Re: Username length limit?

[Lukas Ruf <ruf@rawip.org>]

> Daved Daly <daved.daly@gmail.com> [2004-06-03 12:47]:
>
> On Thu, 03 Jun 2004 12:13:08 +0200, Roel Schroeven
> <rschroev_nospam_ml@fastmail.fm> wrote:
> >
> > Hi,
> >
> > I'm trying to find out the maximum length of usernames on Linux
> > systems (Debian Woody specifically, but I guess it's the same
> > between different distros). Strangely enough, I can't find any
> > clear answer to my question.
> >
> > So I have two questions really: - what is the maximum length of
> > usernames (if any)?
>
> 8chars
>
well, it's been said quite often.  But I doubt!

> > - where can I find authoritative documentation of such things?
>
> uh... uh... google? :P

man getpwent
       The passwd structure is defined in <pwd.h> as follows:

              struct passwd {
                      char    *pw_name;       /* user name */
                      char    *pw_passwd;     /* user password */
                      uid_t   pw_uid;         /* user id */
                      gid_t   pw_gid;         /* group id */
                      char    *pw_gecos;      /* real name */
                      char    *pw_dir;        /* home directory */
                      char    *pw_shell;      /* shell program */
              };

So, there is no clear limit specified.

For the whole line length in passwd (I assume), you can find this
information in <pwd.h>.

  # ifdef __USE_MISC
  /* Reasonable value for the buffer sized used in the reentrant
     functions below.  But better use `sysconf'.  */
  #  define NSS_BUFLEN_PASSWD     1024
  # endif


but in google you can find recommendations not to exceed 16chars.

however, to be really safe and compatible with "older" software
make use of 8 characters only.  For example, older Solaris versions
cause strange errors if you exceed.

wbr,
Lukas
-- 
Lukas Ruf           | Wanna know anything about raw |
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