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Full Discussion: WTMPX File corrupted
Operating Systems Solaris WTMPX File corrupted Post 302592503 by sebofo on Tuesday 24th of January 2012 04:54:58 AM
Old 01-24-2012
Corrupt wtmpx fixing
In my experience, a corrupt wtmpx (or wtmp) file is ususally due to a write to the file being interrupted in the middle of writing a record. This means that log entries after this event will be shifted a number of bytes which are not a whole record.
The file has fixed-lenghth records. When reading the file from start, and the file is corrupted, there is somewhere a record which is shorter than the record length, and the reading program gets out of synch with the records.
So the way to fix the file is to find and remove the incomplete record. This can be done in a binary-capable editor such as Emacs (I have used that), where you look for recurring patterns to find the start of records, and when you find the short record you remove that and save the file. Formatting it with fwtmp will aid you in finding the number of records you need to pass before reaching the faulty record.
Possibly a simpler method would be to use dd in intelligent ways to first read the uncorrupted part of the file and then skip an offset of a number of bytes until you get output which can be formatted correctly by fwtmp.
What I am getting at is that you don't have to throw away the last part of the file, the information can be recovered by using my method.
Last edited by sebofo; 01-24-2012 at 05:56 AM.. Reason: Added info
 

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LEARN ABOUT SUNOS

fwtmp

fwtmp(1M)						  System Administration Commands						 fwtmp(1M)

NAME

       fwtmp, wtmpfix - manipulate connect accounting records

SYNOPSIS

       /usr/lib/acct/fwtmp [-ic]

       /usr/lib/acct/wtmpfix [file...]

DESCRIPTION

       fwtmp  reads  from  the	standard input and writes to the standard output, converting binary records of the type found in /var/adm/wtmpx to
       formatted ASCII records.  The ASCII version is useful when it is necessary to edit  bad records.

       wtmpfix examines the standard input or named files in utmpx format, corrects the time/date stamps  to  make  the  entries  consistent,  and
       writes  to the standard output.	A hyphen (-) can be used in place of file to indicate the standard input. If time/date corrections are not
       performed, acctcon(1M) will fault when it encounters certain date-change records.

       Each time the date is set, a pair of date change records are written to /var/adm/wtmpx. The first record is the old  date  denoted  by  the
       string  "old time" placed in the line field and the flag OLD_TIME placed in the type field of the utmpx structure. The second record speci-
       fies the new date and is denoted by the string new time placed in the line field and the flag NEW_TIME placed in the  type  field.  wtmpfix
       uses these records to synchronize all time stamps in the file.

       In addition to correcting time/date stamps, wtmpfix will check the validity of the name field to ensure that it consists solely of alphanu-
       meric characters or spaces. If it encounters a name that is considered invalid, it will change the login name to INVALID and write a  diag-
       nostic to the standard error. In this way, wtmpfix reduces the chance that acctcon will fail when processing connect accounting records.

OPTIONS

       -ic	Denotes that input is in ASCII form, and output is to be written in binary form.

FILES

       /var/adm/wtmpx	       history of user access and administration information

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWaccu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       acctcom(1),  ed(1),  acct(1M),  acctcms(1M),  acctcon(1M),  acctmerg(1M),  acctprc(1M),	acctsh(1M),  runacct(1M),  acct(2), acct.h(3HEAD),
       utmpx(4), attributes(5)

       System Administration Guide: Basic Administration

SunOS 5.10							    22 Feb 1999 							 fwtmp(1M)
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