Linux Basic commands for Devops

List of important Commands:

find
tree
chmod
chown
umask



find

Search all empty files in the current directory
find . -type f -empty
where 
. specify current directory
 f specify type file and 
-empty specify empty files

Search only files in the current directory
find . type -f 

Search files in the home directory 
find ~ type -f

Search all empty files in the current directory
find ~ type -d -empty

Find the directories using names
find . -type d -name dir1

Files or directories with 777 permissions
find -type f -perm 0777 
find -type d -perm 0777 

Files with read permissions
find . -type f -perm /u=r

Files with execute permissions
find . -type f -perm /u=x

Find and remove multiple files
find . -type -f -name "*.sh" -exec rm -rf {} \;

Find all hidden files
find . type f -name ".*"

Find last 10 days modify files
find -type f -mtime 10

Find files in the specific directory
find /tmp -type f 
  
Search all empty files in the user home directory 
$ find ~ -type f -empty

Search all empty files on the server
# find / -type f -empty

chmod

How to create a directory using custom permissions?
# chmod -m 755 /dir1

Default values:
ROOT            - 0022
NORMAL     - 0002

Permission table:
User                     Umask        Directory permission     File permission
NORMAL            0002             664                                775

umask

How to calculate the UMASK values for file and directory permissions?

Base Permission for File => 0666
ROOT => 0666 - 0022 = 644
NORMAL => 0666 - 0002 = 664 

Base Permission for Directory => 0777
ROOT => 0777 - 0022 = 755
NORMAL => 0777 - 0002 = 775

How to display the UMASK value?
$ umask

What are the default UMASK value for root and normal user?
User                     Umask        Directory permission     File permission
NORMAL            0002             664                                775
ROOT                   0022            644                                755


How to change the default UMASK value?
# umask 0222 

Note: The value would set to the current specific session but not permanently 

Example: 
# umask
0022   ----------------- default value

# umask 0222

# umask
0222  ----------------- post modified the new UMASK value

How to set UMASK value permanently?
for specific user -> .bash_profile (user home location)
for all users   -----> /etc/profile

Chmod

File or directory Permissions:

r -----------> read ----------->  4 
w-----------> write ---------->  2
x -----------> execute  -------> 1

If  664 means -----> rw-rw-r--

Owner      Group    Others
rw-            rw-            r-- 

read permission ======>     chmod +r  <file_name>
Execute permission ===> chmod +x <file_name>
Execture permission only for User ====> chmod u+x <file_name>
Write permission for user + group + others ===> chmod ugo+w <file_name>

Grants multiple permissions with a single command:

chmod u+rwx, g+x <file_name>


Tree





What is Inode?

It's a data structure, It can store file or directory information like permissions, owner, group name, size, timestamp. However, Inode doesn't contain file-name or directory-name.

display inode number: using "i" option

# ls -li
total 0
  721864 drwxr-xr-x. 2 root root  6 Jan 18 17:58 DevOps
12792107 drwxr-xr-x. 3 root root 18 Jan 18 17:57 dir1
 4326266 drwxr-xr-x. 2 root root  6 Jan 18 17:58 Python
 8657718 drwxr-xr-x. 2 root root  6 Jan 18 17:59 Scripts

 

Comments

Post a Comment

Popular posts from this blog

Auditing in Oracle database

Unified Auditing: Oracle Database 12c Release 1 introduces a new auditing feature called Unified Auditing (12.1). Oracle Unified Auditing modifies the database's fundamental auditing capabilities. In earlier versions of Oracle, each component has its own audit trail. With unified auditing, all auditing is compiled into a single repository and view. Due to the fact that all audit data is now in a single location and a single format, there is a double simplification as a result. This data is made available in a consistent format in the UNIFIED AUDIT TRAIL data dictionary view, which is made possible by the unified audit trail, which is stored in a read-only table in the AUDSYS schema in the SYSAUX tablespace.  DBAs can build audit rules and then assign them to various users using Oracle 12c Unified Auditing, which has the same advantages as giving users varying system capabilities based on their responsibilities. The unified_audit_trail database will contain all of the audit records....
Read more

rs.stepDown() in MongoDB replication

It instructs the primary of the replica set to become a secondary. After the primary steps down,the eligible secondaries will hold an election for primary. Generally, the rs.stepDown() does not immediately step down the primary. If no electable secondaries are up to date with the primary, the primary waits up to secondaryCatchUpPeriodSecs (by default 10 seconds)  for a secondary to catch up. Once an electable secondary is available, the method steps down the priamry.  Once stepped down, the original primary becomes a secondary and is ineligible from becoming primary again for the remainder of time specified by stepDownSecs. The rs.stepDown() method attempts to terminate long-running user's operations that block the primary from stepping down, such as an index build, a write operation, or a map-reduce job. Syntax: rs.stepDown(stepDownSecs, secondaryCatchUpPeriodSecs)
Read more

Tuples in Python

 Tuples Basically Tuples in Python are very similar to Lists, but, Tuples are immutable which means that they can not be modified/changed. We generally use Tuples to make sure the values are not changed like, dates, Year, and days of the week or dates on a Calendar.  Creating a Tuple: >>> my_t1=(1,2,3) >>> my_t2=('one','two','three') >>> my_t1 (1, 2, 3) >>> my_t2 ('one', 'two', 'three') -- check the length of tupple: >>> len(my_t1) 3 >>> len(my_t2) 3 -- Tuples can have mixed objects as like Lists. >>> my_t3=(1,'two',3,'four') >>> my_t3 (1, 'two', 3, 'four') -- indexing with tuples  >>> my_t3=(1,'two',3,'four') >>> my_t3[2] 3 Immutable Tuples We can not modify the value. Here is the example: >>> my_t3=(1,'two',3,'four') >>> my_t3[2]=4 Traceback (most recent call last):  ...
Read more