network server in linux 1. Briefly describe the purpose of the /etc/passwd, /etc
ID: 3906243 • Letter: N
Question
network server in linux
1. Briefly describe the purpose of the /etc/passwd, /etc/shadow and /etc/group files and describe the relationship(s) between these three files. Note: you do not need to mention the exact format of the files.
2.Regarding backups, consider the /var/spool/mail and /usr/local directories. How often would you perform a full backup of each directory? How often would you perform an increment- al backup of each directory? Justify your answers.
3.What is the difference between cron and at? Describe a situation when you might use each one.
4. How does a UNIX machine know where to locate the kernel to boot?
Explanation / Answer
1)Answer:
/etc/passwd:
/etc/passwd file stores essential information, which is required during login i.e. user account information. /etc/passwd is a text file, that contains a list of the system’s accounts, giving for each account some useful information like user ID, group ID, home directory, shell, etc. It should have general read permission as many utilities, like ls use it to map user IDs to user names, but write access only for the superuser/root account.
The /etc/passwd contains one entry per line for each user (or user account) of the system. All fields are separated by a colon (:) symbol.
/etc/shadow file:
The /etc/shadow file stores actual password in encrypted format for user’s account with additional properties related to user password i.e. it stores secure user account information. All fields are separated by a colon (:) symbol. It contains one entry per line for each user listed in /etc/passwd file.
/etc/group file:
/etc/group is a text file which defines the groups to which users belong under Linux and UNIX operating system. Under Unix / Linux multiple users can be categorized into groups. Unix file system permissions are organized into three classes, user, group, and others. The use of groups allows additional abilities to be delegated in an organized fashion, such as access to disks, printers, and other peripherals. This method, amongst others, also enables the Superuser to delegate some administrative tasks to normal users.
3)Answer:
Cron:
cron command is used to schedule the task daily at the same
time repeatedly.
CRON is for running task at a regular base (every hour, day, first of the month etc), cron job is used to schedule the job. It is used for maintain the daily routing work.
at:
"at" command is used to schedule the task only once i.e to
run only one time
AT on the other hand, is a one-shot. At a certain time (tomorrow at 14:00) a job is started. Once. At schedule the task at only once
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