September 5, 2015-after-school assignments

1. Summarize the detailed usage method of the task plan (at, crontab) on Linux system;

At command: A job that hosts a future run: supports the use of job queues: default to a queue; ctrl+dat [option] ... TIMETIME: (1) Absolute time hh:mm,mmdd[cc]yy, mm/dd/[cc]yy, dd.mm.[cc]yy or [Cc]yy-mm-ddtomorrow (2) Relative time now+ #UNITminute, hour, Day, week (3) Blur time Midnightnoonteatime common options:-Q queue:at job queue;-f/path/from/somefile: reads the job to run from the specified file;-l: View a list of such running jobs in the job queue ; the equivalent of using the ATQ command;-c At_job_num: Look at the contents of the running job;-D: Deletes the specified job; equivalent to ATRM

Crontab: Recurring Task Scheduler daemon: Crond recurring tasks are available in two categories: (1)   system cron task; No user identity is run by default, so you need to specify the additional runner;/etc/crontabvim command # example  OF JOB DEFINITION:#&NBSP:---------------- minute  (0 - 59) # |   .------------- hour  (0 - 23) # |  |  .---------- day  of month  (1 - 31) # |  |  |  .------- month   (1 - 12)  or jan,feb,mar,apr ...# |  |  |  |  &NBSP:---- day of week  (0 - 6)   (sunday=0 or 7)  or  sun,mon,tue,wed,thu,fri,sat# |  |  |  |  |# *   *  *  *  * user-name  command to be  Executed7 fields: Top 5 fields: Point in time user-name:  run a task as a user command to be executed:  to run a task (2)   User Cron Task: Submitted by a user, run as submitter by default, so no additional designation is required/var/spool/cron/usernamevim command; crontab command: Suggested # example of job definition:# .----- ----------- minute  (0 - 59) # |  .------------- hour  (0 -  23) # |  |  .---------- day of month  (1 - 31) #  |  |  | &nbsp.------- month  (1 - 12)  or jan,feb, mar,apr ...# |  |  |  | &nbsp.---- day of week   (0 - 6)   (sunday=0 or 7)  OR sun,mon,tue,wed,thu,fri,sat# |   |  |  |  |# *  *  *  *  *   command to be executed5 time points: minutes: Valid range of values 0-59; Hours: 0-23 days: January-3 January: 1-12 weeks: 0-7 Note: The number of months and weeks, Not recommended for simultaneous use; For example: 6 * * * * time notation:*:  A specific continuous time range for each time point within the valid value range of the time point;-: ,  3-7, : A discrete point in time,  3,5,7/#: How many times in the effective time range;At the specified frequency;1-30/4, */45 */3 * * * /bin/echo  "Howdy" 5 7 * *  1-5 /bin/echo  "Howdy" crontab command: Crontab [-u user] [-l | -r | -e]-u  user:  is not managing its own cron task, but the specified target user's cron task; root only has permissions to manage other users ' cron tasks; By default,-l: list, list tasks;-r:  remove,  remove All Tasks;-e: edit, edit, open a default editor for the current shell session to edit the cron task table;

2, every Monday to Saturday 3:20 A.M., run the CP command to archive the/etc/directory, storage location is/BACKUPS/ETC-YYYY-MM-DD;

3 * * 1,6 cp-rp/etc/backups/etc-' date +%y-%m-%d '

3, every Sunday 2:30 A.M., run the CP command to backup the/etc/fstab file, the storage location is/BACKUP/FSTAB-YYYY-MM-DD-HH-MM-SS;

2 * * 0 cp/etc/fstab/backup/fstab-' date +%y-%m-%d-%h-%m-%s '

4, every night 12 o'clock, get all the lines in the/proc/meminfo file starting with S or M, appended to the/statistics/meminfo.txt file, and the daily message before, to add a similar =============== separator line;

0 * * * echo "=========================" >>/tmp/meminfo.txt | Egrep "^s|^m"/proc/meminfo >>/tmp/meminfo.txt

September 5, 2015-after-school assignments