[BusyBox] can't add root user: passwd: unknown uid 0

[michael at michaelshiloh.com]

Thanks Chris and others who responded. I understand now that perhaps my
approach was wrong. The real issue I was having was that even before I 
messed with these files the user "root" was not found. The steps I took
were to try to remedy that.

I will go back to a clean install of busybox and report the original
problem, which should be more meaningful.

The original goal was to get sshd running.

Thanks again,
Michael


On Fri, 29 Jul 2005, Chris Kottaridis wrote:

> I am kind of new to busybox, but a quick perusal of the source I have
> the following comments on the subject.
>
>> The code snippet that's barfing is this, from loginutils/passwd.c:
>>
>>    pw = getpwnam(name);
>>     if (!pw) {
>>         bb_error_msg_and_die("Unknown user %s\n", name);
>>     }
>>     if (!amroot && pw->pw_uid != getuid()) {
>>         syslog(LOG_WARNING, "can't change pwd for `%s'", name);
>>         bb_error_msg_and_die("Permission denied.\n");
>>     }
>
> I think the eror message says:
>
>> #   adduser -h /root root
>> passwd: unknown uid 0
>
> I think that it is my_getug() that is where the failure is:
>
> /* internal function for my_getpwuid and my_getgrgid */
> char * my_getug(char *buffer, char *idname, long id, int bufsize, char
> prefix)
> {
>    if(bufsize > 0 ) {
>        assert(buffer!=NULL);
>        if(idname) {
>            return safe_strncpy(buffer, idname, bufsize);
>        }
>        snprintf(buffer, bufsize, "%ld", id);
>    } else if(bufsize < 0 && !idname) {
>        bb_error_msg_and_die("unknown %cid %ld", prefix, id);
>        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>    }
>    return idname;
> }
>
> It is getting called by my_getpwuid() here:
>
> /* gets a username given a uid */
> char * my_getpwuid(char *name, long uid, int bufsize)
> {
>    struct passwd *myuser = getpwuid(uid);
>
>    return  my_getug(name, (myuser) ? myuser->pw_name : (char *)myuser ,
> uid, bufsize, 'u');
> }
>
> Where getpwuid is failing with uid of zero. So, idname is zero since
> there is no user with uid of zero. and bufsize is being passed with a -1
> from passwd_main() here:
>
>    myname = (char *) bb_xstrdup(my_getpwuid(NULL, getuid(), -1));
>
> This all makes perfect sense, that there is no root entry with uid of
> zero because adduser restricts it's uids to the minimum below:
>
>
> static int passwd_study(const char *filename, struct passwd *p)
> {
>    struct passwd *pw;
>    FILE *passwd;
>
>    const int min = 500;
>    const int max = 65000;
>
>    passwd = bb_wfopen(filename, "r");
>    if (!passwd)
>        return 4;
>
>    /* EDR if uid is out of bounds, set to min */
>    if ((p->pw_uid > max) || (p->pw_uid < min))
>        p->pw_uid = min;
>
>
> So, the moral of the story is that it is wrong to expect adduser to
> create a root user and since you are running as root already my_getpwuid
> is doomed to failure. Because things are setup fully expecting that
> whatever uid you are running as having a valid passwd entry or at least
> one for root.
>
> I'd expect that if you check the passwd file there is a root entry with
> uid of 500, but that's a guess. Personally, I'd be curious if a standard
> Linux commands didn't have a similar problem. A totally empty passwd
> file may not be expected in the code. In partricualr no uid of zero
> entry could screw up a lot of things using getpw* routines.
>
> Anyway, sysadmin of "special" uid values is not handled by adduser, it
> seems that's not what it's for.
>
> I'd do a little more work on this, but I am off on vacation for a week
> and won;t be near a computer.
> -- 
> Chris Kottaridis <chriskot at quietwind.net>
>