Ubuntu Linux
I noticed today that the FreeBSD ZFS pool that I created on my laptop SSD was not configured for TRIM. TRIM enables the SSD to recover space from previously written to blocks that have since had files deleted. This can help maintain performance of the SSD as it fills with data.
My pool is called zroot, so the command to check the value of the TRIM setting is:
$ zpool get autotrim zroot
The command to switch on automatic TRIM is:
$ zpool set autotrim=on zroot
I have an old PC with what appears to be a broken implementation of USB. I cannot obtain a BIOS update and there is no BIOS setting to switch off USB either. Very old Linux distributions would run on this PC, but only on those with USB support as loadable modules. For later kernels with direct USB support I would get continuous error messages to the console.
After spending some time Googling, I found this useful post
For Ubuntu 10.04 LTS I used the advice to create rules to deactivate USB entirely on this host. The first file that I created was /etc/udev/rules.d/20-disable-ehci.rules which contained the following code:-
ACTION=="add", SUBSYSTEM=="pci", DRIVER=="ehci_hcd", \ RUN+="/bin/sh -c 'echo -n %k > %S%p/driver/unbind'"
When I rebooted the PC, it disabled one of the troublesome USB hubs but I was still getting error messages for another but much more frequently now. I experimented by creating a similar file to deactivate ohci but this didn’t do anything. I tried again with uhci and that worked, USB completely disabled.
/etc/udev/rules.d/30-disable-uhci.rules
ACTION=="add", SUBSYSTEM=="pci", DRIVER=="uhci_hcd", \ RUN+="/bin/sh -c 'echo -n %k > %S%p/driver/unbind'"
So if you have two or more USB hubs throwing enumeration errors, try disabling both EHCI and UHCI, it worked for me.
Obviously, if you have any USB devices that you need to use with this host, forget it. You will need a new motherboard.
During our recent house move I found my old and dusty PowerMac 8500/180 while we were packing up the contents of my garage. It had been placed on the bottom shelf of my car spares shelving for a time when I could either make a VGA adapter cable or acquire another old Mac monitor to replace the one that died. That was back in 2004, and as time passed by storage crates piled up in front of it and it was soon forgotten.
A long time ago I was a NetWare specialist and I had a variety of non intel computers in my private lab that I used for working on interoperability projects. Many of my customers had a small number of Macintosh computers in their organisations and I acquired my 8500 second hand when one of them switched to Windows a year after purchase.
I can’t say that I was a Mac specialist in any sense. My interest was purely interoperability with NetWare, Unix and other corporate host based systems. I tinkered a lot with Applescript and had a lot of fun with my 8500. However, I didn’t like the fact that Apple built the machine to be supported only by their own engineers. There weren’t any manuals for DIY upgrades as you were supposed to take the 8500 to an Apple technician for things like RAM upgrades. I soon learned that Apple products were all about lock-in. I found this aspect of Mac ownership distasteful to the point that I probably wouldn’t buy another Mac again even though I liked my 8500.
So time moves on. It’s 2011 and the 8500 is sitting in my new garage. I don’t want to leave it there to deteriorate for another seven years so I dust it off and bring it into the house to see if it still works. I still don’t have a Mac to VGA adapter but the 8500 has TV output. I connect it to my 42″ LCD TV using an RCA composite TV cable (Yellow-Red-White). After plugging the onboard Ethernet into a live switch on my LAN, and completing the remaining connections for power, keyboard and mouse, the Mac powers up and the familiar chime is heard all over the house through the TV speakers.
I was really pleased that it still worked after all this time. I found some old QuickTime video clips of the kids when they were younger in a folder on the hard drive. I guess when the monitor died I didn’t have any way of accessing my files to save them back then. I set about copying off the files I wanted to keep by uploading to my file storage using Internet Explorer 5 that was still on the Mac and then I began depersonalising the machine ready for disposal. While I was dragging files to the Wastebasket, I started to think that maybe I could use this machine with Ubuntu or Debian as part of my CCTV system. After all, it had on-board analogue video capture that was too fast for any hard-drives produced at the time. Perhaps someone had developed the necessary drivers for V4L2. I didn’t stop too check first, I downloaded a copy of Debian 6.0.2.1 as I thought this would work with an OldWorld Mac and set about installing it.
Oh dear. It appears that a Mac monitor is necessary to install Linux as the TV display doesn’t work when Bootx is used to start the Debian installation. The next problem I have is that I don’t have any Mac OS installation media any more to resize the Apple partitions. A house flood in 2009 saw a lot of my stuff go in the rubbish skip never to be replaced. All my obsolete computer manuals, books and software were either destroyed or water damaged and I’m fairly certain that my Mac OS 8 install disks went in the same skip. I pack up for the day and think about how I can resolve this problem overnight.
The following morning I have an idea. Another old PC that was similarly shelved had a Matrox Mystique card inside. This had a Mac display port so I thought It may have originally been Mac compatible. I relieve the PC of the Matrox card and install it in the Mac with a USB 2.0 + FireWire PCI card. A 60GB portable hard drive is connected to the USB port and a flat panel LCD display to the Mystique’s VGA port before rebooting the Mac.
Mac OS 8.1 starts up and is displayed on the TV. I pop in the Debian CD-ROM and copy the installation kernel and ramdrive to the Linux Kernel folder in the Mac System Folder and configure Bootx to use them. Starting Debian from Bootx the TV display loses its signal and shows the default blue screen. The LCD monitor is now showing a familiar penguin and I can see that Linux is booting and in the hardware detection phase.
I manage to successfully create a Linux partition and swap partition on the USB hard drive but the installation always stalls at some point when unpacking an archive on the CD-ROM. Looking at the logs, the installation is almost there, but the live kernel has not been created in /boot and it’s not good enough to even try building it by hand. Disappointed, I abandon this project yet again to think about it overnight.
Next morning I have an idea. I downloaded the last Ubuntu distribution that officially supported the PowerPC architecture. The Alternate install image for Ubuntu 6.06 LTS PPC seemed most appropriate considering that my Mac has only 96MB of RAM. I replaced the Bootx kernel and ramdrive from this CD and recommenced installation.
Success! The installation is plodding along well. I let it run on its own all day, coming back now and again to check progress and answer any waiting prompts. When it finished I rebooted and logged in to Ubuntu at 640×480 resolution. I started up the System Monitor and had a played a game of Solitaire before tweaking a few settings one by one.
Disaster strikes! Somewhere during the installation I failed to notice that the Mac didn’t have a network connection when running Linux. My Ethernet switch indicates that the on-board MACE (Mac Ethernet) is present at 10Mbps but it won’t DHCP or accept a static IP address. I try installing an Intel E100B PCI adapter and it’s the same. Booting back into Mac OS 8.1 there’s no network now. I just can’t get it to connect. I tried zapping the PRAM and NV but I couldn’t check the OpenFirmware on the serial port as I don’t have a Mac serial lead anymore.
Without a network connection, this 8500 is useless to me. So, the final enjoyment I got from my Mac was using Ubuntu 6.06 on it. I’m not sure if it was any quicker than Mac OS 8.1 as I only have 96MB of RAM installed but it was an interesting exercise on how to get Ubuntu running on a Mac without the Mac OS install discs.
Sadly, I don’t have a use for a Mac that cannot connect to my LAN. I can’t explain why the MACE shows a connection on my switch but refuses to load TCP/IP. Maybe the logic board got a static zap when I was plugging in PCI boards. Maybe I have pressed some key sequence that has deactivated the board in OpenFirmware without my knowledge. If I don’t find a way of getting the onboard Ethernet running again under Mac OS this Mac will be going to the recycling centre very soon.
I have been experimenting with Zoneminder recently, using the pre-built package for Ubuntu 11.04. I couldn’t get the package to work properly but found some very useful instructions in the Zoneminder Wiki that made it work.
When I finish the installation I will put this into an install script.
I found this really simple way of finding the installed BIOS version on an Ubuntu PC without having to reboot. Simply execute the following command in a terminal session and scroll through the output until you find the BIOS section.
sudo dmidecode -s bios-version
For more system information, just scroll through the output until you find what you need.
sudo dmidecode | more
Update August 2012
I have successfully installed Lubuntu 10.04 on an old Toshiba Tecra 8000 (Pentium Mobile 233 with 256MB of RAM) and found that this trick to find the BIOS version did not work. The BIOS in my old Tecra is older than 1999 and doesn’t have the Desktop Management Interface present.
Do you get two welcome messages when logging in to your Ubuntu 10.10 host? I have experienced it on hosts upgraded from 10.04 and on freshly built hosts from the downloaded CD-ROM images. The problem can be easily fixed using…
sudo rm /etc/motd.tail
If you are still using password based login for SSH, consider using key based logins instead. It is very easy to set up, convenient to use and secure. If you also use PuTTY on a Windows PC you can use Pageant as the automatic authentication agent.
The command ‘last‘ lists the times and dates of successful logins. The command ‘lastb‘ lists unsuccessful attempts. I found that both unnecessarily had public read access on most of my Ubuntu servers.
Two log files provide the data used by last and lastb. Both can be secured by changing the permission to 660.
sudo ls -l /var/log/?tmp
sudo chmod 660 /var/log/?tmp
sudo ls -l /var/log/?tmp
Afterwards, to list successful logins, use:-
sudo last
To list unsuccessful logins, use:-
sudo lastb
Whether the ftp daemon is in use or not on a Linux host, it’s a good idea to restrict the system user accounts from using it. Any user ID that is in /etc/passwd that is not permitted to use ftp should be copied to /etc/ftpusers. The following commands for Ubuntu create the file with a list of all users.
sudo awk -F”:” ‘{ print $1 }’ /etc/passwd | sort > ~/ftpusers
Edit the resulting ~/ftpusers to remove the IDs that are allowed to use ftp.
sudo nano ~/ftpusers
Then move the file from your home directory to /etc.
sudo mv ~/ftpusers /etc
The old Dell laptop that I use for packet sniffing was in need of a rebuild after I had been experimenting with Zabbix. In hindsight, I shouldn’t have used the laptop that has become my network toolkit. I had well and truly messed it up and I was desperate to get it operational again.
Ubuntu 10.10 had recently been released and I had already downloaded the ISO images overnight. With a freshly burned CDR in my hand, I set about installing the new version. This laptop is primarily a network analysis tool so Wireshark was naturally the first application to be installed. It wasn’t long before I found that 10.10 has the same missing interface problem that I had experienced with 10.04. “No problem” I thought. “I will just use the fix that I found for 10.04“. Well, that didn’t work either. I left it for a day to have a think, and came back to it with a solution that I found on Launchpad. The fix is as follows.
In a terminal session, execute these commands:-
sudo addgroup –quiet –system wireshark
sudo chown root:wireshark /usr/bin/dumpcap
sudo setcap cap_net_raw,cap_net_admin=eip /usr/bin/dumpcap
Using your favourite text editor, add your user id to the wireshark group in /etc/group or use usermod instead:-
sudo usermod -a -G wireshark vince
Reconfigure the Wireshark Common package and answer ‘Yes’ to the question ‘Should non-superusers be able to capture packets?’ :-
sudo dpkg-reconfigure wireshark-common
Reboot, login and test Wireshark. The missing interfaces should be present now.
I had an unlimited download account with my previous Internet Service Provider and I never worried about what time of day I would download a CD-ROM ISO or system update. However, since changing to PlusNet I am now on a 60GB per month download limit as unlimited accounts are now a thing of the past. Now 60GB may seem a generous allowance, but in reality upload traffic also has to come of the allowance. With everyone in my household being a heavy internet user, 60GB a month is often not enough.
Fortunately for PlusNet customers, any internet use after midnight and before 8am does not come out of their monthly allowance. So to take advantage of this overnight benefit I have been adjusting the times that our computers perform their automated updates.
For all of our Microsoft Windows machines this is easily done in Windows update. Just set the time that updates should commence. In my case, I have set our fastest Windows PC to update at 7:05am, and all the others at 7:10am. My Son’s PC is woken up at 7:00am by it’s system BIOS and the updates it pulls down are cached on my Squid Proxy Server. The other Windows PCs collect their updates when they are switched on and most of the files are served from the proxy cache.
For all my Ubuntu hosts I have disabled the built-in automatic update feature and I use a CRON job that I can control instead. To do this, open a terminal session and run the CRONtab editor with the following command:-
sudo crontab -e
When the editor launches, paste the following line into the file and save your work. That’s it.
5 0 * * * (/usr/bin/aptitude -y update && /usr/bin/aptitude -y safe-upgrade) 2>&1 >> /var/log/automatic-update.log
Cron will perform a safe upgrade at 5 minutes past midnight. As I am using a Squid proxy to cache Ubuntu updates, I set my other machines to start their update 5 minutes later by changing the ‘5’ for ’10’ in the crontab line.
For a more detailed explanation of how this crontab command is constructed visit Kevin van Zonneveld’s blog
