Things to Remember

• Find your IP address using ipconfig.
• To edit Windows startup, run msconfig and uncheck anything you don't want in the tray.
• During installation, never name a Windows PC with any identifier you might want to use later.
• Windows will not boot from a partition formatted by mkdosfs.
• FAT 32 supports up to 2 TB, but XP will only format up to 32GB.
• Western Digital software will copy a FAT 32 filesystem to a larger partition if it's <= 32 GB; install and run from Windows (it's faster).

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• Western Digital drives want to be Cable Select if they are alone, not the Master.

  For IDE drives, Cable Select is no jumpers; Master is the middle jumper, and Slave is the jumper to the right of the Master (from the back).

• When configuring a wireless device, turn broadcast SSID off, use WPA (not WEP) and MAC address filtering.

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• When the DVD drive repeatedly reports I/O errors while reading just-burned discs, reboot Linux; the discs will probably have to be re-burned, but they should now burn "true" (last noticed on 2.6.16 kernels).
• To access a Mac hard drive, you need to enable EFI and GUID in the kernel.
• If users cannot write to the root of a mounted filesystem, chown the mount point while the filesystem is mounted.
• If you get a lot of bash "command not found" errors, check $PATH, look at the first directory (or two), fix your problem and then hash -r.
• Check the status files in spool directories for hints about "mystery" errors.
• If you have loops in printcap and the file looks OK, clear the print queue and restart lprng.
• Some browsers (Seamonkey in particular) will follow links to "file://" only if the referring page was loaded from a local file.
• To rotate the system log file by hand, mv sys.log sys.log.old, touch sys.log, sysklogd restart. If rotating apache logs, apachectl restart.
• To increase JRE heap space, run /opt/jdk/jdk/bin/ControlPanel, choose Java tab, View Java Applet Runtime Settings, and in the "Java Runtime Parameters" area, add -Xms64M -Xmx512M.
• With OpenJDK 1.7, it helps to add /opt/jdk/jre/bin to your path. itweb-settings (replaces ControlPanel) and policytool are in there.
• If you can't open local files from java applets in your web browser, and you are reasonably confident in the security of their location, you can use the policytool to edit .icedtea/secsurity/java.policy. Add the codebase "file://(fully qualified directory name)/-" with AllPermission. Remember to save the edit.
• If your IP address changes, you will probably have to restart Postfix in order to receive mail.
• Apache returns 200 on a cgi program but no output (or the cgi source) appears; make sure the cgi module loaded.
• Gimp layer mode operations:
  • lighten only: max (lower, upper)
  • screen: 255 - (255 - upper) * (255 - lower) / 255
  • dodge: 256 * lower / (256 - upper)
  • addition: min (upper + lower, 255)
  • darken only: min (lower, upper)
  • multiply: upper * lower / 255
  • burn: 255 - 256 * (255 - lower) / (upper + 1)
  • overlay/soft light: lower * (lower + 256/255 * (255 - lower) * upper) / 255
  • hard light: if upper > 128 then 255 + (2 * upper - 513) * (255 - lower) / 256; else upper * lower / 128
  • difference: | lower - upper |
  • subtract: max (lower - upper, 0)
  • grain extract: lower - upper + 128
  • grain merge: lower + upper - 128
  • divide: 256 * lower / (upper + 1)
  • hue: If upper is B+W, then lower; else H of upper and SV of lower
  • saturation: S of upper and HV of lower
  • color: HS of upper and V of lower
  • value: V of upper and HS of lower
• If you grep a file which should be plain text and grep complains about it being a binary file, it probably got clobbered during a power failure. This is often going to be the system log file. Open it with emacs, identify the line with the garbage in it, and use an in-place sed to remove that line.
• If alsamixer doesn't show the correct mixer settings, you probably don't have the correct codec module loaded. Unload the module for your card, load the correct codec module, and then reload the card module.

©2017, Kenneth R. Koehler. All Rights Reserved. This document may be freely reproduced provided that this copyright notice is included.

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