From 377dda590084f618a7e2e1c19e5acb1487896f34 Mon Sep 17 00:00:00 2001 From: Michael Kerrisk Date: Sun, 29 Jun 2008 07:01:28 +0000 Subject: [PATCH] Rmoved some crufty text; ffixes; --- man5/utmp.5 | 39 ++++++++++++++++++++------------------- 1 file changed, 20 insertions(+), 19 deletions(-) diff --git a/man5/utmp.5 b/man5/utmp.5 index 10f97726e..c5def1364 100644 --- a/man5/utmp.5 +++ b/man5/utmp.5 @@ -55,20 +55,20 @@ around; details depend on the version of libc): .sp /* Values for ut_type field, below */ -#define EMPTY 0 /* Record does not contain valid info - (formerly known as UT_UNKNOWN) */ -#define RUN_LVL 1 /* Change in system run-level (see - \fBinit\fP(8) */ -#define BOOT_TIME 2 /* Time of system booy (in \fIut_tv\fP) */ -#define NEW_TIME 3 /* Time after system clock change - (in \fIut_tv\fP) */ -#define OLD_TIME 4 /* Time before system clock change - (in \fIut_tv\fP) */ -#define INIT_PROCESS 5 /* Process spawned by \fBinit\fP(8) */ -#define LOGIN_PROCESS 6 /* Session leader process for user login */ -#define USER_PROCESS 7 /* Normal process */ -#define DEAD_PROCESS 8 /* Terminated process */ -#define ACCOUNTING 9 /* Not implemented */ +#define EMPTY 0 /* Record does not contain valid info + (formerly known as UT_UNKNOWN on Linux) */ +#define RUN_LVL 1 /* Change in system run-level (see + \fBinit\fP(8) */ +#define BOOT_TIME 2 /* Time of system booy (in \fIut_tv\fP) */ +#define NEW_TIME 3 /* Time after system clock change + (in \fIut_tv\fP) */ +#define OLD_TIME 4 /* Time before system clock change + (in \fIut_tv\fP) */ +#define INIT_PROCESS 5 /* Process spawned by \fBinit\fP(8) */ +#define LOGIN_PROCESS 6 /* Session leader process for user login */ +#define USER_PROCESS 7 /* Normal process */ +#define DEAD_PROCESS 8 /* Terminated process */ +#define ACCOUNTING 9 /* Not implemented */ #define UT_LINESIZE 32 #define UT_NAMESIZE 32 @@ -246,28 +246,29 @@ structure. .SS Comparison with Historical Systems Linux utmp entries conform neither to v7/BSD nor to System V; they are a mix of the two. + v7/BSD has fewer fields; most importantly it lacks \fIut_type\fP, which causes native v7/BSD-like programs to display (for example) dead or login entries. Further, there is no configuration file which allocates slots to sessions. BSD does so because it lacks \fIut_id\fP fields. + In Linux (as in System V), the \fIut_id\fP field of a record will never change once it has been set, which reserves that slot without needing a configuration file. Clearing \fIut_id\fP may result in race conditions leading to corrupted utmp entries and potential security holes. -Clearing the above mentioned fields by filling them +Clearing the abovementioned fields by filling them with null bytes is not required by System V semantics, but makes it possible to run many programs which assume BSD semantics and which do not modify utmp. Linux uses the BSD conventions for line contents, as documented above. .PP -System V only uses the type field to mark them and logs informative messages -such as \fB"new time"\fP in the line field. -\fBUT_UNKNOWN\fP seems -to be a Linux invention. +.\" mtk: What is the referrent of "them" in the following sentence? +.\" System V only uses the type field to mark them and logs +.\" informative messages such as \fB"new time"\fP in the line field. System V has no \fIut_host\fP or \fIut_addr_v6\fP fields. .SH NOTES .PP