Linux Server Hacks
by Rob Flickenger

The unconfirmed error reports are from readers.  They have not yet been 
approved or disproved by the author or editor and represent solely the
opinion of the reader.

Here's a key to the markup:
        [page-number]: serious technical mistake
        {page-number}: minor technical mistake
        <page-number>: important language/formatting problem
        (page-number): language change or minor formatting problem
        ?page-number?: reader question or request for clarification

This page was updated July 18, 2007.


UNCONFIRMED  errors and comments from readers: 


[vii]  Contributors List;
In the enumeration of contributors, the attributions to various hacks are completely
wrong.

R.D #75 -> #87
K.H #75 -> #89
    #75 -> #90
    #75 -> #91
S.H #44 -> #47
    #53 -> #62
D.L #36 -> #39
C.L #75 -> #77
M.R #36 -> #42
J.V #22 -> #21


(16)  albumize script, line 12;
echo -n `echo $x|cut -f 2- -d '-'`;echo -ne '\000'
should read:
echo -n `echo $x|cut -f 2 -d '-'`;echo -ne '\000'


{23}  3rd paragraph from bottom of page;
This is a little more than a minor technical error, but not a serious error.

The first two sentences of the paragraph are:

  Not much surprise here. at and crontab need root privileges
  in order to change to the user that requested the at job or
  cron job.

The second sentence is false. Both sentences should be replaced
with the following:

  When a user schedules an at or cron job using the at and crontab
  commands, the details of the job are written to a directory that is
  not accessible to non-root users.The commands need root privileges
  in order to allow the user to successfully submit their at or cron
  job.


[42]  Last sentence on page 42;
The final sentence implies that loadlin is used primarily to multiboot between two
systems.  In fact, many serious Linux sysadmins use loadlin as the default boot
loader to avoid the problems with LILO/GRUB.  The final sentence implies otherwise.


[73] 1st paragraph;
Where it says how to restore the boot sector directly from a floppy, I believe 
the suggested command would not only overwrite the intended first 512 bytes on 
the hard drive where the boot sector resides but actually write the full contents 
of the floppy (1.44 MB typically) to the beginning of the hard drive.

That's a whole lot more data than just the boot sector that would be overwritten 
on the hard drive, so it could be disastrous.

Command as seen in my copy of the book:
dd if=/dev/fd0 of=/dev/hda

More appropriate command:
dd if=/dev/fd0 of=/dev/hda bs=512 count=1

(Same as when backing up but with if and of parameters swapped.)



(98)  Last command group on page.;
I think I have found the following typo; instead of:

# ip tunnel add mytun mode ipip remote 240.101.83.2 \
  local 251.4.92.217 ttl 255
# ifconfig tunl0 10.42.2.1

the author intended to write "mytun" instead of "tunl0", namely:

# ip tunnel add mytun mode ipip remote 240.101.83.2 \
  local 251.4.92.217 ttl 255
# ifconfig mytun 10.42.2.1



{121}  4th paragraph;
To run this script from .bashrc or .bash_profile you need to disable it for scp or
non interactive shells.
if [ -s ] ; then
 {
tl&
}

should fix this up..
Otherwuse scp will not work as the header file is too big for scp>>


(175) Hack 83 Restoring a Single Table from Large Mysql dump;
Just a suggestion - it seems like all of my mysql dumps insert backticks all over the place, including the table name, which makes this hack not work. I suggest making the following changes for anyone else having the problem:

Remove the "\b" from the two spots in extract-table script, so this:

#!/usr/bin/perl -wn
BEGIN { $table = shift @ARGV }
print if /^create table $table\b/io .. /^create table (?!$table)\b/io;

becomes this:

#!/usr/bin/perl -wn
BEGIN { $table = shift @ARGV }
print if /^create table $table/io .. /^create table (?!$table)/io;

And when you go to run the command instead of:

zcat /var/spool//mysqldump/randomdb.20020901.gz | extract-table Users > ~/Users.dump

Do this:

zcat /var/spool//mysqldump/randomdb.20020901.gz | extract-table "\`Users\`" > ~/Users.dump

(219) upper right;
the index entry for 'rcg' is mistakenly labelled 'rgc'