you get the idea.

The no-create-root option prevents horrible things from happening if the USB drive wakes up dead and doesn’t mount; you don’t want to back up the drives to the /mnt/bulkdata mount point. The USB drive mounts using a UUID entry in /etc/fstab, as described there.

Create a pair of scripts in /root to mount the USB drive, do the backup, unmount it, and shut down the system:

rsnapshot.daily
```
#!/bin/sh
logger "Mounting USB drive"
mount /mnt/backup
logger "Starting backup"
/usr/bin/rsnapshot daily
logger "Unmounting USB drive"
umount /mnt/backup
logger "Power off"
shutdown -P now
logger "Done!"
```
rsnapshot.monthly
```
#!/bin/sh
mount /mnt/backup
/usr/bin/rsnapshot monthly
umount /mnt/backup
shutdown -P now
```
Note: the rsnapshot executable has moved from /usr/local/bin in Ubuntu 7.10 to /usr/bin in 8.10.

You could be more clever than that, but, eh, they’re simple & easy.

The Inspiron 531S 1.0.13 BIOS now powers off dependably with the 2.6.27-14-generic kernel in 8.10, a pleasant change from the 1.0.12 BIOS and the 2.6.22-16-generic kernel used in 7.10. That means the shutdown commands work and I can shave 25% off the server’s power bill. Not that it’s very big to begin with, but every little bit helps.

Set up /etc/crontab to run the backups (and sync the system clock with reality, for the reasons described there):
```
10 23	1 * *	root	/root/rsnapshot.monthly
30 23	* * *	root	/root/rsnapshot.daily
#
00 01	* * *	root	ntpdate north-america.pool.ntp.org
```
And that’s it.

Memo to Self: add e2fsck to the monthly backup routine and move it an hour earlier.
2009-04-25

Ubuntu 8.10 Server Setup: Samba

We need Samba for the Token Windows Laptop and the CNC box on the milling machine which also runs TurboTax during that season of the year. Despite having done this many times before, it never works right until, suddenly, without warning, everything works. It’s a permission thing, I think.

To get SWAT running, check there, which boils down to:

sudo chmod g+w /etc/samba/smb.conf
sudo chgrp adm /etc/samba/smb.conf

Put this in /etc/xinetd.d/swat:

... comments snipped ...
service swat
{
        port    = 901
        socket_type     = stream
        wait    = no
###     only_from = localhost
        user    = <<your adm-enabled userid>>
        server  = /usr/sbin/swat
        log_on_failure  += USERID
        disable = no
}

Then use sudo smbpasswd -a -e <> to set up the allowed users and get their passwords aligned. I use the same userids and paswords on all the boxes, which is terrible security.

Whenever you change anything, use sudo /etc/init.d/samba restart to make sure Samba gets the message.

Use SWAT to set up all the shares. This is what the config file looked like after the damn thing finally started working:

# Samba config file created using SWAT
... snippage ...

[global]
	workgroup = whatever-you-use
	server string = %h server (Samba, Ubuntu)
	map to guest = Bad User
	obey pam restrictions = Yes
	passdb backend = tdbsam
	pam password change = Yes
	passwd program = /usr/bin/passwd %u
	passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
	unix password sync = Yes
	syslog = 0
	log file = /var/log/samba/log.%m
	max log size = 1000
	dns proxy = No
	usershare allow guests = No
	panic action = /usr/share/samba/panic-action %d

[printers]
	comment = All Printers
	path = /var/spool/samba
	create mask = 0700
	browseable = Yes
	printable = Yes
	writeable = Yes

[print$]
	comment = Printer Drivers
	path = /var/lib/samba/printers

[Bulkdata]
	comment = Assorted useful files
	path = /mnt/bulkdata
	read only = No

... likewise for other file shares ...

Actually, you don’t have to share the printers with Samba. Better to use CUPs directly. Just tell Windows to “Connect to a printer on the Internet or on a home or office network”, then fill in something like:

http://oyster:631/printers/R380_TP

And that’ll work even better.

2009-04-24

Ubuntu 8.10 Server Setup: Tweaks & Glitches
Having just bumped the basement file server from Kubuntu 7.10 to Xubuntu 8.10, a few notes are in order…

The general idea was to saw an existing 20 GB partition in half, maintain the existing 7.10 installation, and install 8.10 in the liberated part. The overview:
- partimage — back up the 7.10 installation in sda6 and the data in sda7
- resize2fs -p /dev/sda6 5G — squish the filesystem down
- partimage — save the squished filesystem
- cfdisk — delete sda6 and create a pair of 10 GB partitions sda6 and sda7
- partimage — restore the squished filesystem to sda6
- e2fsck -fv /dev/sda6 — prep it for resizing
- resize2fs -p /dev/sda6 — expand to fill entire partition
- tweak /etc/fstab to reflect the fact that sda7 has become sda8
- reboot and shazam 7.10 started up just fine
Then install 8.10 in sda7 and configure from there, using the 7.10 installation as a reference to help remember what’s needed.

The only complication was that the Ubuntu 8.10 mini-ISO install enumerated the USB backup drive as sda, so things got a bit weird; evidently, the USB drive now has the grub MBR. Unplugging that drive, then deploying a bit of grub fu from SystemRescueCD fixed that up:
- find /boot/grub/stage1 — appears in (hd0,5) and (hd0,6), thus sda6 & sda7
- root (hd0,6)
- setup (hd0)
Then apply the relevant installation info from the series starting there, omitting all the user apps and foo-foos that won’t be needed on the basement box.

Add useful server programs:
- nfs-kernel-server
- xinetd
- swat
There’s an authorization bug that may kill local login and sudo, as documented there, triggered when you configure CUPS printers (among other causes). The quick-and-dirty solution seems to be:
- boot in recovery mode
- remove samba*
- install samba
- install xubuntu-desktop
It’s worth noting that I’d just finished configuring ssh for public-key logins, so I could get into the box from my Comfy Chair upstairs, but I couldn’t reconfigure anything because sudo segfaulted.

Create mountpoints, then set up /etc/fstab to automount the various partitions:
```
/dev/sda8 /mnt/music		ext3	defaults,noatime,auto,rw,nodev,noexec,nosuid 0 0
/dev/sdb1 /mnt/bulkdata		ext3	defaults,noatime,auto,rw,nodev,noexec,nosuid 0 0
/dev/sdb2 /mnt/diskimages	ext3	defaults,noatime,auto,rw,nodev,noexec,nosuid 0 0
/dev/sdb3 /mnt/userfiles	ext3	defaults,noatime,auto,rw,nodev,noexec,nosuid 0 0
UUID=069e50dc-1994-47d2-9c7e-0b5179a89041 /mnt/backup ext2 defaults,noatime,noauto,nodev,noexec,nosuid 0 0
```
It would be more sensible to use UUIDs for those partitions, but that stuff hasn’t broken yet. If the USB backup drive enumerates as sda again, then I’ll be forced to tweak it.

Add stanzas like this to /etc/exports:
```
/mnt/bulkdata *(rw,async,subtree_check,root_squash,no_all_squash)
```
That gets the files served to the other boxes.

Install Turboprint and tweak the printer drivers accordingly.
2009-04-23
Zero-dollar Power Screwdriver Repair

I’m in the midst of cleaning up the shop after a winter of avoiding the too-cold basement. The best way I’ve found to pull this off is to pick up each object, do whatever’s needed to put it away, and move to the next object. Trying to be clever leads to paralysis, so I devote a few days to fixing up gadgets and putting tools back in their places. After a while, it gets to be rather soothing.

Broken wire in power screwdriver

Some months ago I snagged a power screwdriver from a discard pile; while it didn’t work, un-bending the battery pack connector solved that. It runs from a quartet of AA cells, which means I can use alkalines and it’ll always be ready to go. It’s not a high-torque unit, so I’m using it for case screws and similar easy tasks.

But it quickly became intermittent and finally would turn only clockwise. Onto the to-do heap it went…

Power screwdrivers consist of a battery, a motor with a planetary gear reduction transmission, and a cross-wired DPDT switch in between. Not much can go wrong and, if it turns at all, most likely the problem has something to do with the switch or wiring.

Opened it up, pulled out the motor, and, lo and behold, one of the wires has broken off the switch. As nearly as I can tell, pushing the switch that-a-way forced the solder tab down on the wire and made the connection, pushing it the other way pulled the tab off the wire.

While I had the hood up, I replaced the wires with slightly thicker and longer ones. Soldered everything back together, mushed the grease blobs back into the planetary gearing, and it works like a champ…

Now, fairly obviously, there’s absolutely no economic sense to this sort of thing, given that the driver probably cost under ten bucks, but I just can’t stand to see a perfectly good gadget wind up in the trash.

I’d love to do this sort of thing for a living, if only I could figure out how to avoid going broke while doing so. Maybe I can get me some of that my economic stimulus money that’s sloshing around these days?

2009-04-22
Bullet Hole in Plate Glass

Pellet gun hole in plate glass

Found this hole in the plate glass window of a church.

The conchoidal fracture pattern is characteristic of a bullet impact at more-or-less right angles to the pane. I suppose, based on the very small entry hole and no damage to the opposite wall, that it was something like a BB gun at close range, rather than a 0.22-cal handgun or rifle far away.

Somehow, you just know the lunkheads doing this sort of thing have never repaired a window themselves… when you’re a constructor, you just don’t go around destroying things.

But maybe that attitude marks me as a fuddy-duddy.

2009-04-21
XFCE Keyboard Mapping: Random Jots
The multimedia keyboard on this box doesn’t work, which likely has something to do with the fact that I’m running separate X sessions on two monitors. I described what does work on my laptop there.

Here are some random & incomplete notes, with no good outcome…

Key and keyboard definitions are in /usr/share/X11/xkb/keycodes with:
- xfree86 mapping the symbolic name (as in <I1E>) to key number 158
- inet mapping from XF86AudioRaiseVolume to symbolic name
The Microsoft Comfort Curve Keyboard 2000 V1.0 (don’t you love how they name things?) seems to be a subset of the microsoftprousb keyboard definition.

Manually assigning a key works like this:
```
xfconf-query -c xfce4-keyboard-shortcuts \
  -p /commands/custom/XF85AudioRaiseVolume \
  -t string
  -n
  --set="amixer -c 0 sset Master 10%+"
```
Use xev to find key numbers, which turn out to be more or less common values (contrary to what I initially thought)…
- Back = 234 I6A
- Forward = 233 I69
- Vol down = 174 I2E
- Mute = 160 I20
- Vol up = 176 I30
- Play/Pause = 162 I22
- Home = 178 I32 XFree86HomePage
- Search = 299 I65 XFree86Search
- Email = 236 I6C XFree86Mail
- Calculator = 161 I21 XFree86Calculator
The first two keys are defined in nav_common and the rest are in media_common, with the combination in, of course, media_nav_common.

But none of this actually works.
2009-04-20

Author: Ed

Capacitor Plague Up Close

Backup with Rsnapshot

Ubuntu 8.10 Server Setup: Samba

Ubuntu 8.10 Server Setup: Tweaks & Glitches

Zero-dollar Power Screwdriver Repair

Bullet Hole in Plate Glass

XFCE Keyboard Mapping: Random Jots