Talk:User identifier
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Shadow does not store numeric IDs
[edit]The UID value references users in the /etc/passwd file. Shadow password files and Network Information Service also refer to numeric UIDs.
This is not accurate enough, because /etc/shadow does not store numeric UIDs, only the username (and password information).
I'm not sure if "Shadow password files" does mean passwd AND shadow, or only shadow. --CrazyTerabyte 19:22, 3 July 2006 (UTC)
tools?
[edit]It would sure be nice here to have a simple example command of how to retrieve UID/usernames in various linux/unix shells.. —Preceding unsigned comment added by 217.56.230.234 (talk) 08:47, 3 September 2007 (UTC)
Nobody
[edit]I dispute that 32767 is "the most-commonly value used for 'nobody'".
The "nobody" user was added when NFS was introduced, as a surrogate for the root user.
Back then, the corresponding numeric UID was 65534 or 4294967294, depending on whether the underlying uid_t type was 16 or 32 bit. These values both correspond to -2 (negative two) after conversion to an "unsigned int" type.
The value -2 was chosen because the usual manner of indicating errors was to return -1, while the usual manner of checking for errors was simply to check for any negative; hence a naive check would say "no such user", while a more sophisticated check would say "nobody".
Sometimes, particularly with System-V derived systems, the numeric value for "nobody" was often forced to meet normal UID allocation policy; hence other outlier values such as 32767 were chosen.
Linux distributions generally followed the earlier BSD policy, but mistakenly continued to use 65534 on kernels with 32-bit UID support.
Martin Kealey (talk) 03:40, 10 September 2013 (UTC)
- The article now goes into more detail about "nobody". Guy Harris (talk) 23:15, 22 March 2026 (UTC)
Expand Special values section with low-uid users?
[edit]Maybe I'm alone in this, but I feel we need historical and current info covering the low-uid users and groups (bin, daemon, adm, lp, sys, et al.) under User_identifier#Special_values. Each one could be an entire research project in itself, so I'm wary of contributing original research. Thoughts? --Rfsmit (talk) 18:37, 23 January 2020 (UTC)
- Perhaps, but that soon dives into the swamp of differences between Unix-like systems (and maybe even between different Linux distributions). Guy Harris (talk) 23:21, 22 March 2026 (UTC)