Beyond Linux® From Scratch (systemd Edition) - Version r12.2-440

Chapter 12. System Utilities

at-3.2.5

Introduction to at

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

[Note]

Note

Development versions of BLFS may not build or run some packages properly if LFS or dependencies have been updated since the most recent stable versions of the books.

Package Information

at Dependencies

Required

An MTA

Optional

Linux-PAM-1.6.1

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