Oracle UNIX Administration Command History Oracle UNIX/Linux Tips by Burleson Consulting

Using the Command history file in UNIX

A special file in the UNIX user home directory called .sh_history is used by UNIX to record and allow for fast retrieval of prior commands.  For example, if you place the set ?o vi command in your .profile file, the use can use <esc> k to scroll back through your command history, and you can use <esc> / string to quickly display a previous command that contains the string. 

You can also use the UNIX history command or fc command to display the previous UNIX commands, and you see a command number that can be used to retrieve the command:.

root> history
423     chmod 700 *.file
424     ls -al
425     chmod 404 *.file
426     chmod 400 *.file
427     ls -al
428     sqlplus /

Here is a listing of a .sh_history file.  Note that it even includes the command that was used to display itself.

root> tail -10 .sh_history
cat alert_envtest.log|wc
cat alert_envtest.log|wc -l
cat alert_envtest.log|grep ORA-00600
cat alert_envtest.log|grep ORA-00600|wc -l

cd
ls -al .s*
tail -10 .sh_history

The .sh_history file is commonly used as an audit mechanism, since each and every UNIX command entered by the UNIX user is stored in their .sh_history file.  Many shops use it to track the behavior of new Oracle DBAs, since inappropriate or inept UNIX commands are easily spotted.

Here is the script that I use to spy on my Oracle DBAs.  When run as root, it provides a list of every command executed by everyone on the Oracle server:

audit_commands.ksh
#!/bin/ksh

for user in `cat /etc/passwd|cut -d ':' -f1`
do
   echo *************************************
   echo UNIX command security audit for $user
   echo *************************************
   cat ~$user/.sh_history
done

Let?s carefully inspect the behavior of this script:

1. It lists the /etc/passwd file using (cat /etc/passwd)

root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:
daemon:x:2:2:daemon:/sbin:
news:x:9:13:news:/var/spool/news:
uucp:x:10:14:uucp:/var/spool/uucp:
operator:x:11:0:operator:/root:
piranha:x:60:60::/home/httpd/html/piranha:/dev/null
postgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash
carl:x:500:100:Carl Marx:/home/carl:/bin/bash
pamela:x:501:100:Pamela Zeus:/home/pamela:/bin/bash
olaf:x:512:512::/home/olaf:/bin/bash
mario:x:514:514::/home/mario:/bin/bash
mysql:x:100:101:MySQL server:/var/lib/mysql:/bin/bash
bugz:x:515:515::/etc/httpd/sites/bugz.rovia.com:/bin/bash
oracle:x:516:517::/home/oracle:/bin/bash
afshin:x:522:523::/home/adamf:/bin/bash
celora:x:525:526::/dev/null:/bin/false
weber:x:527:528:Web CVS:/home/webcvs:/bin/bash

2. It extracts the first colon-delimited field using (cut ?d?:? ?f1)

root
bin
daemon
news
uucp
operator
piranha
postgres
squid
carl
pamela
olaf
marion
mysql
bugz
oracle
afshin
celora
weber

3. It loops through each UNIX user and

4. Lists the contents of their .sh_history file

Next, let?s take a look at the common UNIX shells and see how they allow us to perform common Oracle maintenance.

UNIX shells

There are several ?shells? that are available to support UNIX commands.  A shell can be thought of as a scripting environment, and each shell has different syntax, so it is important that you know what shell you are using when you enter UNIX commands. In this book we will use the Korn shell, but you can write Oracle scripts using any of the available shells.

* Bourne Shell (sh) - The Borne shell was the original UNIX command processor, which was developed at AT&T by Stephen R. Bourne in the early 1970s. This is the official shell that is distributed with UNIX systems. The Bourne shell is the fastest UNIX command processor.

* Bourne Again Shell (bash) - Many UNIX purists prefer the Bourne Again shell, also known as the bash shell.

* C Shell (csh) - Another command processor, developed by William Joy and others at the University of California in the early 1980s, is known as the C shell. The C shell borrows many concepts from the C language, and offers greater versatility than the Bourne shell.

* Korn Shell (ksh) ? Another popular command processor was developed by David Korn in the early 1980s, and is appropriately called the Korn shell. The Korn shell combines many of the best features of the earlier command processors, and it is gaining in popularity among Oracle DBAs.  All of the shell scripts in the book are Korn shell scripts.

Your default shell is set in the /etc/passwd file.  For example, here we see that the root user has the Bourne shell (/bin/sh), the janet user uses the Bourne Again shell (/bin/bash), the oracle user uses the Korn shell (/bin/ksh), and the john user uses the C-Shell (/bin/csh).

root>cat /etc/passwd
root:x:0:1:Super-User:/:/bin/sh
janet:x:100:1::/export/home/janet:/sbin/bash
oracle:x:108:102::/export/home/oracle:/bin/ksh
john:x:108:102::/export/home/john:/bin/csh

Each shell has specific syntax and features (Table 1-2). For the Oracle server environment, the shell chosen is not as important as uniformity.  In other words, the Oracle DBA should choose a shell environment and then requires that all Oracle UNIX scripts be written in that shell.

Remember, it is quite easy to change your shell environment.  You can change your UNIX environment by entering the name of the shell at the UNIX command prompt, and you can change the shell for a UNIX script by entering a shell directive as the first line of the script.  For example, you can change your shell environment to the Korn shell by entering the  ksh command, and you can make a UNIX script use the Korn shell by entering #!/bin/ksh as the first line of the script.  Table 1-3 shows a complete list of commands for changing shell environments.

Interactive shell	Shell Script Command	Shell Name
ksh	#!/bin/ksh	Korn shell
csh	#!/bin/csh	C-Shell
sh	#!/bin/sh	Bourne Shell
bash	#!/bin/bash	Bourne Again Shell

Table 3: Changing UNIX shell environments

In most Oracle shops, the DBA has a choice of shell environments.  As soon as you request a login account for your Oracle server, the first thing the system administrator usually asks you is which shell you prefer.

Using UNIX command options

All UNIX commands support from one to many command options.  To understand how this works, let?s examine the ls command. To illustrate the complexity of UNIX commands, the man ls command shows that the ls command accepts 22 arguments (Table 1-2):

-a	Lists all entries, including those that begin with  a dot (.), which are normally not listed.
-A	Lists all entries, including those that begin  with  a dot  (.),  with the exception of the working directory (.)  and the parent directory (..).
-b	Forces printing of non-printable characters to be in the octal \ddd notation.
-c	Uses time of last modification  of  the  i-node
-C	Multi-column  output  with  entries  sorted  down  the columns.
-d	If an argument is a directory,  lists  only  its  name
-f	Forces each argument to be interpreted as a  directory
-F	Marks directories with a  trailing  slash  (/)
-g	The same as -l, except that the owner is not printed.
-I	For each file, prints the i-node number in  the  first column of the report.
-l	Lists in long format,  giving  mode,  ACL  indication.
-L	If an argument is a symbolic link, lists the  file  or directory  the  link  references  rather than the link itself.
-m	Streams output format; files  are  listed  across  the page, separated by commas.
-o	The same as -l, except that the group is not printed.
-p	Puts a slash (/) after each filename if the file is a directory.
-q	Forces printing of non-printable  characters  in  file names as the character question mark (?).
-r	Reverses the order of sort to get  reverse  alphabetic or oldest first as appropriate.
-R	Recursively lists subdirectories encountered.
-s	Gives size in blocks, including indirect  blocks,  for each entry.
-t	Sorts by time stamp (latest first) instead of by name. The default is the last modification time. (See -u and -c.)
-u	Uses time of last access instead of last  modification for sorting (with the -t option) or printing (with the -l option).
-x	Multi-column output with entries sorted across  rather than down the page.

Table 4: Arguments to the UNIX ls command

One or many of these arguments may be used every time the ls command is invoked and a single minus sign ?-? is used to tell Oracle that arguments are being passed to the command.  For example, the following is a invocation of the ls command using the F, a, r, and t options:

root> ls -Fart
.solregis/                 l.ksh*                     imp_envtest.lst            

One common use of the ls command in Oracle is used to locate the most recently modified file in a directory. We do this by using the ls command with the a, l, and t options, and then pipe the output to the head command.

root> ls -alt|head
total 928228
-rw-------   1 oracle   dba         3372 Sep  3 14:43 .sh_history
-rw-r--r--   1 oracle   dba        19159 Sep  3 08:27 man_sort.lst
drwxr-xr-x  21 oracle   dba         2048 Sep  3 08:27 .
-rwxr-xr-x   1 oracle   dba           55 Aug 22 11:56 afiedt.buf
-rw-------   1 oracle   qmail        437 Aug 12 20:43 .bash_history
-rwxr-xr-x   1 oracle   qmail        415 Aug  1 20:37 mail.out
drwxr-xr-x  10 root     root         512 Jul 26 08:49 ..
drwxr-xr-x   3 oracle   dba          512 Jul 26 08:49 book
-rw-r--r--   1 oracle   dba         2198 Jul 26 08:43 sqlnet.log

Next, net?s examine some common UNIX commands that are used in an Oracle environment.

 

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