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Hints and Tips For SysOps Running Linux
By Janis Kracht 1:261/38 (janis@filegate.net)

 

 

Though many of us have converted our Operating Systems, bbs software, echomail tossers, and mailers to new ones many times, changing one's setup to run under Linux can be perhaps more challenging than anything else ever experienced <smile>.

Hopefully this article will be of some help if you have just switched to Linux, or if you are about to do so. I'll show you some comparisons between DOS and Linux so that you can see that Linux isn't as foreign as it might at first seem, and then I'll provide some scripts that I've written to perform various functions on my bbs system. Lastly, I'll also include a few notes regarding some things you should _make sure_ do when you install linux. Security under Linux is a very large topic however, so I will cover that in more detail in a later article.
First off, let's look at some commands that you might commonly use under DOS, and their Linux counterparts. As you'll see, there are some commands that do not have an equivalent under DOS (i.e., I'm not counting DOS GNU utilities, etc. since these are not generally part of the standard DOS distribution.)
 

Tip: It would probably be a good idea to type 'man command', or 'info command', or 'command --help' without the quotes to see all the options of these Linux commands.
DOS Linux Description
command.com
n/a
n/a
n/a
n/a
sh
bash
perl
awk
chsh
Simplistic command interpreter
Advanced command interpreter
Interpreter for perl scripts
Interpreter for awk scripts
Change shell

 
 
Directory Management

 
DOS Linux Description
dir
dir
dir /w
cd
rd
md
deltree /Y
n/a
ls -1
dir
ls
cd
rmdir
mkdir
rm -rf
pwd
Long format directory
Long format directory
Wide directory format
Change directory
Remove a directory
Make a directory
Recursively delete a directory tree
Directory path
Some Linux examples:
ls -d .*                  Show only "." directories.  (these are
                          often configuration files, etc. for
                          various programs).  The -d indicates that
                          only the directory name should be shown,
                          not the contents.
ls -ltr                   Sort by date, reverse order.
ls --color=auto           Turn on color for file types in directory
                          list
ls -1                     -1 (one) shows file names in column list
                          with no other info
Example of ls -1:
[janis@filegate]$ ls -1
absHOWTO.zip
games.zip
Mail/
newfiles/
[janis@filegate]$ _
 
 
 
 
 
File Management
DOS Linux Description
copy
move
touch
del
type
n/a
n/a
attrib
rawrite
subst?
cp
mv
touch
rm -f
cat
chown
chgrp
chmod
dd
ln
Copy a file
Move a file
Set timestamp on a file
Delete a file
Print file to the screen
Change ownership of a file
Change group ownership of a file
Change access permissions of a file
Write directly to a device
Create a link to a file


Some Linux examples:


mv firstdoc.txt seconddoc.txt                    rename firstdoc.txt

mv /janis/*.txt     /afiles                               move *.txt to directory /afiles.
 

Tip: When moving groups of files with the same filename, such as mv *.tic *.bad, you must specify a different directory. To move files such as *.bad to *.tic, you can use the script in this article, mvbad2tic.

Aliases

You can tell the system to use aliases of the commands you use.


Enter these in your /etc/profile to make them global or ~/.bash_profile to make them local.
 

alias del='rm'
alias copy='cp'
alias move='mv'
alias ren='mv'
alias type='cat'
alias rd='rmdir'
alias md='mkdir'
alias help='man'


You can also enter them on the command line, just for that session. If you type:

alias md='mkdir'

you can then use md instead of mkdir.
 
 
 

Searching and Sorting
DOS Linux Description
find
dir /s
n/a
n/a
sort
n/a
grep
find
locate
updatedb
sort
tr
Search for a string in a text file
Search for a file
Search for a file via a database
Create searchable databas of files
Sort a file
Translate, squeeze, and or delete characters
from standard input.
Some Linux examples:

 
Tip: ctime option in the find command will show status of a file that was last changed n*24 hours ago.   daystart measure times (for -ctime, and other options for find) from the beginning of today rather than from 24 hours ago.
An example of find:

[bbs@filegate /home/bbs]$ find /home/ftp/pub -daystart -ctime 00
/home/ftp/pub/gamesnet/g_cons/descript.ion
/home/ftp/pub/gamesnet/g_cons/CC0CPC10.ZIP
/home/ftp/pub/gamesnet/g_cons/C19WKWK7.ZIP
/home/ftp/pub/gamesnet/g_cons/C50STR14.ZIP
/home/ftp/pub/gamesnet/g_cons/CABPRT20.ZIP
/home/ftp/pub/gamesnet/g_cons/CBCGRB02.ZIP
[bbs@filegate /home/bbs]$ _




Disk Management
DOS Linux Description
fdisk
format
format
chkdsk
n/a
n/a
n/a
n/a
chkdsk
dir /s
fdisk
mke2fs
fdformat
e2fsck
swapon
swapoff
mount
umount
df
du
Modify the partition table
Create a file system on a partition
Format a floppy disk
Test a file system for errors
Turn on a swap partition
Turn off a swap partition
Attach a file system to the root file system
Detach a file system from the root file system
View amount of disk space available
View amount of disk space used by a directory recursively


Some examples of Linux commands:

The mount command with no parameters specified shows you the devices currently mounted.
 
[bbs@filegate ~]$ mount
/dev/hda1 on / type ext2 (rw)
none on /proc type proc (rw)
/dev/hdb1 on /export type ext2 (rw)
none on /dev/pts type devpts (rw,mode=0622)
[bbs@filegate ~]$
 




Getting Help with Commands:
DOS Linux Description
help
n/a
n/a
n/a
n/a
man
apropos
whatis
makewhatis
file
Get help on a command
Get help on a general topic
Search the whatis database
Make the whatis database
Classify a file




Editing and Printing
DOS Linux Description
edit
n/a
print
n/a
n/a
n/a
edlin
pico
vi
lpr
sed
joe
emacs
ed
Editor for novices
Editor for advanced users
Print a file
Stream editor
Wordstar compatible editor
Programming environment and editor
non-visual editor




Backup, Compression, and Archival
DOS Linux Description
 n/a bzip2 A block sorting file compressor,
using Burrows-Wheeler block sorting
text compression algorithm, and Huffman coding.
bzcat Decompresses files to stdout
bunzip2 A block sorting file compressor
bzip2recover Recover data from damaged bzip2 files.
pkzip zip Create a zip file
pkunzip unzip Extract files from a zip file.
n/a gzip  Compress or decompress files via GNU zip
n/a tar Tape archiver
n/a compress Lempel-Ziv compression program

 

Archivers which you may have used under DOS are available:

name:                
=====    
zip            
unzip                 
lha                    
unarj                  
pkzip251               
arc                    
rar  



Viewing multiple Archives with zip and rar:

 

 

As you probably know, under DOS,  unzip -v filename.zip,  will list the contents of one archive. 
To list the contents of multiple zip or rar archives, enclose the argument in quotes:

unzip -v "*.zip"

example:
 

[bbs@filegate bbbs]$ unzip -v "*.zip"

Archive: nodelist.zip
Length Method Size Ratio Date Time CRC-32 Name


1706292 Defl:N 560625 67% 09-14-99 15:57 a18214bc NODELIST.253
--------          -------  ---                          -------
1706292           560625  67%                            1 file
Archive: ppphowto.zip
Length Method Size Ratio Date Time CRC-32 Name
158718 Defl:N 48642 69% 10-16-99 20:32 b4ad98a9 PPP-HOWTO
--------          -------  ---                           -------
  158718            48642  69%                           1 file
2 archives were successfully processed. 
 
 

tar/gzip:
Tar and gzip are used commonly on Linux.   Often you'll see archives with tgz extensions, .gz, or no extension at all.   
Tar doesn't compress the data, that's why gzip, a compressor,  is used with it.

You can use the file command to see how the file is archived/stored if there is no extension or if you are just curious:
 

[bbs@filegate bbbs]$ file ZPMF025D.TGZ
ZPMF025D.TGZ: gzip compressed data, deflated, last modified: Thu Jun 8 04:55:16 1995, max compression, os: Unix


So you'd need to un-gzip this file first, then un-tar it.

gzip -d ZPMF025D.TGZ

This results in the file ZPMF025.tar

To list the contents of the tar file, type 

tar tf filename.tar 

To extract the tar, type

tar xf filename.tar

There are options to "keep old files" with both gzip and tar which you may also want to include on the command line. The default action is to remove the original tar.   See 

tar --help   and
gzip --h   for more info.

This shortcut extracts both the tar and gzip files in one command:

tar xvzf filename.tar.gz

The "z" flag says "un-gzip before un-tarring".   The same flag works in reverse when tarring. 
 
 
 


Some BASH Scripts

One of the neatest things about *nix systems is that any file can be made executible by simply changing the attributes of the file. 
Of course, if the text file doesn't have any useful commands in it, it won't "do" anything <smile>.

Here are some scripts I've written for my bbs - none of these contain any startling ideas, and I don't doubt a number of them could
be done better, but you can feel free to modify them as you like or need.

info bash will show you the system's man pages for these scripting keywords. 

To use these scripts,  save them to a file and then make them executible with 'chmod a+x filename' without the quotes. 
To call them you can type 'sh filename' without the quotes, where filename is the name of the script. 
Again, scripting is a very broad subject ... looks like I will be writing yet another article concerning that subject later :)

=============mvbad2tic====================
#!/bin/sh
# the above must be the first line in the script. 
# the # symbol specifies a comment line 

mylist="`ls -1 *.bad`"

for file in $mylist
do

        f=`basename $file .bad`.tic
        mv $file $f
done
============end mvbad2tic===============================

=============make_zic====================== 
#!/bin/sh
# make_zic takes a file and it's accompanying
# tic and puts them both in one zip archive aka 
# Allfix's zic option

dir -1 -I*.tic -I*.sh -Iticlist -Iarchives >> archives 
dir -1 *.tic >> /home/bbbs/binkd/work/ticlist 
for file in `cat archives` do
for tics in `cat ticlist`
do
if
test=`grep $file $tics`
then

     f=`basename $tics .tic`
    zip -jm0 $f.zic $file $tics
fi
done
done
mv *.zic /home/bbs/binkd/barry
chown bbs.bbs  /home/bbbs/binkd/barry/*
chmod /home/bbbs/binkd/barry/*
============end make_zic===================
 
 

Next, mvfile2in.sh uses another file you must create named dirlist. 
dirlist contains the names of your users' home directories which will most likely be the same as the username.

You can create this file with the command: dir /home/* -1 > dirlist
Edit it to remove other entries you don't want, like ftp, etc. which may be in the /home directory.

=======mvfile2in.sh====================== 
#!/bin/sh
cd /home/bbbs/
# Move files from a users' inbound to the bbs' inbound 
# Tests to see if user is online before moving anything. 
cd /home/bbbs
for f in `cat /home/bbbs/dirlist`
do
if ps aux | grep ^$f

then
echo "===user $f online==="
elif test -e /home/$f/*/*.bsy
then

echo "$f bsy-flag exists"
else
echo "===safe to move files from $f===" 
mv /home/$f/in/* /home/bbbs/inbound
fi
done
====end mvfile2in.sh==================

get_desc can be used to import file descriptions to a files.bbs or descript.ion type file list.

===========get_desc==================
#!/bin/sh
# import file_id.diz to files.bbs or descript.ion type file 
#
dir -1 *.zip > dirlist
for f in `cat dirlist`
do
unzip -pC $f file_id.diz >> FILE_ID.DIZ
if [ -f FILE_ID.DIZ ] ;
# this script uses an abbreviation for the the test command, [ and ]. 
# I believe Pertti Heikkinen posted this in the bbbs.english echo. 
then

     tr '\n\r' ' ' <FILE_ID.DIZ >tmp.ff
     echo $f `cat tmp.ff` >> descript.txt
     rm -f FILE_ID.DIZ tmp.ff
fi
done
=========end get_desc======================= 
 
 
 
 
 

Some Install Concerns for the SysOp Installing Linux
The first concern is pretty simple. When you log into your system it will be very tempting to login as root, or the superuser,  because user root has no limitations, can run any program,  read/write any file...and ... also can delete every single file on your 

system <grin>.   Issuing a command like rm -r from the / directory as user root will surely go through the entire directory tree 
and do just what you told it to do (rm -r deletes recursively... <ouch>. )

Of course there will be times when you must log on as root to do things such as install your apache web server, configure your ppp connection, etc., but that is really the only time you should log in as root. Likewise, you should never log in as root in XWindows as user root, except as above. XWindows can destroy your data if you are user root and are playing with commands.

_Big_ Tip:

Use the adduser command to create other users on your system which you can use on a daily basis. 
To add a user, as root, type

adduser username

where username is the name you have selected, 8 characters or less. Linux will let you use longer names for the users, but will truncate them.   The adduser command adds the user to the passwd file in /etc/passwd, and unless you specify otherwise, creates a directory off /home which is that user's 'home' directory. These limited-access users can only harm the files they own in their
home directory. Next you assign that user a password with the passwd command by typing

passwd username

The passwd command prompts you for this users' password, 8 characters or less since again it will be truncated if it's over 8 characters. The password you choose should be a combination of upper and lower case alpha characters and numbers.
 

Tip: Try to make the password something that means something to you, then use the letters of the words to make up your password. 
 
For Example:

I Love Chocolate cake I'll take one thanks = ILccIt1t
 
 
 
 


Last Thoughts:


The last section of this article is pretty important. With the number of systems online 24/7, these issues cannot be ignored. If you think your system is safe from those who would test and probe your system for ways of gaining illegal entry, think again.

1.  After installing linux, the very first thing you should do is pull up your favorite text editor, and edit the inetd.conf file which lives in /etc (/etc/inetd.conf).   Comment out every single line in that file except for the one that refers to ftp if you figure to use ftp.   If you think this sounds drastic, well, it is.   And it's necessary.   If you leave the file as is,  you are leaving an incredible number of ports and services open to trouble-makers who will (most likely) be port-scanning your system over and over again looking for weak points. You probably won't need any of the services you are commenting out - and some of them, like rlogin, are incredibly famous for having holes where hackers can gain access to your system.

2.  Use ssh, (Secure Shell) instead of telnet.   Comment telnet out from inetd.conf. If you think are going to need telnet so that you can telnet into your system remotely, DON'T.   Use Secure Shell instead.  If Secure Shell isn't already on your system, go to http://rpmfind.net/   and download and install it.

3.  If your distribution of linux installs wu-ftpd, install a different ftp daemon, such as Bero-ftpd, or Proftpd. Why the switch? 
Well, Wu-ftpd has been known over the years to have holes where creeps can gain illegal access to your system. Technically speaking  these holes are plugged with new releases, but ... in general it is a good idea to install one of the other daemon's mentioned.

4.  All of the above is good, but don't rest easy yet.. Another thing you must do is contantly stay aware of upgrades to the software you use.   If, for example, a new version of bero-ftpd is released,  install it. Upgrades under linux are not always done to make the software prettier or sexy <grin>.  The site that maintains the software you use will always post what type of upgrade the software is and whether it is a security upgrade.

The following articles may be helpful - they contain some of the same information as above, but some additional information as well.


 
 

 
 
 
 
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Copyright 2003 by Janis Kracht
All rights reserved.