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In addition to the more widespread useradd, Debian based systems also contain an additional adduser command which provides a higher level interface for adding users and some related tasks. There are various questions/answers on other SE sites which detail the basic differences between these commands, for example:

Most of the answers essentially say that adduser provides nicer interface for adding users interactively, but don't give much detail on what happens when adduser is run that doesn't compared to useradd. So:

  1. What does adduser do that useradd doesn't?
  2. What commands do I need to use to produce equivalent results?
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1 Answer 1

up vote 20 down vote accepted

First off, the respective man page snippets highlight the differences between the two commands and give some indication of what is going on. For adduser:

adduser and addgroup add users and groups to the system according to command line options and configuration information in /etc/adduser.conf. They are friendlier front ends to the low level tools like useradd, groupadd and usermod programs, by default choosing Debian policy conformant UID and GID values, creating a home directory with skeletal configuration, running a custom script, and other features.

Then for useradd:

useradd is a low level utility for adding users. On Debian, administrators should usually use adduser(8) instead.

Further investigation of adduser reveals that it is a perl script providing a high level interface to, and thus offering some of the functionality of, the following commands:

  • useradd
  • groupadd
  • passwd - used to add/change users passwords.
  • gpasswd - used to add/change group passwords.
  • usermod - used to change various user associated parameters.
  • chfn - used to add/change additional information held on a user.
  • chage - used to change password expiry information.
  • edquota - used to change disk usage quotas.

A basic run of the adduser command is as follows:

adduser username

This simple command will do a number of things:

  1. Create the user named username.
  2. Create the user's home directory (default is /home/username and copy the files from /etc/skel into it.
  3. Create a group with the same name as the user and place the user in it.
  4. Prompt for a password for the user.
  5. Prompt for additional information on the user.

The useradd program can most of accomplish most of this, however it does not do so by default and needs additional options. Some of the information requires more commands:

useradd -m -U username
passwd username
chfn username

Note that adduser ensures that created UIDs and GIDs conform with the Debian policy. Creating normal users with useradd seems to be ok, provided UID_MIN/UID_MAX in /etc/login.defs matches the Debian policy. What is a problem though is that Debian specifies a particular range for system user UIDs which only seems to be supported in /etc/adduser.conf, so naively adding a system user with useradd and not specifying a UID/GUID in the correct range leaves the potential for serious problems.

Another common use for adduser is to simplify the process of adding a user to a group. Here, the following command:

adduser username newgroup

replaces a more complex usermod command that requires the groups which the user is already a member of (and that you would like the user to remain a member) to be specified:

usermod -G all,other,groups,user,is,in,newgroup

One downside to using adduser here though is that you can only specify one group at a time.

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This is cool! I didnt even know this was a question. Does it take hashed passwords as useradd does? This is very good work, by the way. –  mikeserv Mar 23 at 23:47
    
I don't know if I completely agree with the "administrators should..." statement though... Personally, I believe the administrator should probably be putting together his/her own adduser according to a system-wide policy, but that's just armchair quarterbacking at best. –  mikeserv Mar 23 at 23:51
    
@mikeserv, no there are no hashed passwords. There is another program you should know about though - chpasswd - this can accept hashed passwords on stdin. I will wait til tomorrow before I update that other answer though I think. –  Graeme Mar 24 at 0:09
    
nice post. For me a little too much details. What I miss most is, that adduser was originally created for server admin's who frequently needed to create/modify/limit real users like on an email server at university. With adduser you can automate the process. This changed a little during the years so nowadays useradd can be to difficult for many admins and for them adduser has become the tool of choice. –  bersch Mar 24 at 0:29
    
Shouldn't useradd username newgroup be adduser ... instead? –  Ruslan Mar 24 at 10:27

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