What is the number Value permission for the file etc shadow?
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10 More Discussions You Might Find Interesting1. UNIX for Dummies Questions & AnswersShadow file helpAs a part of linux hardening In shadow file all Application accounts which are not locked must contain only an asterisk �*� in the Passwd field. But how would i do it by using command? Is there any way other than modifying shadow file to accomplish this task? (3 Replies) Discussion started by: pinga1232. Shell Programming and Scriptingksh; Change file permissions, update file, change permissions back?Hi, I am creating a ksh script to search for a string of text inside files within a directory tree. Some of these file are going to be read/execute only. I know to use chmod to change the permissions of the file, but I want to preserve the original permissions after writing to the file. How can I... (3 Replies) Discussion started by: right_coaster3. Shell Programming and ScriptingShadow fileHi, In shadow file smithj:Ep6mckrOLChF.:10063:0:99999:7::: 3rd Field 10063 indicates the number of days (since January 1, 1970) since the password was last changed. I want to get the result with script the date on which the password was last changed in YYYY-MM-DD format. can... (8 Replies) Discussion started by: pinnacle4. UNIX for Dummies Questions & AnswersShadow FileI see conflicting definitions for the shadow file. For Solaris, what are the fields please? Thanks. (3 Replies) Discussion started by: DavidS5. UNIX for Advanced & Expert Users/etc/shadow file....Does anyone know what "!!" represents in the password field of the /etc/shadow file? :confused: (6 Replies)
Discussion started by: avcert19986. Solaris*LK* in /etc/shadow filemy etc/shadow file showing *LK* for a particular user.. can u tell me under which circumstances a user is locked (5 Replies) Discussion started by: vikashtulsiyan7. UNIX for Advanced & Expert Usersshadow filewhat does 'x' in the encrypted password field in /etc/shaodw file represent? (3 Replies) Discussion started by: jbashir8. ProgrammingDoubt on shadow fileHi guys, I have a doubt on shadow file ... In the Unix servers in which I am working, I cud see that the shadow file has only one permission set .. tht is read permission for only root user ... (-r--------) .... So my basic doubt here is that how this file is being written then ... only... (4 Replies) Discussion started by: Sabari Nath S9. UNIX for Dummies Questions & Answersshadow fileSirs, What is a shadow file,How it be usefull.For my project i have to keep the password in shawdow file also i am doing in php how can i do it. Thanks in advance, ArunKumar (3 Replies) Discussion started by: arunkumar_mca10. UNIX for Dummies Questions & AnswersShadow file permissionsWe use apaches for a web stuff and we configures apache to use the etc/shadow file for the suers passwords. The problem is when you use passwd to change passwords the password gets put in the shadow file but the permissions before the change was 644 but after the change the permissions got chage to... (1 Reply) Discussion started by: dman110168This tutorial explains the /etc/shadow file in Linux with example. Learn what is the /etc/shadow file and what does it contains. Understanding how the /etc/shadow file is formatted, helps you in managing user accounts in Linux effectively. Historically, the /etc/passwd file used to store all login information in a standalone Linux system. Later, due to following reasons password information was moved in /etc/shadow file.
The /etc/shadow file addresses all above issues.
The /etc/shadow file permissionUnlike /etc/passwd file, the /etc/shadow file is not world readable. It is readable only by the root user or super user. To see this feature in action, access a root shell and run following commands. #su [any regular user account] $cat /etc/shadow $exit #cat /etc/shadow In Ubuntu Linux, by default root account is disabled. If you are following tutorial on Ubuntu Linux, access a super user shell and run following commands. $cat /etc/shadow $sudo cat /etc/shadow [sudo] password for super user Following figure shows above commands with output. As you can see in above figure, when we tried to view the content of /etc/shadow file from a regular user account, shell denied the action. But when we performed the same action from a root user or super user account, shell allowed to it. This security feature keeps encrypted passwords safe from unauthorized users and password cracking programs. The /etc/shadow file formatEach line in /etc/shadow file represents an individual user account and contains following nine fields separated by colons (:).
 Let’s understand each field in detail. UsernameAs we know, except password information, all other login information is stored in /etc/passwd file. This field connects /etc/shadow file with /etc/passwd file. In both files, this field represents login name and stores the exactly same information. When a new user account is created, both files are updated simultaneously. Encrypted passwordThis field stores actual user password in encrypted form. For encryption it uses SHA512 algorithm. In this algorithm, a random salt is mixed with original password before encryption. If two or more users have selected the same password, due to this feature, their encrypted passwords will be different. Controlling LoginLinux does not support blank password in login process. Any user or service which does not have a valid password or have a blank password is not allowed to login. By setting a value other than an encrypted password, this field can be used to control the user login. For example, if the value (!) or (*) is stored in this field, the account will be locked and user or service will not be allowed to login. Both characters (! and *) represent a blank password. The difference between both characters is that, the first character, the exclamation sign (!), is used for user accounts and the second character, the asterisk sign (*), is used for service accounts. If require, a user account can be unlocked by setting a password in this field through passwd command. Following figure shows both values in Ubuntu Linux.
In Ubuntu, by default root account is locked. If you are interested in learning how to enable the root account in Ubuntu, you can check this tutorial. How to enable root user in Ubuntu step by stepIt explains how to enable the root account in Ubuntu step by step. Date of last password changeThis field records the number of days since the user’s password was last changed. To calculate the number of days, it uses 1 January 1970 as a starting day. For example, a user changed his password on 25 June 2018 then the number of days will be 17707. In Linux, the date 1 January 1970 is known as epoch. This date is used as starting date or day in calculation by several commands and configuration files.
To convert a date in days and vice versa, we can use following commands. Without any option and argument this command displays current date. This command calculates the number of days from 1 January 1970 to current date. date -d "1970-01-01 [number of days] days" This command calculates the date from supplied days. It starts counting from 1 January 1970. Following figure shows above commands with output.
Minimum required days between password changesThis field sets the minimum required days that must be elapsed between password changes. Once a password is changed, a user is not allowed to change his password until the days specified in this field are elapsed. If the value is set to 0 (zero), user is allowed to change his password immediately. Maximum allowed days between password changesThis filed sets the maximum allowed days between password changes. Once a password is changed, a user must have to change his password again before the days specified in this field are elapsed. In other word, the days specified in this field are the maximum allowed days for a user to use a password. If this field is set to blank, a user can use his password as long as he wants to use. By default there is a grace period of seven days. A user will be forced to change his password when the days set in this field and extra seven days are passed. Number of days in advance to display password expiration messageThis field sets number of days in advance to display password expiration message. If remaining days to change a password are less than or equal to the days specified in this field, user will get a warning message to change his password. Warning message will be display only when user will be login in command line terminal. This message will not be displayed if user is login in GUI desktop. Number of days after password expiration to disable the accountThis field sets the number of days after password expiration to disable the account. If a user does not change his password in maximum allowed days, his password will be marked as expired. A user account which password is expired will be disabled automatically once the days specified in this field are elapsed. Account expiration dateThis field sets an account expiration date. A user is not allowed to login after the date specified in this field. To specify a date, number of days starting from 1 January 1970 is used. For example, to set account expiration date to 28 June 2018, number 17710 will be used. If this field is set to blank, user account will never expire. Reserve fieldThe last field is reserved for future. Since it’s a reserved field and does not store any value, usually it is skipped while formatting this file. Understanding /etc/shadow file entries with exampleAn entry in /etc/shadow file looks like following. john:$6$iTEFbMTM$CXmxPwErbEef9RUBvf1zv8EgXQdaZg2eOd5uXyvt4sFzi6G4lIqavLilTQgniAHm3Czw/LoaGzoFzaMm.YwOl/:17707:0:90:14::: Following table explains this entry field by field.
That’s all for this tutorial. If you have any feedback or suggestion about this tutorial, please mail me. If you like this tutorial, please don’t forget to share it. By ComputerNetworkingNotes Updated on 2021-06-25 10:04:38 IST Why does etc shadow have the permissions it does?The idea behind setting /etc/shadow permissions to 000 is to protect that file from being accessed by daemons, even when running as root, by ensuring that access is controlled by the DAC_OVERRIDE capability.
What is the ETC shadow file?A shadow password file, also known as /etc/shadow, is a system file in Linux that stores encrypted user passwords and is accessible only to the root user, preventing unauthorized users or malicious actors from breaking into the system.
What is the * mean in shadow file?A password field which starts with a exclamation mark means that the password is locked. The remaining characters on the line represent the password field before the password was locked. So * means no password can be used to access the account, and ! means its locked.
What is ETC shadow and etc passwd?The SunOS release 5.7 passwd command stores encrypted versions of passwords in a separate file, /etc/shadow , and allows only root access to it. This prevents general access to the encrypted passwords that formerly appeared in the /etc/passwd file, which anyone could read.
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