AIX Version 4.3 Differences Guide

files remain as ASCII files, but the design allows for them to be upgraded to
binary files at a later date if this is found to be necessary.
The /etc/passwd and /etc/security/passwd files have been indexed, and the
/etc/security/lastlog file has been indexed with a corresponding change in the way
that this file is processed.
6.6.1 Indexing of the /etc/passwd File
The actual /etc/passwd file has not been changed. However, two new files have
been created, /etc/passwd.nm.idx and /etc/passwd.id.idx, through the mkpasswd
command. These files are indexes created using the username (string) and the
user ID (number) as keys. A record in the index file contains the key, offset of the
corresponding record in the data file (/etc/passwd), and the status of the record.
A negative offset value implies the corresponding record is deleted.
A hook was also added at the point where the file is read to check for the
existence of the index file. If the corresponding index exists, then the index read
mechanism is called with the key as a parameter.
6.6.2 Indexing of the /etc/security/passwd File
The /etc/security/passwd file is a text file that contains one stanza for each user.
It is searched one line at a time looking for the user name. Similar to the
/etc/passwd file, the user name that is physically located at the top of the file is at
an advantage compared to the user name at the bottom of the file. This file is also
indexed by the mkpasswd command. The index is based on the username string as
the key and provides an offset into the file where the stanza can be located. Once
the stanza is located, it is then searched sequentially for the relevant information.
6.6.3 Indexing and Locking /etc/security/lastlog File
The lastlog file is a text stanza file similar to the /etc/security/passwd file that
contains one stanza per user. It is accessed in a similar manner, sequentially
looking for a username. However, unlike the /etc/passwd and
/etc/security/passwd files, this file is accessed for update, which means that
file-locking and crash-recovery must be taken into account. In the existing design,
locking is done at a file-level, and the whole file is backed up, representing a
major overhead. Note that there are no external commands or system and library
calls to access this file. It is accessed internally by the tsmlogin() module to
display lastlog information.
In AIX Version 4.3, the /etc/security/lastlog file remains a text file but has been
changed in the following ways:
Indexed access
An index called /etc/security/lastlognm.id is built using the username
string. This index provides the offset to a stanza. Once a stanza is
located, the lines in it are processed sequentially as in AIX Version
4.2. The index is created by the mkpasswd command.
Fixed record length
Since a user stanza is updated upon login, if the file needed to be
reorganized after every update (because of the variable length text
fields), this would cause the record (or stanza) offsets for all stanzas
after the changed stanza to be changed by a fixed delta. This would
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