5 Jul
2021
5 Jul
'21
2:53 a.m.
As long ago as the 7th Edition, several binary log files were maintained:
the file generated by acct(2) (one record per process) and the utmp and
wtmp files (one record per login). Both of these are defined by structs in
.h files, so they are definitely not portable (int sizes, endianism, etc.)
5 Jul
5 Jul
1:41 p.m.
John Cowan wrote in
<CAD2gp_SXHQSauT_VibXPvP6PWrFULiMFYkvfs5=YxjHYbHGPwg(a)mail.gmail.com>om>:
|As long ago as the 7th Edition, several binary log files were maintained:
|the file generated by acct(2) (one record per process) and the utmp and
|wtmp files (one record per login). Both of these are defined by structs in
|.h files, so they are definitely not portable (int sizes, endianism, etc.)
And how did you handle it?
On a very current GNU/Linux system these files grow indefinetely,
and sometimes you find several megabytes that track years of data,
and yourself writing (nonetheless quickshot) truncation code like
#?0|kent:~# less bin/truncate-wutmp.sh
#!/bin/sh -
#@ /root/bin/truncate-wutmp.sh
trap 'rm -f /tmp/.doit-${$}.*' EXIT
cat >/tmp/.doit-${$}.c <<'_EOT'
#include <utmp.h>
#include <stdio.h>
int main(){
printf("%lu\n", sizeof(struct utmp));
return 0;
}
_EOT
cc -o /tmp/.doit-${$}.exe /tmp/.doit-${$}.c || exit 1
i=$(/tmp/.doit-${$}.exe)
echo "struct utmp is ${i} bytes"
cd /var/log
s=$(stat -c '%s' wtmp)
[ ${?} -eq 0 ] || exit 2
echo "wtmp size is ${s} bytes"
ix=$((s / i))
echo "... that makes ${ix} utmp entries"
[ ${ix} -gt 42 ] || exit 3
ix=$((ix - 42))
dd if=wtmp of=wtmp.new bs=${i} skip=${ix} || exit 4
mv wmtp.new wtmp
chmod 0644 wtmp
# s-sh-mode
--steffen
|
|Der Kragenbaer, The moon bear,
|der holt sich munter he cheerfully and one by one
|einen nach dem anderen runter wa.ks himself off
|(By Robert Gernhardt)
3:12 p.m.
On Mon, Jul 5, 2021 at 9:42 AM Steffen Nurpmeso <steffen(a)sdaoden.eu> wrote:
And how did you handle it?
The simplest way to truncate the file is with truncate or just ">file",
since writes are small enough to be atomic. The sa utility, which also
goes back to v7, will summarize process accounting data and write it to a
different file; it can then report on either unsummarized data or
summarized data before unsummarized data). Unfortunately Linux has broken
the wtmp/utmp convention of "no logfile, no logging", so a cron job to
truncate wtmp is your only man.
John Cowan http://vrici.lojban.org/~cowan cowan(a)ccil.org
Original line from The Warrior's Apprentice by Lois McMaster Bujold:
"Only on Barrayar would pulling a loaded needler start a stampede toward
one."
English-to-Russian-to-English mangling thereof: "Only on Barrayar you risk
to
lose support instead of finding it when you threat with the charged weapon."
7:25 p.m.
John Cowan wrote in
<CAD2gp_RLYVFx8CK6PAiSrPV8BvSrYHGiB2WPxQGJO=Bh-x3nRA(a)mail.gmail.com>om>:
|On Mon, Jul 5, 2021 at 9:42 AM Steffen Nurpmeso <steffen(a)sdaoden.eu> wrote:
|
|And how did you handle it?
|
|The simplest way to truncate the file is with truncate or just ">file",
|since writes are small enough to be atomic. The sa utility, which also
Hm, ok, sure. I thought maybe, you know. Availability of some
weeks or the quarter of a year is a good thing (tm).
|goes back to v7, will summarize process accounting data and write it to a
|different file; it can then report on either unsummarized data or
|summarized data before unsummarized data). Unfortunately Linux has broken
|the wtmp/utmp convention of "no logfile, no logging", so a cron job to
|truncate wtmp is your only man.
Too bad weather to make something out of that.
The fruits of South Africa were so sweet that we hoped for a good
summer. Well 2000 KM more southern it is, but that Island low
pressure area now lies in front of Ireland i think, what a mess.
Yes the script is not atomic, but good enough for very occasional
usage by a logged in administrator.
--steffen
|
|Der Kragenbaer, The moon bear,
|der holt sich munter he cheerfully and one by one
|einen nach dem anderen runter wa.ks himself off
|(By Robert Gernhardt)
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Steffen Nurpmeso