Public bug reported:
Bug Report: cupsd.conf corrupted during automatic update with EOF marker left
in file
Description
During an automatic system update via unattended-upgrades, the
/etc/cups/cupsd.conf configuration file became corrupted. The file
contained a literal EOF marker on line 53, which caused the CUPS service
to fail with the error: "Unable to read /etc/cups/cupsd.conf due to
errors."
The CUPS service would not start, resulting in complete printing unavailability
until the configuration file was manually repaired.
Steps to Reproduce
Have a working Ubuntu system with CUPS installed and automatic updates
enabled
Wait for unattended-upgrades to perform automatic updates (timing may vary)
After update, attempt to start CUPS service: sudo systemctl start cups
Observe failure with error in logs
Note: This appears to be an intermittent issue related to the package update
process, not easily reproducible on demand.
Expected Behavior
CUPS configuration files should be preserved or properly merged during
updates
The service should continue to work after automatic updates
No stray markers or corrupted syntax in configuration files
Actual Behavior
cupsd.conf contained EOF as actual content on line 53
CUPS service fails to start with configuration syntax error
Manual intervention required to restore printing functionality
System Information
OS: Ubuntu 24.04.3 LTS (noble)
CUPS Version: 2.4.7-1.2ubuntu7.7 (main cups package)
Related Packages:
cups-common: 2.4.7-1.2ubuntu7.7
cups-daemon: 2.4.7-1.2ubuntu7.7
cups-core-drivers: 2.4.7-1.2ubuntu7.7
Update Method: unattended-upgrades with default configuration
Automatic Updates: Enabled (APT::Periodic::Unattended-Upgrade "1")
Configuration File Error
The corrupted file ended with:
EOF ```
The EOF marker (typically used in shell heredoc syntax) was written as literal
content in the configuration file, causing a syntax error.
Error Messages from Logs
From journalctl -xeu cups.service:
Dez 03 14:42:31 nuc cupsd[1750]: Unable to read "/etc/cups/cupsd.conf" due to
errors.
Dez 03 14:42:31 nuc systemd[1]: cups.service: Main process exited, code=exited,
status=1/FAILURE
Impact
Severity: Medium-High (printing completely unavailable)
Frequency: Intermittent (depends on update timing)
Workaround: Manual restoration of configuration file from backup
Affected Users: All users with automatic updates enabled and CUPS
installed
Workaround/Fix Applied
Removed the stray EOF line from /etc/cups/cupsd.conf
Verified configuration with sudo cupsd -t
Restarted CUPS service
Root Cause Analysis
Most likely caused by:
A failed or interrupted configuration file merge during package update
Race condition in configuration file handling during dpkg post-
installation scripts
Issue with configuration file templates or update scripts in the CUPS
package (specifically cups-common or cups-daemon)
Suggestions for Fix
Validation: Add configuration file validation in post-install scripts
Backup: Automatic backup of working configuration before updates
Recovery: Automatic fallback to previous configuration if new one fails
validation
Logging: Better error reporting when configuration updates fail
Safe Write: Use atomic file operations for configuration updates
Additional Information
Original working configuration was backed up as
/etc/cups/cupsd.conf.backup
Error was consistent and reproducible on the affected system until
manually fixed
System logs showed repeated restart attempts by systemd before manual
intervention
Complete CUPS package list from affected system:
cups: 2.4.7-1.2ubuntu7.7
cups-common: 2.4.7-1.2ubuntu7.7
cups-daemon: 2.4.7-1.2ubuntu7.7
cups-core-drivers: 2.4.7-1.2ubuntu7.7
Related Issues
Possibly related to configuration file handling in package managers
May affect other services with complex configuration files during
automatic updates
Could be specific to the cups-common package update process
Reproduction Rate: Intermittent (appears to be timing/race-condition dependent)
Priority: Medium (breaks core printing functionality but has workaround)
Regression Risk: Low (fix would improve robustness)
## This is an Ubuntu/Debian packaging issue
The problem appears to be in the post-installation scripts (`postinst`) of the
`cups-common` package, not in CUPS itself. During automatic updates via
`unattended-upgrades`, the configuration file merge process fails and leaves
stray EOF markers in the configuration file.
## Likely Trigger
The error seems to occur when:
1. `unattended-upgrades` installs CUPS updates
2. The `cups-common.postinst` script runs
3. Something interrupts or fails during configuration file merging
4. Result: `/etc/cups/cupsd.conf` contains literal "EOF"
** Affects: cups (Ubuntu)
Importance: Undecided
Status: New
** Tags: cups
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https://bugs.launchpad.net/bugs/2133850
Title:
cupsd.conf corrupted during unattended-upgrades with EOF marker in
file
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