7. Tips and tricks

7.1. Redirecting output of the make or patch commands

If you would like logs of what those ` make ' or ` patch ' commands did, you can redirect output to a file. First, find out what shell you're running: ` grep root /etc/passwd ' and look for something like ` /bin/csh '.

If you use sh or bash, (command) 2>&1 | tee (output file) will place a copy of (command) 's output in the file ` (output file) '.

For csh or tcsh, use (command) |& tee (output file)

For rc (Note: you probably do not use rc) it's (command) >[2=1] | tee (output file)

7.2. Conditional kernel install

Other than using floppy disks, there are several methods of testing out a new kernel without touching the old one. Unlike many other Unix flavors, LILO has the ability to boot a kernel from anywhere on the disk (if you have a large (500 MB or above) disk, please read over the LILO documentation on how this may cause problems). So, if you add something similar to image = /usr/src/linux/arch/i386/boot/bzImage label = new_kernel to the end of your LILO configuration file, you can choose to run a newly compiled kernel without touching your old /vmlinuz (after running lilo , of course). The easiest way to tell LILO to boot a new kernel is to press the shift key at bootup time (when it says LILO on the screen, and nothing else), which gives you a prompt. At this point, you can enter ` new_kernel ' to boot the new kernel.

If you wish to keep several different kernel source trees on your system at the same time (this can take up a lot of disk space; be careful), the most common way is to name them /usr/src/linux-x.y.z , where x.y.z is the kernel version. You can then ``select'' a source tree with a symbolic link; for example, ` ln -sf linux-1.2.2 /usr/src/linux ' would make the 1.2.2 tree current. Before creating a symbolic link like this, make certain that the last argument to ln is not a real directory (old symbolic links are fine); the result will not be what you expect.

7.3. Kernel updates

Russell Nelson ( [email protected] ) summarizes the changes in new kernel releases. These are short, and you might like to look at them before an upgrade. They are available with anonymous ftp from "ftp://ftp.emlist.com" in pub/kchanges or through the URL "http://www.crynwr.com/kchanges"