Skip to main content

Where Linux User Group Information Stored

By
Where does linux stores user and group information?

User names and primary groups are stored in /etc/passwd. This file can be directly edited using the 'vi' editor, although this is not recommended. Format of the file is

* User name (normally all lower case)
* Password (encrypted - only contains the letter 'x')
* User ID (a unique number of each user)
* Primary Group ID
* Comment (Normally the person's full name)
* Home directory (normally /home/
* Default shell (normally /bin/bash)

Each field is separated by a colon.

for example:
# cat /etc/passwd
root:x:0:0:root:/root:/bin/sh
bin:x:1:1:bin:/bin:/bin/sh
daemon:x:2:2:daemon:/usr/sbin:/bin/sh
adm:x:3:4:adm:/adm:/bin/sh
lp:x:4:7:lp:/var/spool/lpd:/bin/sh
sync:x:5:0:sync:/bin:/bin/sync
shutdown:x:6:11:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
uucp:x:10:14:uucp:/var/spool/uucp:/bin/sh
operator:x:11:0:Operator:/var:/bin/sh
nobody:x:99:99:nobody:/home:/bin/sh
admin:x:1001:1000:admin:/home/admin:
guest:x:1002:1000:guest comment:/home/guest:
Says two users admin and guest on my linux box.
Also it is having cat /etc/passwd- file which contains same information as cat /etc/passwd

Passwords for each user are stored in /etc/shadow. This file should only be changed using the passwd command.

example:
# cat /etc/shadow
root:$1$yzGL7ddg$Eb9YHTiaMQ52qDUOkjHLM1:12963:0:99999:7:::
bin:*:12963:0:99999:7:::
daemon:*:12963:0:99999:7:::
adm:*:12963:0:99999:7:::
lp:*:12963:0:99999:7:::
sync:*:12963:0:99999:7:::
shutdown:*:12963:0:99999:7:::
halt:*:12963:0:99999:7:::
uucp:*:12963:0:99999:7:::
operator:*:12963:0:99999:7:::
nobody:*:12963:0:99999:7:::
admin:ddB035VORJOng:0:0:99999:7:::
guest:LkD5clThUzVjw:0:0:99999:7:::
 It is having cat /etc/shadow- file which contains same information as cat /etc/shadow

Group information is stored in /etc/group. This file can be directly edited using the 'vi' editor. Format of the file is

* Group name
* Group password (hardly ever used)
* Group ID
* User names (separated by commas)

Each field is separated by a colon.
example
# cat /etc/group
root:x:0:root
bin:x:1:root,bin,daemon
daemon:x:2:root,bin,daemon
sys:x:3:root,bin,adm
adm:x:4:root,adm,daemon
tty:x:5:
lp:x:7:daemon,lp
uucp:x:14:uucp
ftp:x:50:
nobody:x:99:
users:x:100:
everybody:x:1000:admin,guest
administrators:x:1001:admin
 It is having cat /etc/group- file which contains same information as cat /etc/shadow
There are two groups everybody and administartors with users are admin,guest and admin respectively.
Labels:

Comments

Post a Comment

Popular posts from this blog

Dotnet, .Net 3.5, 2.0, C# Interview Questions

By
Few questions on dotnet, C# 2.0, 3.5 On Object oriented concepts 1)What is inheritance with e.g 2)What is polymorphism -function overloading -Function overriding -virtual keyword use -Static keyword and use -Abstract classes -Interface -Object 3)What is threading and how do we use in realtime application(cognizant) 4)What is threadpooling, lock, monitor(write code sample) 5)Architecture of current project 6)Session state, diffrent types of state management. 7)What is Application_Start, how it works. 8)Type of authentication in asp.net 9)How to configure ASP.NET application. 10) What is Impersonation. 11) What is WebService, WSDL, UDDI, Discovery, asmx files. 12) How to implement WebService and use it. 13) When to use WebServices. 14) WPF, how to implement(BOA) 15) Testing concvepts. 16) Test attributes 17) Flow of Automation Test Method execution 18) Features of dotnet 3.5 19) CLR, garbage collection 20) Finally block 21) Manifest, Metadata, MSIL 22) Assemblies, Type of assemblies, str...
2 comments
Read more

Linux SMB write performance With Simple Tips

By
SMB write performance can be increased by Tuning the buffer cache. The secret to good performance is to keep as much of the data in memory for as long as is possible. Writing to the disk is the slowest part of any filesystem. If you know that the filesystem will be heavily used, then you can tune this process for Linux Samba. writing out dirty blocks to the disk until the filesystem buffer cache is 80 percent full (80). default is 40%, source = http://tldp.org/LDP/solrhe/Securing-Optimizing-Linux-RH-Edition-v1.3/chap29sec287.html by writing echo 80 > /proc/sys/vm/dirty_ratio I am getting around 2MB increase while write operation, tested in Xp. I have tried with this single option, as the ref source is for linux 2.2 and we are using 2.6 kernel. we can try out Linux General Optimization suggested at http://tldp.org/LDP/solrhe/Securing-Optimizing-Linux-RH-Edition-v1.3/gen-optim.html Tried with smb.conf, I am getting around 1MB gain while read and write. socket options = TCP_NODELAY I...
Post a Comment
Read more

The Linux Foundation Free Training Program at linuxfoundation

By
The Linux Foundation Training Program is: * For the Community, by the Community. The Linux Foundation is building the program with its Technical Advisory Board to ensure the content, instructors and classes are the top quality available. * Technically the most advanced. Since the Linux Foundation works directly with community developers, it can cover features and advances in Linux before commercial companies. * Connected. The Linux Foundation has unfettered access to the leading developers and companies in the Linux ecosystem and will use these connections to best position attendees for success. For example, attendees can attend the exclusive, invite-only Collaboration Summit where they can forge connections beneficial to their career. * Real World. The Linux Foundation training courses all have hands on components and a highly rigorous curriculum of programming or administration exercises. Graduates will be well equipped to master Linux programming and system administr...
Post a Comment
Read more