Use "sudo" Command without password Prompt

Sometimes you need to run Linux command without password prompt using sudo command.

to learn more about this command read the link here.

For Example i need to run the following command without password prompt, However there are three sudo commands I want to run without entering password:

  • sudo reboot
  • sudo shutdown -r now
  • sudo shutdown -P now
to do this follow the below steps :-
  • edit the following /etc/sudoers file.
  • you find the following lines depend on the username and hostname for the server.

user host = (root) NOPASSWD: /sbin/shutdown
user host = (root) NOPASSWD: /sbin/reboot

This will allow the user user to run the desired commands on host without entering a password. All other sudoed commands will still require a password.

Notes:

  • Always use the command visudo to edit the sudoers file to make sure you do not lock yourself out of the system for example 

sudo visudo -f /etc/sudoers.d/shutdown

  • Using /etc/sudoers.d instead of modifying /etc/sudoers, you could add the two lines to a new file in /etc/sudoers.d for example  /etc/sudoers.d/shutdown.
  • If you did not use visudo to edit your files and then accidentally messed up /etc/sudoers or messed up a file in /etc/sudoers.d then you will be locked out of sudo.to fix it use command pkexec.
Cheers
Osama Mustafa

/usr/ccs/bin/as: not found/No such file or directory on Solaris 11.2

While trying to install Oracle Database 12c on Solaris 11.2 the i faced the following the errors in the logs and dbca was unable to start :-

INFO: sh[2]: /usr/ccs/bin/as: not found [No such file or directory]
INFO: make: Fatal error:
INFO: *** Error code 127

The package developer/assembler comes with default installation, But  Solaris 11 package developer/assembler is not installed.

To install it: –

pkg install developer/assembler

and try again.

Cheers
Osama 

mkdir No such file or directory Solaris 11.2

root@TT:/#mkdir –/u01/app/oracle/product/TimesTen/
mkdir: Failed to make directory “/u01/app/oracle/product/TimesTen/”; No such file or directory

simply this error related to auto_master all you have to do is to remove the entry /home from the auto_master
vi /etc/auto_master

and remove the entry 
Try again.
Thank You 
Osama Mustafa

Enable/Disable SSH For Root User

Sometimes for any reason you want to enable root ssh using any SSH Client such as putty and only the administrator can login to do this follow the below steps :-

  • vi /etc/ssh/sshd_config
  • search for line as follow :-
    • PermitRootLogin yes and change it to –>  PermitRootLogin no
  • Search for the following lines as well :-
    • DenyUsers root user2 user3
  • Remove the root from Deny User
    • DenyUsers user2 user3
  • /etc/init.d/sshd restart

Stopping sshd: [ OK ]

Starting sshd: [ OK ]

If you want to disable the SSH login for root just keep everything like the above.

Cheers
Osama Mustafa

Creating a Local Yum Repository Using ISO Image

In this post i will show you how to create Yum repository Using ISO Image, will save more time :-

  • Download The ISO Image and Upload it to the server.
  • Create Folder Under Root User Like the below

cp /OEL6.6. iso /ISOs

  • now create mount point for this ISO.

mkdir p /var/ISO/OEL6.6
Run the below command to mount it :-

mount o loop,ro /ISOs/OEL6.6. iso /var/ISO/OEL6.6

  • Now under /etc/yum.respos.d you can rename it or set enable=0
  •  Create the following file /etc/yum.respos.d/OEL66.repo
  • Edit the file and add 

[OL66]
name=Oracle Linux 6.6
baseurl=file:///var/ISO/OEL6.6
gpgkey=file:///etc/pki/rpmgpg/
RPMGPGKEY
gpgcheck=1
enabled=1

  • Run the below command to clean yum

yum clean all
yum respolist

The output should be like the below :-

repo id repo name status
OL66 Oracle Linux 6.6 25,459 

Thank you
Osama Mustafa

Dealing with Crontab

Schedule tasks under Linux is an powerful procedure which is used by almost everyone, and to do this using program called cron. more about it here .

Procedure :

make a new text file, and enter this line in that text file like the below :-

crontab myfirstjob

Formatting crontab file :-

what this file contains

Number
Meaning
Allowed range
1
Minutes
0-59
2
Hours
0-23
3
Days
1-31
4
Months
1-12 OR First 3 letters of the Month name
5
Days of the week
0-7 OR First 3 letters of the Day name
6
Name of the program
Any program

Some useful command can be used with cron :-

Show all the task running under cron.

crontab -l

edit the crontab

crontab -e

Some example from crontab file :-

# Minute   Hour      Day of Month       Month                 Day of Week        Command  
# (0-59)     (0-23)     (1-31)             (1-12 or Jan-Dec)    (0-6 or Sun-Sat)              
    0               12           *                             *                         *            /u01/backup.sh

For more example about crontab press here

Cheers
Osama Mustafa

Error in invoking target ‘rat_on part_on dm_on olap_on sdo_on’

Today while i was browsing on Oracle Fourms i found Threads related to 11gR2 Installation , the OP faced an error like the below :-

The above error related to Space On Temp File system all you have to do make sure that there is enough space on temp ( tmp ) or use the below command :-

export TMP=/u01/Foldername
export TMPDIR=/u01/Foldername

Try again now

Cheers
Osama ..  

Linux : Cannot Access …. Input/output error

/bin/ls: reading directory .: Input/output error
total 0

The above error indicate that i cannot access to the specific file on Linux, Delete not working. with root user as well.
so the error is not a problem to delete files, it’s a problem about the file system itself and/or an hardware problem, but before announce that it’s hardware issue 🙂 try the below solution :-

 Option #1:-

use command dmesg.

(display message or driver message) is a command on most Linux- and Unix-based operating systems that prints the message buffer of the kernel. Read about that command here

Option #2 ( worked for me)

Use Fsck command to detect filesystem error and fix it.

How !!!

  1.  First Umount File system ( that file located ). Using Umount command if it’s not able to un mount the file system use lsof command or fuser to check which user using this filesystem.
  2. run the fsck -y /dev/…………….. 
  3. mount file system again.
Fsck Command here
Cheers
Osama …