MacOSX sysctl.conf issue and resolution

Yesterday I decided to tweak my MacOSX (10.3.9) to supposedly speed up network transfers on my G5. I created /etc/sysctl.conf file and entered configuration based on some tip found on macoshints.com website to speed up Samba transfers. Not that I am unhappy with my setup, it's just I like to try new things and unleash hidden powers!

net.inet.tcp.mssdflt=1460
net.inet.tcp.sendspace=262144
net.inet.tcp.recvspace=262144
net.inet.udp.recvspace=74848
net.inet.udp.maxdgram=65535
net.inet.tcp.rfc1323=1
net.inet.tcp.newreno=1
net.inet.tcp.always_keepalive=1
net.inet.tcp.keepidle=3600
net.inet.tcp.keepintvl=150
net.inet.tcp.slowstart_flightsize=4
net.inet.tcp.strict_rfc1948=1
net.inet.tcp.delayed_ack=1

Indeed on MacOS if that /etc/sysctl.conf file is missing, since it's BSD distribution it's still looked at and picked up by /etc/rc bootup script, which sets all its data values using sysctl. Very powerful. So curious of this finding and excited by possible gain of speed, I went on and rebooted..... That's when the problem arised..... The system got sluggggiiiissssshhhhhhh. Started with network file server (NFS) load, till login screen ... that I never saw.....

Of course I had no bootup CD at hand, to undo my change. So much like me! I knew I had to to boot in Single User mode but I couldn't remember the bootup keys combination. So I felpt stuck, despaired, and angry at myself.

Lucky me I had another computer plugged in my router, to hook up to the internet! Kissed my Lucky Star... I could now boot and get the root prompt. I saw my /etc/sysctl.conf file, but there was no way to either delete it, or edit it! Sigh! The system complained that the system file was read only, but I was root with root privileges! A config file held by a process maybe? never heard of that before! It took me time, anger and more reading to figure that I needed to manually mount the volume in read/write mode. What I did. That was it! I could delete the culprit and reboot at blazing speed.

So what needed to happen:
- reboot computer in single user mode (press Command-s while booting)
- mount main volume in read/write mode (mount -uw /)
- remove /etc/sysctl.conf file (rm /etc/sysctl.conf)
- reboot

Here are the actions I felt at that time I should have taken before:
- print out / learn bootup commands
- burn a MACOSX bootup CD in case I need to jumpstart my G5 externally
- not simply change configurations unless really necessary and well understood, or a backup plan in place
- learn more about MacOSX bootup sequence. There's an excellent page on that.
- learn more about tcp/ip / kernel intricacies

Simple precautions. Computers are toys to toy with. But when they break we realize they are more than that. Now I feel more confident and will probably play around some more, once I feel comfortable.