UNIX Commands for DBAs

This article contains a brief list of commands that most UNIX DBAs will need on a regular basis.

Basic File Navigation

The "pwd" command displays the current directory:

root> pwd
/u01/app/oracle/product/9.2.0.1.0

The "ls" command lists all files and directories in the specified directory. If no location is defined it acts on the current directory:

root> ls
root> ls /u01
root> ls -al

The "-a" flag lists hidden "." files. The "-l" flag lists file details.

The "cd" command is used to change directories:

root> cd /u01/app/oracle

The "touch" command is used to create a new empty file with the default permissions:

root> touch my.log

The "rm" command is used to delete files and directories:

root> rm my.log
root> rm -R /archive

The "-R" flag tells the command to recurse through subdirectories.

The "mv" command is used to move or rename files and directories:

root> mv [from] [to]
root> mv my.log my1.log
root> mv * /archive
root> mv /archive/* .

The "." represents the current directory

The "cp" command is used to copy files and directories:

root> cp [from] [to]
root> cp my.log my1.log
root> cp * /archive
root> cp /archive/* .

The "mkdir" command is used to create new directories:

root> mkdir archive

The "rmdir" command is used to delete directories:

root> rmdir archive

The "find" command can be used to find the location of specific files:

root> find / -name dbmspool.sql
root> find / -print | grep -i dbmspool.sql

The "/" flag represents the staring directory for the search. Wildcards such as "dbms*" can be used for the filename.

The "which" command can be used to find the location of an executable you are using:

oracle> which sqlplus

The "which" command searches your PATH setting for occurences of the specified executable.

File Permissions

The "umask" command can be used to read or set default file permissions for the current user:

root> umask 022

The umask value is subtracted from the default permissions (666) to give the final permission:

666 : Default permission
022 : - umask value
644 : final permission

The "chmod" command is used to alter file permissions after the file has been created:

root> chmod 777 *.log

Owner      Group      World      Permission
=========  =========  =========  ======================
7 (u+rwx)  7 (g+rwx)  7 (o+rwx)  read + write + execute
6 (u+wx)   6 (g+wx)   6 (o+wx)   write + execute
5 (u+Rx)   5 (g+Rx)   5 (o+Rx)   read + execute
4 (u+r)    4 (g+r)    4 (o+r)    read only
2 (u+w)    2 (g+w)    2 (o+w)    write only
1 (u+x)    1 (g+x)    1 (o+x)    execute only

Character eqivalents can be used in the chmod command:

root> chmod o+rwx *.log
root> chmod g+r   *.log
root> chmod -Rx   *.log

The "chown" command is used to reset the ownership of files after creation:

root> chown -R oinstall.dba *

The "-R" flag causes the command ro recurse through any subdirectories.

OS Users Management

The "useradd" command is used to add OS users:

root> useradd -G oinstall -g dba -d /usr/users/my_user -m -s /bin/ksh my_user

• The "-G" flag specifies the primary group.
• The "-g" flag specifies the secondary group.
• The "-d" flag specifies the default directory.
• The "-m" flag creates the default directory.
• The "-s" flag specifies the default shell.

The "usermod" command is used to modify the user settings after a user has been created:

root> usermod -s /bin/csh my_user

The "userdel" command is used to delete existing users:

root> userdel -r my_user

The "-r" flag removes the default directory.

The "passwd" command is used to set, or reset, the users login password:

root> passwd my_user

The "who" command can be used to list all users who have OS connections:

root> who
root> who | head -5
root> who | tail -5
root> who | grep -i ora
root> who | wc -l

• The "head -5" command restricts the output to the first 5 lines of the who command.
• The "tail -5" command restricts the output to the last 5 lines of the who command.
• The "grep -i ora" command restricts the output to lines containing "ora".
• The "wc -l" command returns the number of lines from "who", and hence the number of connected users.

Process Management

The "ps" command lists current process information:

root> ps
root> ps -ef | grep -i ora

Specific processes can be killed by specifying the process id in the kill command:

root> kill -9 12345

uname and hostname

The "uname" and "hostname" commands can be used to get information about the host:

root> uname -a
OSF1 oradb01.lynx.co.uk V5.1 2650 alpha

root> uname -a | awk '{ print $2 }'
oradb01.lynx.co.uk

root> hostname
oradb01.lynx.co.uk

Error Lines in Files

You can return the error lines in a file using:

root> cat alert_LIN1.log | grep -i ORA-

The "grep -i ORA-" command limits the output to lines containing "ORA-". The "-i" flag makes the comparison case insensitive. A count of the error lines can be returned using the "wc" command. This normally give a word count, but the "-l" flag alteres it to give a line count:

root> cat alert_LIN1.log | grep -i ORA- | wc -l

File Exists Check

The Korn shell allows you to check for the presence of a file using the "test -s" command. In the following script a backup log is renamed and moved if it is present:

#!/bin/ksh
if test -s /backup/daily_backup.log
then
  DATE_SUFFIX=`date +"%y""%m""%d""%H""%M"`
  mv /backup/daily_backup.log /backup/archive/daily_backup$DATE_SUFFIX.log
fi

Remove Old Files

The find command can be used to supply a list of files to the rm command:

find /backup/logs/ -name daily_backup* -mtime +21 -exec rm -f {} ;

Remove DOS CR/LFs (^M)

Remove DOS style CR/LF characters (^M) from UNIX files using:

sed -e 's/^M$//' filename > tempfile

The newly created tempfile should have the ^M character removed.

Run Commands As Oracle User From Root

The following scripts shows how a number of commands can be run as the "oracle" user the "root" user:

#!/bin/ksh
su - oracle <

This is often necessary where CRON jobs are run from the root user rather than the oracle user.

Compress Files

In order to save space on the filesystem you may wish to compress files such as archived redo logs. This can be using either the gzip or the compress commands. The gzip command results in a compressed copy of the original file with a ".gz" extension. The gunzip command reverses this process:

gzip myfile
gunzip myfile.gz

The compress command results in a compressed copy of the original file with a ".Z" extension. The uncompress command reverses this process:

compress myfile
uncompress myfile

General Performance

vmstat

$ vmstat 5 3
Displays system statistics (5 seconds apart; 3 times):

procs			memory		page							disk				faults			cpu
r	b	w	swap	free	re	mf	pi	po	fr	de	sr	s0	s1	s2	s3	in	sy	cs	us	sy	id
0	0	0	28872	8792	8	5	172	142	210	0	24	3	11	17	2	289	1081	201	14	6	80
0	0	0	102920	1936	1	95	193	6	302	1264	235	12	1	0	3	240	459	211	0	2	97
0	0	0	102800	1960	0	0	0	0	0	464	0	0	0	0	0	107	146	29	0	0	100

Having any processes in the b or w columns is a sign of a problem system.
Having an id of 0 is a sign that the cpu is overburdoned.
Having high values in pi and po show excessive paging.

• procs (Reports the number of processes in each of the following states)
  • r : in run queue
  • b : blocked for resources (I/O, paging etc.)
  • w : runnable but swapped
• memory (Reports on usage of virtual and real memory)
  • swap : swap space currently available (Kbytes)
  • free : size of free list (Kbytes)
• page (Reports information about page faults and paging activity (units per second)
  • re : page reclaims
  • mf : minor faults
  • pi : Kbytes paged in
  • po : Kbytes paged out
  • fr : Kbytes freed
  • de : anticipated short-term memory shortfall (Kbytes)
  • sr : pages scanned by clock algorith
• disk (Reports the number of disk operations per second for up to 4 disks
• faults (Reports the trap/interupt rates (per second)
  • in : (non clock) device interupts
  • si : system calls
  • cs : CPU context switches
• cpu (Reports the breakdown of percentage usage of CPU time (averaged across all CPUs)
  • us : user time
  • si : system time
  • cs : idle time

CPU Usage

sar

$ sar -u 10 8
Reports CPU Utilization (10 seconds apart; 8 times):

Time	%usr	%sys	%wio	%idle
11:57:31	72	28	0	0
11:57:41	70	30	0	0
11:57:51	70	30	0	0
11:58:01	68	32	0	0
11:58:11	67	33	0	0
11:58:21	65	28	0	7
11:58:31	73	27	0	0
11:58:41	69	31	0	0
Average	69	30	0	1

%usr: Percent of CPU in user mode
%sys: Percent of CPU in system mode
%wio: Percent of CPU running idle with a process waiting for block I/O
%idle: Percent of CPU that is idle

mpstat

$ mpstat 10 2
Reports per-processor statistics on Sun Solaris (10 seconds apart; 8 times):

CPU	minf	mjf	xcal	intr	ithr	csw	icsw	migr	smtx	srw	syscl	usr	sys	wt	idl
0	6	8	0	438	237	246	85	0	0	21	8542	23	9	9	59
0	0	29	0	744	544	494	206	0	0	95	110911	65	29	6	0

ps

$ ps -e -o pcpu -o pid -o user -o args | sort -k 1 | tail -21r
Displays the top 20 CPU users on the system.

%CPU	PID	USER	COMMAND
78.1	4789	oracle	ora_dbwr_DDDS2
8.5	4793	oracle	ora_lgwr_DDDS2
2.4	6206	oracle	oracleDDDS2 (LOCAL=NO)
0.1	4797	oracle	ora_smon_DDDS2
0.1	6207	oracle	oracleDDDS2 (LOCAL=NO)
etc.	etc.	etc.	etc.

The PID column can then be matched with the SPID column on the V$PROCESS view to provide more information on the process:

SELECT a.username, 
       a.osuser, 
       a.program, 
       spid, 
       sid, 
       a.serial#
FROM   v$session a,
       v$process b
WHERE  a.paddr = b.addr
AND    spid = '&pid';

Automatic Startup Scripts on Linux

Create a file in the /etc/init.d/ directory, in this case the file is called myservice, containing the commands you wish to run at startup and/or shutdown.

Use the chmod command to set the privileges to 750:

chmod 750 /etc/init.d/myservice

Link the file into the appropriate run-level script directories:

ln -s /etc/init.d/myservice /etc/rc0.d/K10myservice
ln -s /etc/init.d/myservice /etc/rc3.d/S99myservice

Associate the myservice service with the appropriate run levels:

chkconfig --level 345 dbora on

The script should now be automatically run at startup and shutdown (with "start" or "stop" as a commandline parameter) like other service initialization scripts.

CRON

There are two methods of editing the crontab file. First you can use the "crontab -l > filename" option to list the contents and pipe this to a file. Once you've editied the file you can then apply it using the "crontab filename":

• Login as root
• crontab -l > newcron
• Edit newcron file.
• crontab newcron

Alternatively you can use the "crontab -e" option to edit the crontab file directly.

The entries have the following elements:

field          allowed values
-----          --------------
minute         0-59
hour           0-23
day of month   1-31
month          1-12
day of week    0-7 (both 0 and 7 are Sunday)
user           Valid OS user
command        Valid command or script.

The first 5 fields can be specified using the following rules:

*       - All available values or "first-last".
3-4     - A single range representing each possible from the start to the end of the range inclusive.
1,2,5,6 - A specific list of values.
1-3,5-8 - A specific list of ranges.
0-23/2  - Every other value in the specified range.

The following entry runs a cleanup script a 01:00 each Sunday. Any output or errors from the script are piped to /dev/null to prevent a buildup of mails to root:

0 1 * * 0 /u01/app/oracle/dba/weekly_cleanup > /dev/null 2>&1

Cluster Wide CRON Jobs On Tru64

On clustered systems cron is node-specific. If you need a job to fire once per cluster, rather than once per node you need an alternative approach to the standard cron job. One approach is put forward in the HP best practices document (), but in my opinion a more elegant solution is proposed by Jason Orendorf of HP Tru64 Unix Enterprise Team ().

In his solution Jason creates a file called /bin/cronrun with the following contents:

#!/bin/ksh
set -- $(/usr/sbin/cfsmgr -F raw /)
shift 12
[[ "$1" = "$(/bin/hostname -s)" ]] && exit 0
exit 1

This script returns TRUE (0) only on the node which is the CFS serving cluster_root.

All cluster wide jobs should have a crontab entry on each node of the cluster like:

5 * * * /bin/cronrun && /usr/local/bin/myjob

Although the cron jobs fire on all nodes, the "/bin/cronrun &&" part of the entry prevents the script from running on all nodes except the current CFS serving cluster_root.

NFS Mount (Sun)

The following deamons must be running for the share to be seen by a PC:

• /usr/lib/nfs/nfsd -a
• /usr/lib/nfs/mountd
• /opt/SUNWpcnfs/sbin/rpc.pcnfsd

To see a list of the nfs mounted drives already present type:

exportfs

First the mount point must be shared so it can be seen by remote machines:

share -F nfs -o ro /cdrom

Next the share can be mounted on a remote machine by root using:

mkdir /cdrom#1

mount -o ro myhost:/cdrom /cdrom#1

NFS Mount (Tru64)

On the server machine:

If NFS is not currently setup do the following:

• Application Manager -> System Admin -> Configuration -> NFS
• Select the "Configure system as an NFS server" option.
• Accept all defaults.

Create mount point directory:

mkdir /u04/backup

Append the following entry to the "/etc/exports" file:

/u04/backup

Make sure the correct permissions are granted on the directory:

chmod -R 777 /u04/backup

On the client machine:

If NFS is not currently setup do the following:

• Application Manager -> System Admin -> Configuration -> NFS
• Select the "Configure system as an NFS client" option.
• Accept all defaults.

Create mount point directory:

mkdir /backup

Append an following entry to the "/etc/fstab" file:

nfs-server-name:/u04/backup     /backup         nfs rw,bg,intr 0 0

Finally, mount the fileset:

mount /backup

At this point you can start to use the mount point from your client machine. Thanks to Bryan Mills for his help with Tru64.

PC XStation Configuration

Download the CygWin setup.exe from .

Install, making sure to select all the X11R6 (or XFree86 in older versions) optional packages.

If you need root access add the following entry into the /etc/securettys file on each server:

:0

From the command promot on the PC do the following:

set PATH=PATH;c:cygwinbin;c:cygwinusrX11R6bin
XWin.exe :0 -query 

The X environment should start in a new window.

Many Linux distributions do not start XDMCP by default. To allow XDMCP access from Cygwin edit the "/etc/X11/gdm/gdm.conf" file. Under the "[xdmcp]" section set "Enable=true".

If you are starting any X applications during the session you will need to set the DISPLAY environment variable. Remember, you are acting as an XStation, not the server itself, so this variable must be set as follows:

DISPLAY=:0.0; export DISPLAY

Useful Profile Settings

The following .profile settings rely on the default shell for the user being set to the Korn shell (/bin/ksh).

The backspace key can be configured by adding the following entry:

stty erase "^H"

The command line history can be accessed using the [Esc][k] by adding the following entry:

set -o vi

Auto completion of paths using a double strike of the [Esc] key can be configured by adding the following entry:

set filec

Useful Files

Here are some files that may be of use:

Path	Contents
/etc/passwd	User settings
/etc/group	Group settings for users.
/etc/hosts	Hostname lookup information.
/etc/system	Kernel parameters for Solaris.
/etc/sysconfigtab	Kernel parameters for Tru64.