apport information ** Tags added: apport-collected noble wayland-session
** Description changed: Summary Nautilus cannot generate file thumbnails on a fresh Ubuntu 24.04 installation. The issue is caused by AppArmor restricting unprivileged user namespaces, which prevents bubblewrap (bwrap) from creating the sandbox environment required by the thumbnail generation process. Disabling the AppArmor user namespace restriction fixes the issue immediately. Environment - OS: Ubuntu 24.04 LTS (Noble Numbat) - Desktop: GNOME - Nautilus version: 46.4 - Architecture: amd64 - Kernel: Linux 7.0.0-28-generic #28~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC - bubblewrap: bubblewrap 0.9.0-1ubuntu0.1 - AppArmor: 4.0.1really4.0.1-0ubuntu0.24.04.7 Steps to reproduce 1. Install a fresh Ubuntu 24.04 system. 2. Open Nautilus. 3. Navigate to a directory containing images/videos. 4. Enable thumbnail display. 5. Thumbnails are not generated. Expected behavior Nautilus should generate thumbnails normally on a default Ubuntu desktop installation. Actual behavior Nautilus fails to generate thumbnails. The kernel log shows bubblewrap failing due to AppArmor restrictions: apparmor="DENIED" profile="unprivileged_userns" comm="bwrap" capname="setpcap" apparmor="DENIED" profile="unprivileged_userns" name="proc/<pid>/uid_map" requested_mask="wr" Running bubblewrap manually reproduces the problem: $ bwrap --ro-bind / / true bwrap: setting up uid map: Permission denied Additional investigation The following checks were performed: User namespaces are enabled: $ cat /proc/sys/kernel/unprivileged_userns_clone 1 User namespace limit is sufficient: $ sysctl user.max_user_namespaces user.max_user_namespaces = 115486 Subuid/subgid configuration exists: $ cat /etc/subuid nfl-jiancx:100000:65536 $ cat /etc/subgid nfl-jiancx:100000:65536 Disabling AppArmor user namespace restriction fixes the issue: $ sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0 After this change: $ unshare --user --map-root-user id uid=0(root) gid=0(root) $ bwrap --unshare-user --uid 0 --gid 0 true works correctly. Nautilus thumbnails immediately start working again. Possible cause Ubuntu 24.04 enables: kernel.apparmor_restrict_unprivileged_userns=1 by default. This appears to prevent bubblewrap from creating the user namespace required by GNOME thumbnail generation. Suggested fix Possible solutions: 1. Allow bubblewrap thumbnail sandbox usage under the AppArmor policy. or 2. Adjust the Ubuntu default AppArmor/user namespace policy so GNOME desktop components depending on bubblewrap continue to work. - A fresh Ubuntu desktop installation should not require users to manually - disable AppArmor restrictions or set SUID on /usr/bin/bwrap to get - Nautilus thumbnails working. + A fresh Ubuntu desktop installation should not require users to manually disable AppArmor restrictions or set SUID on /usr/bin/bwrap to get Nautilus thumbnails working. + --- + ProblemType: Bug + ApportVersion: 2.28.2-0ubuntu0.1 + Architecture: amd64 + CasperMD5CheckResult: unknown + CurrentDesktop: ubuntu:GNOME + DistroRelease: Ubuntu 24.04 + GsettingsChanges: + b'org.gnome.nautilus.icon-view' b'default-zoom-level' b"'medium'" + b'org.gnome.nautilus.list-view' b'default-column-order' b"['name', 'size', 'type', 'owner', 'group', 'permissions', 'date_modified', 'date_accessed', 'date_created', 'recency', 'detailed_type']" + b'org.gnome.nautilus.preferences' b'default-folder-viewer' b"'list-view'" + b'org.gnome.nautilus.preferences' b'migrated-gtk-settings' b'true' + b'org.gnome.nautilus.window-state' b'initial-size' b'(873, 533)' + InstallationDate: Installed on 2026-06-20 (40 days ago) + InstallationMedia: Ubuntu 24.04.4 LTS "Noble Numbat" - Release amd64 (20260210) + Package: nautilus 1:46.4-0ubuntu0.2 + PackageArchitecture: amd64 + ProcEnviron: + LANG=zh_CN.UTF-8 + PATH=(custom, no user) + SHELL=/bin/bash + TERM=xterm-256color + XDG_RUNTIME_DIR=<set> + ProcVersionSignature: Ubuntu 7.0.0-28.28~24.04.1-generic 7.0.12 + Tags: noble wayland-session + Uname: Linux 7.0.0-28-generic x86_64 + UpgradeStatus: No upgrade log present (probably fresh install) + UserGroups: adm cdrom dip lpadmin plugdev sudo users + _MarkForUpload: True + usr_lib_nautilus: + file-roller 44.3-0ubuntu2 + nautilus-extension-gnome-terminal 3.52.0-1ubuntu2 ** Attachment added: "Dependencies.txt" https://bugs.launchpad.net/bugs/2162114/+attachment/5987904/+files/Dependencies.txt -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2162114 Title: Nautilus thumbnails fail to generate on Ubuntu 24.04 due to AppArmor restricting bubblewrap user namespaces To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/nautilus/+bug/2162114/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
