sudoers grant

For grant sudoers to user in redhat, centos, oralce linux, edit the file /etc/sudoers and append
username ALL=(ALL) ALL
root ALL=(ALL) ALL

For example:

## Next comes the main part: which users can run what software on
## which machines (the sudoers file can be shared between multiple
## systems).
## Syntax:
##     user    MACHINE=COMMANDS
## The COMMANDS section may have other options added to it.
## Allow root to run any commands anywhere

root    ALL=(ALL)     ALL
oracle    ALL=(ALL)     ALL

less command

The navigation keys in less command are similar to Vim editor.

Forward Search

    / – search for a pattern which will take you to the next occurrence.
    n – for next match in forward
    N – for previous match in backward

Backward Search

    ? – search for a pattern which will take you to the previous occurrence.
    n – for next match in backward direction
    N – for previous match in forward direction

For viewing large log files

    CTRL+F – forward one window
    CTRL+B – backward one window
    CTRL+D – forward half window
    CTRL+U – backward half window
    j – navigate forward by one line
    k – navigate backward by one line
    G – go to the end of file
    g – go to the start of file
    q or ZZ – exit the less pager

Useful other command

    v – using the configured editor edit the current file.
    h – summary of less commands
    &pattern – display only the matching lines, not all.

File paging
You can open multiple files by passing the file names as arguments:

$ less file1 file2

virtualbox: mount shared esterno su linux

You have to specify the path and folder to share with the service name on virtualBox

for the mount you can use this command:

sudo mount -t vboxsf nome_servizio /shared_name

you need on your linux OS one folder (mkdir shared_name)

for example if the service name is “stage” and the folder name on the system is shared you can use this command:

sudo mount -t vboxsf stage /shared

for the unmount you can use:

sudo umount -t vboxsf stage /shared


#archive the file without compression.
tar file_name

(1) create tar cfv tar c=create, f=file (on the disk and not on the tape),v=verbose (show file list).

ex: tar cfv archive.tar *.txt create the file’s archive of all txt files in the same path.

ex: tar -cvf /destination_path/filename.tar /path to put in the tar file

(2) tvf to show the content of the archive: tar tfv archive.tar

(3) xfv archive file extraction: tar xfv archive.tar