Linux Quick Reference for DBAs

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Boot, Last

 who -b
 system boot  2017-10-20 07:26

Boot Log

 last reboot
 reboot   system boot  4.1.12-61.1.18.e Wed Jul 19 08:55 - 09:08  (00:12)    
 reboot   system boot  4.1.12-61.1.18.e Wed Jul 19 08:53 - 09:08  (00:15)    
 reboot   system boot  4.1.12-61.1.18.e Wed Jul 19 08:43 - 09:08  (00:24)    

 wtmp begins Wed Jul 19 08:43:36 2017


  • Display number of cpu's: nproc


  • List: crontab -l
  • Edit: crontab -e
# Min.  Hour  Day   Month  Weekday
# 0-60  0-23  1-31  1-12   0-6 (0 is Sunday)
# Every n minutes = */n

# Every 5 Minutes
*/5 * * * * $SCRIPTS/

# Output Job to File
0 13 * * 0 $SCRIPTS/ > $OUT/ 2>&1
  • Setting TERM in your crontab can avoid output that will create mail entries. Ex: TERM=xterm
  • Using 2>&1 with an .out file can also avoid mail entries.

Run Job Last Day of Month

This can be done testing if next day is "01":
date +%d -d tomorrow


 00 21 * * * [ "$(date +\%d -d tomorrow)" == "01" ] && /mydir/

Inversely (dont run job on last day)

 00 21 * * * [ "$(date +\%d -d tomorrow)" != "01" ] && /mydir/

Run Script on Boot

 @reboot /u01/app/scripts/ > /u01/app/scripts/out/initNFS.out 2>&1

Note @reboot can only from root user cron in some Linux distributions.

cron Output

By default cron outputs to /var/spool/mail/<username>

  • Delete all mail
    • -N Inhibits the initial display of message headers when reading mail or editing a mail folder.
    • d * delete all mails
mail -N
d *

crontab Job Script Suggestions

  • Check what your cron environment actually sees and adjust accordingly:
    * * * * * env > /tmp/env.out
    env.out will show what your cron environment sees.
  • Export vars, i.e. use: set -a
  • Not putting the full path to your scripts in the parent script.
    Ex: DIR_SCRIPTS="/u01/app/scripts"
  • Sourcing global vars during script preamble.
    Ex: source $DIR_SCRIPTS/
  • Include your scripts dir in your PATH.
  • Change (cd) to your scripts dir from your main parent script.
  • Ensure PATH, ORACLE_SID and ORACLE_HOME in your script.
    Alternatively place in crontab.

Preamble Example

 set -a; DIR_SCRIPTS="/u01/app/scripts"; source $DIR_SCRIPTS/
 scrFullName=$(basename "$0"); scrName=${scrFullName%.*}
 scrHistLog="$DIR_LOGS/$scrName.hist.log"; scrOutLog="$DIR_OUT/$scrName.out"

DHCP, Release and Renew Lease

Interface name in example: enp0s8

dhclient -r enp0s8
dhclient enp0s8
ifconfig enp0s8

In VirtualBox get a new IP by: Network-> Adpater -> Advanced -> Refresh MAC address button.

hostname, Changing

Change a systems hostname (to lnx02 example).

  • Run hostnamectl.
    hostnamectl set-hostname lnx02
  • vi /etc/sysconfig/network

VBox: resolv.conf

Set IP to current system.

  1. chattr -i /etc/resolv.conf
  2. vi /etc/resolv.conf
    Example entry line: nameserver
  3. chattr +i /etc/resolv.conf

VBox: dnsmasq

Set IP (listen-address) to current system.

  1. vi /etc/dnsmasq.conf
  1. service dnsmasq restart
  2. If needed: shutdown -r now


Block device attributes (dev, UUID, Type).

 root> blkid
 /dev/sda1: UUID="52226d66-7105-40f2-96c6-c86f3fbbd189" TYPE="xfs"
 /dev/sda2: UUID="pcmBFs-eAo5-Ww9f-fYPU-WpSP-rXFZ-P6YRnk" TYPE="LVM2_member"
 /dev/sdb1: UUID="8373859b-0c53-44ae-be76-927e02fbc0e6" TYPE="xfs"
 /dev/sdc1: UUID="1789294b-ef03-45a9-ad38-1e312e2c253f" TYPE="xfs"
 /dev/sdd1: UUID="dbd3f08e-7a08-4805-8329-a018c47eaa5f" TYPE="xfs"
 /dev/mapper/ol-root: UUID="bd8c4cf8-71bd-41a7-ab4a-077143dfba54" TYPE="xfs"
 /dev/mapper/ol-swap: UUID="a9433d99-5e6f-426b-81cc-5e99879e9bb4" TYPE="swap"
 /dev/mapper/ol-home: UUID="9084822a-a820-406a-a9df-191cface42db" TYPE="xfs"


fdisk can be used to create LINUX disk partitions.

  • Replace /dev/sdb with your disk name.
  • Ensure your OS can see the disk add partition to using: lsblk
  • If for RAC shared disk, you only need to fdisk from node 1.
    Other nodes will see the new partition after /sbin/partprobe run.


  1. Run: fdisk /dev/sdb
  2. Command (m for help): new
  3. Partition type: primary
  4. Partition Number: 1
  5. First sector: <Enter> taking default (first).
  6. Last sector: <Enter> taking default (last).
  7. Command (m for help): w to write changes to disk.

lsblk now shows the attached partition (sdb1)

sdb               8:16   0    8G  0 disk 
└─sdb1            8:17   0    8G  0 part

Repeat above steps for each disk.

Update Partition Table

partprobe is a program that informs the operating system kernel of partition table changes, by requesting that the operating system re-read the partition table.


Disk Device HW Paths

 lshw -class tape -class disk -class storage -short

Example Output:

H/W path          Device      Class       Description
/0/100/1.1        scsi1       storage     82371AB/EB/MB PIIX4 IDE
/0/100/1.1/0.0.0  /dev/cdrom  disk        CD-ROM
/0/100/d          scsi2       storage     82801HM/HEM (ICH8M/ICH8M-E) SATA Contr
/0/100/d/0        /dev/sda    disk        80GB VBOX HARDDISK
/0/100/d/1        /dev/sdb    disk        10MB VBOX HARDDISK
/0/100/d/0.0.0    /dev/sdc    disk        5242KB VBOX HARDDISK

If need be to install: yum install lshw -y

Take Disk Snapshot

 lsblk -S > /tmp/$HOSTNAME.dskinfo1.txt
 lsblk > /tmp/$HOSTNAME.dskinfo2.txt
 lshw -class tape -class disk -class storage -short > /tmp/$HOSTNAME.dskinfo3.txt

Disable Linux Disk IO Scheduler (if to be shared disk for ASM)

Confirm Scheduler Exists

 cat /sys/block/sdb/queue/scheduler
 cat /sys/block/sdc/queue/scheduler


 echo deadline > /sys/block/sdb/queue/scheduler
 echo deadline > /sys/block/sdc/queue/scheduler


Date\Time, Changing

touch -t yyyymmddhhmm
touch -t 201712151500 myfile.txt

Delete Files Older Than x Days

find /stuff -maxdepth 1 -type f -name '*.tar' -mtime +30 -exec rm {} \;

Delete Files Older Than x Minutes

find /stuff -maxdepth 1 -type f -name '*.tar' -mmin +2880 -exec rm {} \;

If you want files in child directories deleted too remove -maxdepth 1.

  60    = 1 hour
  1440  = 1 day
  2880  = 2 days
  10080 = 1 week
  20160 = 2 weeks

Delete Directory and All Files in It

cd /my_parent_dir
rm -r -f my_sub_dir_to_delete

Delete All Files With Spaces

rm -- *\ *

rm -i -- *\ *
Use above method if you want a prompt to confirm each file deletion.


Show the ten biggest files on my system:
find / -printf 'p\n'| sort -nr | head -10

Show All Directories File In
find /u01 -name "*MyString*" -type f -printf '%h\n' > /tmp/find.out; clear; more /tmp/find.out
This method shows a cleaned up output without all the permission denied messages too.

Count Total Files Meeting find Criteria
find /u02/rman/ -maxdepth 1 -type f -name "*.rman" -mtime +1 -print | wc -l


  • find / -name "myscript*.sh" -printf '%h\n'
  • find / -iname "myscript"
  • find /u01/orasw -iname ""
  • grep "10046_Trace" /u01/app/oracle/diag/rdbms/mydb/mydb1/trace/*.trc
    Finds file containing string.

Folder and File Sizes

Find folder\files taking up the most space.

  • cd /parent_folder_with_subfolders_to_check
  • du -shx */


  • cd /folder_to_check
  • du -sh *


 # Permission              File Attributes (User Group Other)
 7 read, write and execute rwx
 6 read and write          rw-
 5 read and execute        r-x
 4 read only               r--
 3 write and execute       -wx
 2 write only              -w-
 1 execute only            --x
 0 none                    ---
 mkdir /u01/rman
 chown -R oracle:oinstall /u01/rman
 chmod -R 765 /u01/rman

fstab and mount

There must be a mount point on the local system to mount a file system. A mount point is a directory to which the mounted file system is attached. The following scenario creates /u01 from the disk partition /dev/sdb.
Note: Disks for ASM only need to be partitioned, i.e. not formatted and mounted.

Create Disk Partitions

 Display existing: lsblk
 Create partition: fdisk /dev/sdb

Ensure Not mounted

 umount -l /dev/sdb1

If need be: umount -f <mtpt>
Create xfs Filesystem

 mkfs.xfs -f /dev/sdb1

 You can only mount file systems, not partitions. An empty partition (one   
 created with fdisk but not initialized with mkfs) cannot be mounted. If
 file -s can’t find a file system inside a disk partition, you cannot mount
 it – you probably forgot to make one using mkfs.

 To check use this: file -s /dev/sdb1

Create Mount Points

 cd /
 mkdir /u01
 mount /dev/sdb1 /u01


 mount | grep /dev/sdb1
 df -h

Make Mount Point Permanent

 vi /etc/fstab
 /dev/sdb1  /u01 xfs  defaults  0  0

 Test /etc/fstab via command: mount -a

 This command mounts everything in the /etc/fstab except for those
 lines that contain the noauto keyword.  In this way you can test 
 without rebooting.

Reboot Check

 shutdown -r now
 mount | grep /dev/sdb1
 df -h

Creating Partitions Larger than 2tb

The following scenario creates a partition larger than 2tb (2.3tb) via ext4 filesystem.

 -- Show Existing Partitions
 root> lsblk

 If need be unmount
  umount -l /u02

 -- Create Partition
 root> parted /dev/sdb
   (parted) mklabel gpt
            Warning: The existing disk label on /dev/sdb will be destroyed 
                     and all data on this disk will be lost. 
                     Do you want to continue? Yes/No? yes
   (parted) unit TB
   (parted) mkpart primary 0.00TB 2.30TB
   (parted) print
   (parted) quit

 root> lsblk

 -- Format New Partition as ext4
 root> mkfs.ext4 /dev/sdb1

 -- Create Mount Point
 root> cd /
 root> mkdir /u02
 root> mount /dev/sdb1 /u02
 root> df -h

 -- Make Permanent
 root> vi /etc/fstab
 /dev/sdb1  /u02 ext4  defaults  0  0

 root> mount -a
  • Ext4 defaults to a 5% overhead so critical daemons can always write. It also prevents fragmentation when disk over 95% used.
    • If not a boot partition you can reclaim it as so: tune2fs -m 0 /dev/sdb1
    • To allocate 1\2 of 1%: tune2fs -m .5 /dev/sdb1
    • To check number of blocks allocated: tune2fs -l /dev/sdb1 | grep 'Reserved block count'
  • Large Disk mkpart Example: mkpart primary 0.00TB 6.00TB
  • The max size for EXT2 type file systems is 2tb.


 lsblk -S
 sda  0:0:0:0    disk VMware   Virtual disk     1.0
 sdb  0:0:1:0    disk VMware   Virtual disk     1.0
 sdc  0:0:8:0    disk VMware   Virtual disk     1.0
 sdd  1:0:0:0    disk VMware   Virtual disk     1.0
 sde  1:0:1:0    disk VMware   Virtual disk     1.0

Oracle Dirs to Routinely Cleanup

# find /u01/ -name "*adump*"         -type d > /tmp/find.out; clear; more /tmp/find.out
# find /u01/ -name "*alert*"         -type d > /tmp/find.out; clear; more /tmp/find.out;
# find /u01/ -name "*trace*"         -type d > /tmp/find.out; clear; more /tmp/find.out;
# find /u01/ -name "*listener*"      -type d > /tmp/find.out; clear; more /tmp/find.out;
# find /u01/ -name "cvures"          -type d > /tmp/find.out; clear; more /tmp/find.out;
# find /u01/ -name "*listener_scan*" -type d > /tmp/find.out; clear; more /tmp/find.out;
# find /u01/ -name "*client*" -type d > /tmp/find.out; clear; more /tmp/find.out|grep

printf "$(basename ""$0""): Started $(date "+%Y-%m-%d %H:%M:%S")\n"
usrStdRet=35;  # Days to retain files, i.e. standard retention.
usrAudRet=10;  # Days to retain Audit files (adump).
usrRmnRet=14;  # Days to retain RMAN files.

# Scripts
find /u01/app/scripts/logs  -type f -name '*.log' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/scripts/tmp   -type f -name '*.tmp' 
  -mtime +$usrStdRet -exec rm {} \;

# oracle: adump
find /u01/app/oracle/admin/mydb/adump -type f -name '*.aud' 
  -mtime +$usrAudRet -exec rm {} \;

# trace
find /u01/app/oracle/diag/rdbms/mydb/mydb1/trace -type f -name '*.tr?' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/oracle/diag/rdbms/mydb/mydb1/trace -type f -name '*.log.[1-9]'  
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/asm/+asm/+ASM1/trace -type f -name '*.tr?' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/crs/lnx01/crs/trace -type f -name '*.tr?' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/rdbms/_mgmtdb/-MGMTDB/trace -type f -name '*.tr?' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/tnslsnr/lnx01/listener/trace -type f -name '*.tr?' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/tnslsnr/lnx01/listener_scan1/trace -type f -name '*.tr?' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/tnslsnr/lnx01/listener_scan2/trace -type f -name '*.tr?' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/tnslsnr/lnx01/listener_scan3/trace -type f -name '*.tr?' 
  -mtime +$usrStdRet -exec rm {} \;

# oracle: alert
find /u01/app/oracle/agent/agent_inst/diag/ofm/emagent/emagent/alert 
  -type f -name '*.xml' -mtime +$usrStdRet -exec rm {} \;
find /u01/app/oracle/diag/rdbms/mydb/mydb1/alert
  -type f -name '*.xml' -mtime +$usrStdRet -exec rm {} \;

# Std Listener
find /u01/app/grid/diag/tnslsnr/lnx01/listener/alert -type f -name '*.log.[1-9]' 
  -mtime +$usrStdRet -exec rm {} \;

# grid: alert
find /u01/app/grid/diag/rdbms/_mgmtdb/-MGMTDB/alert  -type f -name '*.xml' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/tnslsnr/lnx01/mgmtlsnr/alert -type f -name '*.log.[1-9]' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/crs/lnx01/crs/alert          -type f -name '*.xml' 
  -mtime +$usrStdRet -exec rm {} \;

# grid: cvures
find /u01/app/12.1.0/grid/cv/baseline/cvures           -type f -name '*.zip' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/crsdata/@global/cvu/baseline/cvures -type f -name '*.zip' 
  -mtime +$usrStdRet -exec rm {} \;

# grid: gpnp_* Logs
find /u01/app/oracle/product/ -type f -name '*.log' 
  -mtime +$usrStdRet -exec rm {} \;

# RAC Listener
find /u01/app/grid/diag/tnslsnr/lnx01/listener_scan1/alert -type f -name '*.log.[1-9]' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/tnslsnr/lnx01/listener_scan2/alert -type f -name '*.log.[1-9]' 
  -mtime +$usrStdRet -exec rm {} \;
find /u01/app/grid/diag/tnslsnr/lnx01/listener_scan3/alert -type f -name '*.log.[1-9]' 
  -mtime +$usrStdRet -exec rm {} \;

#find /u02/backup/mydb -type f -name '*.rman' -mtime +$usrRmnRet -exec rm {} \;

# End
printf "$(basename ""$0""): Ended $(date "+%Y-%m-%d %H:%M:%S")\n"

gnome, Change default app settings

You must install dconf-editor to change settings via GUI.

  • yum install dconf-editor -y
  • Run: dconf-editor (Run for each user account as desired.)


org -> gnome -> nautilus ->
    default-visible-columns: ['name', 'size', 'type', 'date_modified', 'permissions']
    user-tree-view [x]
    always-use-location-entry  (enables access to pwd top text)
    show-hidden-files [x]


org -> gnome -> gedit-> preferences
    insert-spaces [x]
    tabs-size: 3
    status-bar-visible: [x]
    side-panel-visible: [x] 
    toolbar-visible: [x] 

Interface, Bounce

Format: if[up|down] <InterfaceName>

ifdown ens192
ifup ens192

Interface, Reset Counters Without Bouncing Interface

 -- Determine Interface to Reset (Ex: enp0s9) 

 -- Show Counters
 ifconfig -a enp0s9

 -- Get Driver
 [root]# ethtool -i enp0s9
 driver: e1000

 -- Reset Counters
 modprobe -r e1000; modprobe e1000; ifup enp0s9

 -- Show Counters
 ifconfig -a enp0s9

Set (eth0 example)

vi /etc/network/interfaces

 auto eth0
 iface etho0 inet static

GUI method here.

Interface, Status

 All: ifconfig or netstat -in
 One: ifconfig -a <InterfaceName>
      Ex: ifconfig -a eth0

Set Default Kernel to Use at Boot Menu

The IDs are assigned in order the menu entries appear in the /etc/grub2.cfg file starting with 0. To specify which kernel should be loaded first, pass its number to the grub2-set-default command.

  Print List of Boot Options
  awk -F\' /^menuentry/{print\$2} /etc/grub2.cfg

  Set kernel to Boot
  Example to set it to 2nd line item.
  grub2-set-default 1

  Verify the new default kernel
  Check the below file to see the kernel which will be loaded at next boot, 
  crosscheck the numeric value with the menuentry in the /etc/default/grub file.

  cat /boot/grub2/grubenv |grep saved

  Rebuild GRUB2
  Changes to /etc/default/grub require rebuilding the grub.cfg file as follows:
  grub2-mkconfig -o /boot/grub2/grub.cfg

  Once you have verified everything and rebuilt the GRUB2 configuration file, 
  you can go ahead an reboot the server for changes to take effect.
  shutdown -r now

  To check the current kernel:
  uname -a

Kill a Program

Assuming your process\program name is:

  • View program: ps -ef|grep stdmaint
  • Kill by name: pkill
  • Kill by Process ID:
    • Get Process ID: pgrep stdmaint OR ps -ae|grep stdmaint
    • Kill program: kill <ProcessID>

To check active SQL before and after you can use this:

column executions      format 999999
column username        format a10
column sid             format 999999
column serial#         format 999999
column users_executing format 9999
column sql_text        format a50
SELECT a.executions, 
       b.sid, b.serial#,
FROM v$sql a, v$session b
WHERE users_executing > 0 
AND a.address = b.sql_address 
AND a.hash_value = b.sql_hash_value 
ORDER BY address, child_number;

GUI Apps

  • ASM Cfg Assistent: asmca
  • GEdit: gedit
  • Disk Manager: gnome-disks
  • File Mgr: xdg-open .
  • Firefox: firefox
  • Network Connections:
    • nm-connection-editor
    • redhat-config-network
    • network-admin
  • System Monitor: gnome-system-monitor

The command-line equivalents for any standard menu app can be found by grep-ing/browsing /usr/share/applications. All menu items point to .desktop files. Most are within this directory.


The $HISTFILE variable points to the file that contains your history. So for the oracle user the history file would be:



MTU, Setting

Example setting eth1 to 9000.

 ifconfig eth1 mtu 9000 up
 ifconfig eth1

MTU, Make Value Permanent

If there is no value in interface config file the default (1500) will be used.

  1. cd /etc/sysconfig/network-scripts
  2. vi ifcfg-<Interface>

To make active now (if nothing running on system): service network restart

MTU, Confirming Value

These tests can be used to confirm if a given interface MTU value (ex: 9000) is working on a given interface\IP.


traceroute rac01-priv --mtu 
traceroute -F rac01-priv 9000


ping <privIP> -c 1 -M do -s 8972
PING ( 8972(9000) bytes of data.
8980 bytes from icmp_seq=1 ttl=64 time=0.018 ms

--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
rtt min/avg/max/mdev = 0.018/0.020/0.022/0.004 ms
PING ( 8972(9000) bytes of data.
8980 bytes from icmp_seq=1 ttl=64 time=0.167 ms

If the MTU sizes don’t match the ping command will return “Packet needs to be fragmented by DF set”. The reason for the 8972 on *nix devices is that the ICMP/ping implementation doesn’t encapsulate the 28 byte ICMP (8) + IP (20) (ping + standard internet protocol packet) header – thus we must take the 9000 and subtract 28 = 8972.

Example of forcing an error:

rac02>  ping -c1 -M do -s 9999
PING ( 9999(10027) bytes of data.
ping: local error: Message too long, mtu=9000


iperf server, 
  rac01> iperf -s -u -i 10

iperf client
  rac02> iperf -c rac01-priv -u

-c is saying this is the client side. rac01-priv is my private network IP address 
-u says to send UDP traffic.

Mounting a Windows\Samba Share

On Windows System

  1. Identify windows system to host share (ex: winsrv01).
  2. Create Windows share (ex: oradata).
  3. Create user used to connect mount point to share (ex: orasvc).
  4. Assign privs to user to use data in share.

On Linux System

  1. Ensure cifs-utils installed.
    yum install cifs-utils -y
  2. Create mount point (ex: /mnt/winsrv01).
  3. Issue mount command.
root> mkdir /mnt/winsrv01
root> mount -t cifs //winsrv01/oradata -o username=orasvc,password=MyPassowrd /mnt/winsrv01

root> df -h
      winsrv01/oradata  190T   79T  112T  42% /mnt/winsrv01

Unmount Volume

umount /mnt/winsrv01

df -h shows it gone if successful.

Configure NTP (ntpd)

It is critical that the time of all your nodes is kept in sync for an Oracle RAC environment. Swift changes in time can lead to Oracle shutting down a node(s) due to inconsistent timers.

Disable chrony

  1. systemctl stop chronyd
  2. systemctl disable chronyd.service
  3. systemctl disable chronyd
  4. mv /etc/chrony.conf /etc/chrony.conf.orig
  5. systemctl status chronyd

Install ntpd Package

  1. yum install -y ntp
  2. systemctl enable ntpd
  3. systemctl start ntpd
  4. systemctl status ntpd

Configure Parameter Files

OPTIONS entry:
OPTIONS="-g -x -u ntp:ntp -p /var/run/"

  • -g = panicgate: allows the first adjustment to exceed the panic limit (1000s by default).
  • -p = pidfile: name and path of the file used to record ntpd process ID.
  • -u = Linux user account to own process.
  • -x = slew: make micro time adjustments (rather than in one large adjustment).

Server entry with prefer clause:
server <NTP_Auth_Server_IP> prefer

Restart NTP

  1. systemctl restart ntpd
  2. ntpq -p
In a few minutes you should see a * next to your ntp server.
  remote    refid           st t when poll  reach   delay   offset  jitter
  *myntpsrv     2 u 778  1024    377   5.018   -0.054  0.183


-- Status Checks

  • ntpq -p
  • ntpdc -c loopinfo
  • ntpstat
  • timedatectl <== Alert: Can produce inaccurate results!
  • For RAC as grid user: cluvfy comp clocksync -n all -verbose

-- System Date & Time: View
Tue Nov 22 08:46:20 EST 2016

-- System Date & Time: Set
date MMDDhhmmYYYY
date 112208362016
Tue Nov 22 08:36:00 EST 2016

NTP Misc

-- Stop|Disable

  • systemctl stop ntpd
  • systemctl disable ntpdate

-- Sync NTP Manually
This forces the system time to change to NTP server's time now!

  1. service ntpd stop
  2. ntpdate -s <YourNTPServerIP>
  3. service ntpd start
  4. Check status: ntpq -p

If ntpdate does not work you can use ntpd -qg on that step.

NTP Troubleshooting

Open Office (Apache AKA AOO)

 -- Init Install Dir
 su -
 mkdir -p /u01/sw/aoo
 chmod -R 775 /u01/sw/aoo  

 -- Download
 1. Go to download page.
 2. Select: Linux 64-bit (x86-64) (RPM)  -  English  -  4.1.5 (or latest version)
 3. Select: [Download Full Installation]
    Ex File Downloaded: Apache_OpenOffice_4.1.5_Linux_x86-64_install-rpm_en-US.tar.gz

 -- Copy to Linux System and Extract
 1. cp /media/sf_sw/aoo/Apache_OpenOffice_4.1.5_Linux_x86-64_install-rpm_en-US.tar.gz /u01/sw/aoo/ 
 2. cd /u01/sw/aoo
 3. tar -xvzf Apache_OpenOffice_4.1.5_Linux_x86-64_install-rpm_en-US.tar.gz
    The name of the installation directory will be the language abbreviation: en-US.

 -- Perform rpm Install
 1. cd /u01/sw/aoo/en-US/RPMS
 2. rpm -Uvih *rpm
    By default, this will install Apache Open Office in your /opt directory.
 3. cd /u01/sw/aoo/en-US/RPMS/desktop-integration
 4. rpm -Uvih openoffice4.1.5-redhat-menus-4.1.5-9789.noarch.rpm

 -- Create Desktop Shortcut
 1. Login as your Linux user account.
 2. Left Drag-n-Drop Applications -> Office: Open Office 4.x to desktop.

Package Install\Uninstall\Status

FTP package (vsftpd) used in these examples.

Install Package

 yum install vsftpd -y
 chkconfig --levels 235 vsftpd on
 service vsftpd start

Uninstall Package

 -- Stop & Disable Service
 service vsftpd stop
 chkconfig --levels 235 vsftpd off  

 -- Remove Pkg
 1. Get exact pkg name
    rpm -qa | grep vsftp
 2. Uninstall Pkg
    rpm -e vsftpd-3.0.2-22.el7.x86_64

Check Status

 service vsftpd status
 pgrep ftp
 rpm -qa | grep vsftp

chkconfig --list shows startup status of all packages and run levels.


Core Recommended Settings

 - Session
   Port: 22
   Conn Type: (x) SSH
 - Connection
   Seconds between keepalives: 30
   + SSH -> X11
            [x] Enable X11 Forwarding
            X display location: localhost0
            (x) Remote-Magic-Cookie-1

Create New Session Using Color-Theme

  • Get color-themes.
  • View color-themes.
 0. Close all Putty sessions.
 1. Change Putty Default Session by Double-clicking on desired color-theme .reg file.
 2. Launch Putty
    a. Select "Default Settings".
    b. Press [Load]
 3. Set Values for New Session
    a. Hostname (or IP): MyHostnameOrIpHere
    b. Saved Sessions:   MyNewSessonNameHere
 4. Press [Save]

Run Putty From Cmd Line

putty.exe -ssh [user]@[host] [port] -pw [Password]

 putty.exe -ssh root@ 22 -pw MyPassword


scp sets up a tunnel using ssh and then transfers the file over that tunnel, with an ssh command on the far end to catch the file as it comes over. If the hostname does not work try the IP and vice-versa.

Pull (get file from remote server)

  scp RemoteUser@RemoteHost:FullPath2RemoteFile /LocalDestDir 
  scp oracle@ /u02/exports

Push (copy file to remote server)

  scp /SrcPath/SrcFilename RemoteUser@RemoteHost:/DestPath/DestFilename
  scp /u02/exports/MyDB.dmp oracle@

Notice with push the file to copy needs to be specified on both sides.

Automate Password Prompt via sshpass

yum install wget
rpm -ivh sshpass-1.05-1.el6.x86_64.rpm
which sshpass

sshpass -p 'mypassword' scp /temp/myfile.dmp oracle@

sshpass rpm is here.

scp to Samba Mount Point Method

 sshpass -p 'MyrootPw' scp /u03/exports/oradb1.20180716.tar root@localhost:/mnt/smb01/exports

This method allows you to copy a file to a mount point that only allows root using a non-root account (oracle etc.).


The following covers Linux system changes required to be able to send an email using sendmail.


  • yum install m4 telnet mailx -y
  • yum install sendmail sendmail-cf -y

Relay Server Configuration (if used)

  • cp /etc/mail/ /etc/mail/
  • vi /etc/mail/
    Note: Remove dnl entry at the beginning of line to uncomment the line.
    • Uncomment and change SMART_HOST entry to your relay email server.
    define(`SMART_HOST', `relay.myrelayserver.local')dnl
    • Uncomment and change MASQUERADE_AS entry to your email server.
    • Uncomment FEATURE(masquerade_envelope).
  • Rebuild
    • cd /etc/mail
    • make
    • service sendmail restart


tail -f /var/log/maillog


mail -s "Subject" ReceverEmailAddress@Domain < PathToEmailMsgFile

mail -s "Email Test 1" < /dev/null
mail -s "Email Test 2" < /tmp/MyEmailMsg.txt
mail -s "Email Test 3" "" < /dev/null

Attachment Example
mail -a /u01/app/scripts/rpt/db_growth.csv -s "Growth Rpt" < /dev/null



 systemctl list-unit-files
 systemctl list-unit-files|grep enabled
 systemctl list-unit-files|grep httpd


View Full List of Services Using chkconfig
chkconfig --list

View Full List of Services That Start at Boot (Normally, Runlevel 3)
chkconfig --list | grep 3:on

Turn On a Service for the Default Run Levels (2,3,4,5)
chkconfig httpd on

Turn Off a Service for the Default Run Levels (2,3,4,5)
chkconfig httpd off

Turn On a Service for a Selected Run Level
chkconfig --level 3 httpd on

It is also possible to combine multiple levels into one command:
chkconfig --level 35 httpd on

Turn Off a Service for a Selected Run Level
chkconfig --level 3 httpd off


 Reboot:                        shutdown -r now
 Shutdown and Power Off (halt): shutdown -h now

System Messages

# less /var/log/messages
# more -f /var/log/messages
# cat /var/log/messages
# tail -f /var/log/messages
# grep -i error /var/log/messages

Common Linux log files names and usage

  • /var/log/messages : General message and system related stuff
  • /var/log/auth.log : Authenication logs
  • /var/log/kern.log : Kernel logs
  • /var/log/cron.log : Crond logs (cron job)
  • /var/log/maillog : Mail server logs
  • /var/log/httpd/ : Apache access and error logs directory
  • /var/log/boot.log : System boot log
  • /var/log/secure or /var/log/auth.log : Authentication log
  • /var/log/utmp or /var/log/wtmp : Login records file
  • /var/log/yum.log : Yum command log file.

Redhat SOS Report Generation

 -- Install
 # yum install sos

 -- Standard Report Run (outputs file to /tmp)
 # sosreport

 -- List Plugins
 # sosreport -l > /tmp/sos_info.txt

 -- Example Custom Runs
 Ex 1: Disable filesys, nfs and nfsganesha plugins.
 # sosreport -n filesys,nfs,nfsganesha

 Ex 2: Disable memory and samba plugins, turn off rpm -Va collection:
 # sosreport -n memory,samba -k rpm.rpmva=off

 -- Help Screen
 # sosreport --help

Create\Add New SWAP (using a file)

Change count=8096 to match size you need for SWAP.

-- Create

 dd if=/dev/zero of=/swapfile-additional bs=1M count=8096
 mkswap /swapfile-additional
 chmod 600 /swapfile-additional

-- Make Permanent

 vi /etc/fstab
 /swapfile-additional swap swap    0   0

-- Mount and Enable

 mount -a
 swapon -a

-- Check

 swapon -s
 free -m

Changing SWAP

If required you can enable or repoint the SWAP to another disk after the OS install using these steps:

  1. Allocate a new disk from VirtualBox or your OS (Ex: sdb).
  2. Disable existing SWAP (Ex: /dev/mapper/ol-swap)
    swapoff /dev/mapper/ol-swap
  3. Enable the new disk as your SWAP.
    mkswap /dev/sdb
    swapon -f
  4. Make permenent by editing your /etc/fstab file.
    Line entry: /dev/sdb swap swap defaults 0 0
  5. Reboot to test.
    shutdown -r now


Create (tar all files in current dir)

 tar -cvof scripts.tar * [options]
  • Delete tar'd files option: --remove-files scott*.dmp
  • Exclude files otpion: --exclude '*.tar'


 tar -xvf scripts.tar

List Contents:

 tar --list --file=scripts.tar


Port Check

telnet [host] [port]

 telnet 5500

 -- OK
 Connected to
 Escape character is '^]'.

 -- Could Not Connect
 telnet: connect to address Connection refused

nmap can be used to ping ports as so: nmap -p 5500

Email Creation

mail from: oracle@MyHostName
rcpt to:

Subject: Test

Hello, this is a test.

tmpfs: /dev/shm

The value of /dev/shm must be larger than your Oracle MEMORY_TARGET value. For instance, if you want your database to use 2048m you could set /dev/shm to 2304m.

Short Term

 mount -t tmpfs shmfs -o size=2304m /dev/shm


 vi /etc/fstab and add this entry:
 shmfs /dev/shm tmpfs size=2304m 0

Display Current Value

 df -h

7.x Bug Workaround (per Doc ID 2065603.1)
Upon a fresh install of OL7, the /dev/shm is not mounted in /etc/fstab. It is done in: /usr/lib/dracut/modules.d/99base/

 # ll /usr/lib/dracut/modules.d/99base/
 -rwxr-xr-x. 1 root root 11379 Mar 26 10:14

 vi /usr/lib/dracut/modules.d/99base/ and comment the below lines

 if ! ismounted /dev/shm; then
 mkdir -m 0755 /dev/shm
 mount -t tmpfs -o mode=1777,nosuid,nodev,strictatime tmpfs /dev/shm >/dev/null

Alternatively you can still re-add it to the /etc/fstab

 tmpfs  /dev/shm  tmpfs   defaults,size=2g  0 0


z = color mode
t = cpu    (graphic mode)
m = memory (graphic mode)
c = COMMAND detail
j = Justify COMMAND

u = show for just one user
W = Write changes to file (set default values).
Y = Inspect PID

Update OS

root> yum update -y


0. Login as root user.
1. Applications -> System Tools -> Software Update
2. Continue.
3. Process runs that checks for updates.
4. Next a Window showing how many updates are available displayed.
5. Select [Install Updates].

User Accounts


 -- Example 1
 useradd lnxuser
 passwd lnxuser

 -- Example 2
 useradd --uid 54321 --gid oinstall --groups dba,oper,asmdba,asmoper,backupdba,dgdba,kmdba oracle
  • Required entries are created in the /etc/passwd, /etc/shadow and /etc/group files.
  • Set file permissions as required.
  • Add group: groupadd --gid 54321 oinstall


 userdel -r scott

The -r removes files in the user's home directory along with the home directory itself and the user's mail spool.


  1. Login as root.
  2. Applications Menu -> System Tools -> Settings
  3. Users
  4. Select user, then set Automatic Login to ON.

From this point on when system starts the selected user will automatically login.

Version and Relase Info

  • Kernel version: uname -r
    Example: 4.1.12-94.3.9.el7uek.x86_64
  • Release: cat /etc/redhat-release
    Example: Red Hat Enterprise Linux Server release 7.4 (Maipo)


vi cheat sheet here.

  • Delete
    • To EOL: D
    • Current line to top: dgg
    • Current line to bottom: dG
  • Find string: <Esc> :/EnterString
  • Line Numbers: <Esc> :set number |set nonumber
  • Move
    • Screen (top|middle): H|M
    • File (top|end): gg | shift+g
    • Line (beginning|end):0 | $
    • Page (forward|Back): Ctrl+f|Ctrl+b
  • Search and Replace: <Esc> :%s/pattern/replace/
  • Turn hilite off: <Esc> :noh
  • Write & Quit: <Esc> :wq!
  • Quit: <Esc> :q


With Xming you can launch GUI Linux applications from a putty session.

Xming Initial Client Cfg

  • Run: Xming XLaunch
  • Select display settings: (x) Multiple windows
  • Select how to start Xming: (x) Start a program
  • Enter or choose one X client to Run Local or Run Remote:
    • Start program: xterm default
    • (x) Run Local default
    • Specify parameter settings: [x] Clipboard default

Putty Settings

Set the following putty values to use Xming: Connection -> SSH -> X11

  X11 forwarding
    [x] Enable X11 forwarding
    X display location: localhost:0
  Remote X11 authentication
     (x) MIT-Magic-Cookie-1

Ensure XMing is running before you run your putty session and launch a GUI app.

Disk Info

 su -
 lsblk    > /tmp/$HOSTNAME.lsblk.txt
 lsblk -S > /tmp/$HOSTNAME.HCtrlID.txt
 blkid    > /tmp/$HOSTNAME.blkid.txt
 lshw -class tape -class disk -class storage -short > /tmp/$HOSTNAME.lshw.txt

 su -
 export ORACLE_HOME=/u01/app/ 
 ls -alrt /dev/oracleafd/disks/*              > /tmp/$HOSTNAME.asmfd_disks.txt
 $ORACLE_HOME/bin/asmcmd afd_lslbl '/dev/sd*' > /tmp/$HOSTNAME.asmfd_lbls.txt

 su -
 ls -al /dev/asm* > /tmp/$HOSTNAME.udev_disks.txt

 su - grid
 ls -l /dev/oracleasm/disks    > /tmp/$HOSTNAME.asm_ls.txt
 /usr/sbin/oracleasm listdisks > /tmp/$HOSTNAME.asm_listdisks.txt