Manual page for CRON(8)
cron - clock daemon
SYNOPSIS
/usr/etc/cron
DESCRIPTION
cron
executes commands at specified dates and times.
Regularly scheduled commands can be specified according
to instructions found in
crontab
files in the directory
/var/spool/cron/crontabs.
Users can submit their own
crontab
files using the
crontab.1
command.
Commands that are to be executed only once may be
submitted using the
at.1
command.
cron
only examines
crontab
files and
at
command files during process
initialization and when a file changes using
crontab
or
at.
This reduces the overhead of checking for new or
changed files at regularly scheduled intervals.
Since
cron
never exits, it should only be executed once. This is normally done
by running
cron
from the initialization process through the file
/etc/rc;
see
init.8
/var/spool/cron/FIFO
is a
FIFO
file that
crontab
and
at
use to communicate with
cron;
it is also used as a lock file to prevent
the execution of more than one
cron.
FILES
- /var/spool/cron
-
main cron directory
- /var/spool/cron/FIFO
-
FIFO
for sending messages to
cron
- /var/spool/cron/crontabs
-
directory containing
crontab
files
SEE ALSO
at.1
crontab.1
sh.1
queuedefs.5
init.8
syslogd.8
DIAGNOSTICS
cron
logs various errors to the system log daemon,
syslogd.8
with a facility code of
cron.
The messages are listed here, grouped by severity level.
Err Severity
- Can't create /var/spool/cron/FIFO: reason
-
cron
was unable to start up because it could not create
/var/spool/cron/FIFO.
- Can't access /var/spool/cron/FIFO: reason
-
cron
was unable to start up because it could not access
/var/spool/cron/FIFO.
- Can't open /var/spool/cron/FIFO: reason
-
cron
was unable to start up because it could not open
/var/spool/cron/FIFO.
-
Can't start cron - another cron may be running (/var/spool/cron/FIFO exists)
-
cron
found that
/var/spool/cron/FIFO
already existed when it was started; this normally means that
cron
had already been started, but it may mean that an earlier
cron
terminated abnormally without removing
/var/spool/cron/FIFO.
- Can't stat /var/spool/cron/FIFO: reason
-
cron
could not get the status of
/var/spool/cron/FIFO.
- Can't change directory to directory:reason
-
cron
could not change to
directory.
- Can't read directory:reason
-
cron
could not read
directory.
- error reading message: reason
-
An error occurred when
cron
tried to read a control message from
/var/spool/cron/FIFO.
- message received -- bad format
-
A message was successfully read by
cron
from
/var/spool/cron/FIFO,
but the message was not of a form recognized by
cron.
- SIGTERM
-
received
cron
was told to terminate by having a
SIGTERM
signal sent to it.
- cron could not unlink /var/spool/cron/FIFO: reason
-
cron
was told to terminate, but it was unable to unlink
/var/spool/cron/FIFO
before it terminated.
- ******* CRON ABORTED ********
-
cron
terminated, either due to an error or because it was told to.
- Can't open queuedefs file file:reason
-
cron
could not open a
queuedefs
file.
- I/O error reading queuedefs file file:reason
-
An
I/O
error occurred while
cron
was reading a
queuedefs
file.
- Using default queue definitions
-
An error occurred while trying to read a
queuedefs
file; the default queue definitions will be used.
- Can't allocate numberbytes of space
-
An internal error occurred in
cron
while trying to allocate memory.
Info Severity
- queue queue max run limit reached
-
There were more jobs running or to be run in the queue
queue
than the maximum number specified.
cron
will wait until one of the currently-running jobs completes before
starting to run a new one.
- MAXRUN (25) procs reached
-
There were more than 25 jobs running or to be run by
cron.
cron
will wait until one of the currently-running jobs completes before
starting to run a new one.
- *** cron started ***
-
cron
started running.
- > CMD: pid queue command job
-
A
cron
job was started, in queue
queue,
with process
ID
pid.
command
is the command to be run.
For
at
or
batch
jobs,
job
is the job number.
- > user pid queue time job
-
A
cron
job was started for user
user,
in queue
queue,
with process
ID
pid,
at the date and time
time.
For
at
or
batch
jobs,
job
is the job number.
- < user pid queue time job status
-
A
cron
job completed for user
user,
in queue
queue,
with process
ID
pid,
at the date and time
time.
For
at
or
batch
jobs,
job
is the job number.
If the command terminated with a non-zero exit status or a signal,
status
indicates the exit status or signal.
Notice Severity
- Can't fork
-
An attempt to
fork (2)
to run a new job failed;
cron
will attempt again after a 30-second delay.
Warning Severity
- Can't stat queuedefs file file:reason
-
cron
could not get the status of a
queuedefs
file in order to determine whether it has changed.
cron
will assume it has changed and will reread it.
Created by unroff & hp-tools.
© somebody (See intro for details). All Rights Reserved.
Last modified 11/5/97