System delay and timing mechanism
Unit 3: system sub-delay and timing mechanism
1pat delay
At time
At > Action
At > ctrl+d
St >
At-l
Atrm task number
When the execution action has an output, the output is sent to the initiator of the task in the form of an email
Blacklist and whitelist of at users
/ etc/at.deny # exists by default and takes effect
/ etc/at.allow # does not exist by default. Once it exists (touch / etc/at.allow, in which you can write a user name to be set as a whitelist object, so that both root and whitelist users can use the at command), / etc/at.deny is invalid, and all users except root cannot use the at command.
2, system periodic tasks
Initiated by command:
Crontab-u username-e
Minute 0-59
Hour 0-23
Day of month 1-31
Month 1-12 (or names, see below)
Day of week 0-7 (0 or 7 is Sunday, or use names)
Mm hh dd MM ww
Mm/2, every two minutes.
What time to what time is hh2-hh3?
What time and what time is hh2,hh3
Crontab-l view
Crontab-u username-r cancels periodic tasks
Crontab-e edit file
Initiated by the way of the file
Vim / etc/cron.d/filename
Mm hh dd MM ww username action
Echo'mm hh dd MM username Action'> / etc/cron.d/filename
Black and white list
Vim / etc/cron.deny
Vim / etc/cron.allow
3. Management of temporary files in the system
Vim / usr/lib/tmpfiles.d/*.conf
Type filename perm user group time
A / mnt/westos 1777 root root 10s
Systemd-tmpfiles-create / usr/lib/tmpfiles.d
Systemd-tmpfiles-clean / usr/lib/tmpfiles.d
