Beyond Linux® From Scratch (systemd Edition) - Version 11.3

Chapter 12. System Utilities

at-3.2.5

Introduction to at

The at package provide delayed job execution and batch processing. It is required for Linux Standards Base (LSB) conformance.

This package is known to build and work properly using an LFS 11.3 platform.

Package Information

at Dependencies

Required

An MTA

Optional

Linux-PAM-1.5.2

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/at

Installation of at

Before building at, as the root user you should create the group and user atd which will run the atd daemon: 

groupadd -g 17 atd                                                  &&
useradd -d /dev/null -c "atd daemon" -g atd -s /bin/false -u 17 atd

Install at with the following commands: 

./configure --with-daemon_username=atd        \
            --with-daemon_groupname=atd       \
            SENDMAIL=/usr/sbin/sendmail       \
            --with-jobdir=/var/spool/atjobs   \
            --with-atspool=/var/spool/atspool \
            --with-systemdsystemunitdir=/lib/systemd/system &&
make -j1

To test the results, issue: make test.

Now, as the root user: 

make install docdir=/usr/share/doc/at-3.2.5 \
             atdocdir=/usr/share/doc/at-3.2.5

Configuring at

Config Files

/etc/at.allow and /etc/at.deny determines who can submit jobs via at or batch.

Linux PAM Configuration

If At has been built with Linux PAM support, you need to create a PAM configuration file, to get it working correctly with BLFS.

Issue the following commands as the root user to create the configuration file for Linux PAM: 

cat > /etc/pam.d/atd << "EOF"
# Begin /etc/pam.d/atd

auth required pam_unix.so
account required pam_unix.so
password required pam_unix.so
session required pam_unix.so

# End /etc/pam.d/atd
EOF

Systemd Unit

To start the atd daemon at boot, enable the previously installed systemd unit by running the following command as the root user: 

systemctl enable atd

Contents

Installed Programs: at, atd, atq (symlink), atrm (symlink), atrun, and batch
Installed Libraries: None
Installed Directories: /usr/share/doc/at-3.2.5

Short Descriptions

at

queues, examines or deletes jobs for later execution

atd

is the daemon that runs jobs queued for later execution

atq

lists the user's pending jobs, or all jobs, if superuser

atrm

deletes jobs, identified by their job number

atrun

runs jobs queued for later execution

batch

is a script that executes commands when system load levels permit