install-cron - Schedule Automated Tasks

The install-cron command creates a cron job in the current user’s crontab. It supports two job types: scheduled update checks (check) and automated binary self-updates (self-update).

Usage

update-watcher install-cron [--type TYPE] [--time HH:MM] [--cron-expr "EXPR"]

Flags

Default Behavior

update-watcher install-cron

This adds the following entry to the current user’s crontab:

# update-watcher scheduled check
0 7 * * * /usr/local/bin/update-watcher run --quiet 2>&1 | logger -t update-watcher

The entry includes an identifying comment that is used by the uninstall-cron command to locate and remove it.

Examples

Daily at a Custom Time

Run the check every day at 9:30 AM:

update-watcher install-cron --time 09:30

Custom Cron Expression

Run twice daily at 7:00 AM and 7:00 PM:

update-watcher install-cron --cron-expr "0 7,19 * * *"

Run every Monday at 6:00 AM:

update-watcher install-cron --cron-expr "0 6 * * 1"

Automated Self-Update

Schedule a weekly self-update every Sunday at 3:00 AM:

update-watcher install-cron --type self-update --cron-expr "0 3 * * 0"

This keeps the binary up to date automatically. The self-update job runs independently from the check job.

Both Jobs Together

Install a daily check and a weekly self-update:

update-watcher install-cron --time 07:00
update-watcher install-cron --type self-update --cron-expr "0 3 * * 0"

Verify the Cron Jobs

After installation, verify the entries exist in your crontab:

crontab -l

You should see:

# update-watcher scheduled check
0 7 * * * /usr/local/bin/update-watcher run --quiet 2>&1 | logger -t update-watcher
# update-watcher self-update
0 3 * * 0 /usr/local/bin/update-watcher self-update 2>&1 | logger -t update-watcher

How It Works

The install-cron command modifies the current user’s crontab using the crontab utility:

1. Reads the existing crontab.
2. Checks for an existing entry of the same job type (by the identifying comment).
3. If an entry exists, replaces it with the new schedule.
4. If no entry exists, appends the new cron entry.
5. Writes the updated crontab.

Each job type has its own comment marker, so check and self-update jobs are managed independently. The command is idempotent. Running it multiple times updates the schedule rather than creating duplicate entries.

Dedicated Service User

On Linux servers with a dedicated update-watcher user, install the cron job under that user’s crontab:

sudo crontab -u update-watcher -e

And add manually:

# update-watcher scheduled check
0 7 * * * /usr/local/bin/update-watcher run --quiet --as-service-user 2>&1 | logger -t update-watcher

Alternatively, use the install-cron command while running as the service user:

sudo -u update-watcher update-watcher install-cron

For complete server setup instructions, see Linux Server Setup.

Updating the Schedule

To change the schedule, simply run install-cron again with the same --type and new time or expression. The existing entry is replaced:

# Originally set to 07:00
update-watcher install-cron --time 07:00

# Later changed to 09:00
update-watcher install-cron --time 09:00

Related

• uninstall-cron – Remove cron jobs.
• self-update – Update the binary manually.
• Cron Scheduling – Detailed cron scheduling guide with logging and verification.
• Linux Server Setup – Production-ready server setup with dedicated user and cron.