svcadm enable sar fails to enable sar-优快云博客

本文详细解析了使用 svc-adm 命令在 OpenSolaris 中启用 sar 性能收集工具时遇到的问题。主要问题是 crontab 文件未正确启用，导致性能数据无法被收集。文中还提供了具体的步骤来复现此问题，并给出了解决方案。

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http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6302763

Category
   utility
Sub-Category
   misc
Description
   "svcadm enable sar" does not enable sar. The crontab for sar remains commented out. The problem is with both the /lib/svc/method/svc-sar script, and file permissions in /var/spool/cron/crontabs. The script. assumes that we begin without a sys crontab (which is not the case), and also that we can rm an existing sys crontab (which fails as it runs as the sys user).
The following is the execsnoop DTrace program running while we disable sar,
# execsnoop
  UID    PID   PPID ARGS
    0    820    680 svcadm disable sar
    3    821      7 /sbin/sh -c exec /lib/svc/method/svc-sar stop
    3    821      7 /sbin/sh /lib/svc/method/svc-sar stop
    3    822    821 /usr/bin/who -r
    3    823    821 rm /var/spool/cron/crontabs/sys
On the last line, we can see the "rm" command runs as UID 3. The permissions on the crontabs directory are,
# ls -ld /var/spool/cron/crontabs
drwxr-xr-x   2 root     sys          512 Apr 11 15:23 /var/spool/cron/crontabs
which is why the sys user fails to rm it's crontab file.
Frequency
   Always
Regression
   Solaris 10
Steps to Reproduce
   # svcadm enable sar
# crontab -l sys
Expected Result
   #
# sys crontab
#
# The sys crontab should be used to do performance collection.
# Please note that if the system/sar service is disabled this file
# will be deleted. Please keep a backup copy if you change the
# defaults.
#
0 * * * 0-6 /usr/lib/sa/sa1
20,40 8-17 * * 1-5 /usr/lib/sa/sa1
5 18 * * 1-5 /usr/lib/sa/sa2 -s 8:00 -e 18:01 -i 1200 -A
Actual Result
   #ident  "@(#)sys        1.5     92/07/14 SMI"   /* SVr4.0 1.2   */
#
# The sys crontab should be used to do performance collection. See cron
# and performance manual pages for details on startup.
#
# 0 * * * 0-6 /usr/lib/sa/sa1
# 20,40 8-17 * * 1-5 /usr/lib/sa/sa1
# 5 18 * * 1-5 /usr/lib/sa/sa2 -s 8:00 -e 18:01 -i 1200 -A
Error Message(s)
   none
Test Case

Workaround
   # svcadm enable sar
# chmod 775 /var/spool/cron/crontabs
# svcadm disable sar
# svcadm enable sar