Summary
MongoDB 8.0+ crashes on startup on Linux kernel 6.19 and newer. mongod exits immediately with:
MongoDB cannot start: Linux kernel versions 6.19 and newer has a known incompatibility...
Root cause is an incompatibility between the new kernel's restartable-sequences (rseq) behavior and the TCMalloc vendored inside mongod. It affects all MongoDB 8.x packages — tarball, package managers, and Docker images alike.
Impact on this collection
The mongodb role deploys MongoDB 8 on Fedora CoreOS hosts. The kernel bump can land within a single FCOS major release, so pinning the FCOS major is not enough:
| FCOS build |
Kernel |
MongoDB 8 |
43.20260217.3.1 |
6.18 |
✅ works |
43.20260413.3.2 |
6.19 |
❌ broken |
Current handling
roles/mongodb/tasks/preflight.yml asserts the host kernel is < 6.19 (mongodb_unsupported_kernel) and fails fast with remediation guidance.- Bypass:
mongodb_skip_kernel_check: true (only after verifying mongo actually runs on the kernel — running with the check disabled on an incompatible kernel crashes containers in a tight loop).
- Documented in the
mongodb role README (Gotchas) and the top-level README troubleshooting section.
Upstream status (as of 2026-06)
Not fixed. MongoDB's production notes still carry the warning and only state that the issue will resolve "as soon as a patched version of TCMalloc is available." Releases through 8.2 still inherit the broken vendored TCMalloc, so upgrading forward does not escape it. (mongo:8.0.4 reportedly runs on newer kernels, but that is an older release predating the bad TCMalloc bump, not a forward fix.)
A community-confirmed workaround omitted from the official docs: setting GLIBC_TUNABLES=glibc.pthread.rseq=0 in the container environment lets mongod 8.x run on kernel 6.19+.
Action items
References
Summary
MongoDB 8.0+ crashes on startup on Linux kernel 6.19 and newer.
mongodexits immediately with:Root cause is an incompatibility between the new kernel's restartable-sequences (rseq) behavior and the TCMalloc vendored inside mongod. It affects all MongoDB 8.x packages — tarball, package managers, and Docker images alike.
Impact on this collection
The
mongodbrole deploys MongoDB 8 on Fedora CoreOS hosts. The kernel bump can land within a single FCOS major release, so pinning the FCOS major is not enough:43.20260217.3.143.20260413.3.2Current handling
roles/mongodb/tasks/preflight.ymlasserts the host kernel is< 6.19(mongodb_unsupported_kernel) and fails fast with remediation guidance.mongodb_skip_kernel_check: true(only after verifying mongo actually runs on the kernel — running with the check disabled on an incompatible kernel crashes containers in a tight loop).mongodbrole README (Gotchas) and the top-level README troubleshooting section.Upstream status (as of 2026-06)
Not fixed. MongoDB's production notes still carry the warning and only state that the issue will resolve "as soon as a patched version of TCMalloc is available." Releases through 8.2 still inherit the broken vendored TCMalloc, so upgrading forward does not escape it. (
mongo:8.0.4reportedly runs on newer kernels, but that is an older release predating the bad TCMalloc bump, not a forward fix.)A community-confirmed workaround omitted from the official docs: setting
GLIBC_TUNABLES=glibc.pthread.rseq=0in the container environment lets mongod 8.x run on kernel 6.19+.Action items
mongodb_unsupported_kernelonce verified.GLIBC_TUNABLES=glibc.pthread.rseq=0workaround as an opt-in role variable.References