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Oracle UNIX chmod Letter Designations
Oracle 11g New Features Tips by Burleson
Consulting |
Advanced Oracle Utilities: The Definitive Reference by Rampant
TechPress is written by top Oracle database experts (Bert Scalzo, Donald Burleson, and Steve Callan). The following
is an excerpt from the book.
UNIX chmod Letter Designations
As has been already noted, the chmod command can be used with
letter-based permission masks, as shown in Table 2.4.
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Owner (u)
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Group (g)
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World(o)
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Meaning
|
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rwx
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Rwx
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rwx
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Read + Write + execute
|
|
rw
|
Rw
|
rw
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Read + Write
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rx
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Rx
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rx
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Read + execute
|
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wx
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Wx
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wx
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Write + execute
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R
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R
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r
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Read only
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w
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W
|
w
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Write Only
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x
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X
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x
|
Execute only
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Table 2.4: The UNIX Chmod
Letter Designations
Note how this works. In
the absence of a designator (u, g, or o), the chmod command makes the
change for owner, group and world.
In the chmod command below, make all .ksh files executable for
all users:
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 t.exe
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 u.ora
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 v.sql
root> chmod +x *
root>ls –al
-rwxr-xr-x
1 oracle dba
0 Sep
3 15:40 t.exe
-rwxr-xr-x
1 oracle dba
0 Sep
3 15:40 u.ora
-rwxr-xr-x
1 oracle dba
0 Sep
3 15:40 v.sql
The same operation can be done with the numeric chmod command.
Since the execution permissions are 644, 755 is used to make
all files executable:
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 t.exe
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 u.ora
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 v.sql
root> chmod 755 *
root> ls –al
-rwxr-xr-x
1 oracle dba
0 Sep
3 15:40 t.exe
-rwxr-xr-x
1 oracle dba
0 Sep
3 15:40 u.ora
-rwxr-xr-x
1 oracle dba
0 Sep
3 15:40 v.sql
As noted, the chmod command can be prefaced with a reference to the
user (u), group (g) or others (o).
Consider the following chmod command to allow others (o) to get
write and execute permission:
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 t.exe
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 u.ora
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 v.sql
root> chmod o+wx *
root>ls –al
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 t.exe
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 u.ora
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 v.sql
Note that this is equivalent to changing the permissions from 644 to
647 as shown below:
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 t.exe
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 u.ora
-rw-r--r--
1 oracle dba
0 Sep
3 15:40 v.sql
root> chmod 647 *
root> ls –al
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 t.exe
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 u.ora
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 v.sql
The chmod command can also be used to revoke permissions on file.
As seen in the next example, revoke all permissions for read,
write and execute access for everyone except the owner.
In effect, the permissions are being changed from 647 to 700:
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 t.exe
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 u.ora
-rw-r--rwx
1 oracle dba
0 Sep
3 15:40 v.sql
root> chmod 700 *
root> ls –al
-rwx------
1 oracle dba
0 Sep
3 15:40 t.exe
-rwx------
1 oracle dba
0 Sep
3 15:40 u.ora
-rwx------
1 oracle dba
0 Sep
3 15:40 v.sql
Using chmod to save an Oracle password in a UNIX file: There are
times when there are shell scripts that access Oracle and want to
store the Oracle password in a UNIX file, such that only the UNIX
oracle user can read the file.
In this example, create a file with the Oracle SYSTEM password and
chmod the file so that only the UNIX oracle user can view the
contents:
root>echo manager>system_password.file
root>
chmod 400 *.file
root> ls –al
-r--------
1 oracle dba
8 Sep
3 16:17 system_password.file
This technique is very useful when one wants to write a shell script
to access Oracle and keep the password in a single file.
In addition, the chmod command also has a set of plus operators (+)
that can be used to add read, write, or execute permissions to a file.
Some Korn shell scripts are being changed and it is best to
make them unexecutable for everyone until the change has been
completed:
root> chmod -x *.ksh
root> ls -al *.ksh
-rw-r--r--
1 oracle dba
205 May 10 09:11 a.ksh
-rw-r--r-- 1 oracle
dba
303
May 10 09:11 lert.ksh
-rw-r--r--
1 oracle dba
312
Jul 19 11:32 back.ksh
-rw-r--r--
1 oracle dba
567
May 10 09:12 coun.ksh
Once the maintenance is complete, the scripts can again be made
executable with the chmod +x command:
root> chmod +x *.ksh
root> ls -al *.ksh
-rwxr-xr-x
1 oracle dba
205 May 10 09:11 a.ksh*
-rwxr-xr-x 1 oracle
dba
303 May 10 09:11 lert.ksh*
-rwxr-xr-x
1 oracle dba
312
Jul 19 11:32 back.ksh*
-rwxr-xr-x
1 oracle dba
567
May 10 09:12 coun.ksh*
The savvy DBA will write up a ‘cheat sheet’ with the
basic numeric settings for the chmod commands, and
post it in a handy location.
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A very important area of Oracle UNIX administration, the management of
UNIX directories, will be examined next.
Directory Management in UNIX
Detailed below are the UNIX commands that are used to create,
manage and navigate between UNIX directories.
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