Lastlog

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lastlog is a program available in most flavors of UNIX based operating systems. It is similar in functionality to the unix program last. However, last parses a different database (wtmp and btmp).

lastlog formats and prints the contents of the last login log file, /var/log/lastlog, including the login name, port, and last login datetime.

The lastlog sparse file mystery on SysV UNIX[edit]

System administrators may be confused by the apparent misreporting of the size of lastlog by utilities such as ls. Since lastlog is a sparse file, its reported file size isn't always the size it consumes on the UNIX file system. The man page for lastlog explains the confusion:

"The lastlog file is a database which contains info on the last login of each user. You should not rotate it. It is a sparse file, so its size on the disk is usually much smaller than the one shown by "ls -l". You can display its real size with "ls -s". " ( See reference ** below )

In addition, it seems to confuse some backup software. Tivoli Storage Manager, for example, will try to load TeraBytes of tapes to back up this file.[1]

In these examples below, you will see that both du and ls report the file as 1.2 TeraBytes, whereas using a different invocation of the command will show the size consumed on the disk:

[root@bogushost]# ls -l lastlog
-r--------  1 root root 1254130450140 Jun 21 19:25 lastlog

[root@bogushost]# ls -lsh lastlog
56K -r--------  1 root root 1.2T Jun 21 19:25 lastlog

[root@bogushost]# ls -sbh lastlog
56K lastlog

[root@bogushost]# du -sh lastlog
56K     lastlog

[root@bogushost]# du -sb lastlog
1254130450140   lastlog

References[edit]

External links[edit]