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Chapter 8. Known Issues
This chapter documents known problems in Red Hat Enterprise Linux 7.9.
8.1. Authentication and Interoperability Copia collegamentoCollegamento copiato negli appunti!
Trusts with Active Directory do not work properly after upgrading ipa-server using the latest container image
After upgrading an IdM server with the latest version of the container image, existing trusts with Active Directory domains no longer work. To work around this problem, delete the existing trust and re-establish it after the upgrade.
Potential risk when using the default value for ldap_id_use_start_tls option
When using
ldap://
Currently, the SSSD configuration option to enforce TLS,
ldap_id_use_start_tls
false
id_provider = ldap
id_provider = ad
id_provider = ipa
If it is not safe to use unencrypted communication, enforce TLS by setting the
ldap_id_use_start_tls
true
/etc/sssd/sssd.conf
(JIRA:RHELPLAN-155168)
8.2. Compiler and Tools Copia collegamentoCollegamento copiato negli appunti!
GCC thread sanitizer included in RHEL no longer works
Due to incompatible changes in kernel memory mapping, the thread sanitizer included with the GNU C Compiler (GCC) compiler version in RHEL no longer works. Additionally, the thread sanitizer cannot be adapted to the incompatible memory layout. As a result, it is no longer possible to use the GCC thread sanitizer included with RHEL.
As a workaround, use the version of GCC included in Red Hat Developer Toolset to build code which uses the thread sanitizer.
(BZ#1569484)
8.3. Installation and Booting Copia collegamentoCollegamento copiato negli appunti!
Systems installed as Server with GUI with the DISA STIG profile or with the CIS profile do not start properly
The DISA STIG profile and the CIS profile require the removal of the
xorg-x11-server-common
Server with GUI
package_xorg-x11-server-common_removed
8.4. Kernel Copia collegamentoCollegamento copiato negli appunti!
The radeon driver fails to reset hardware correctly when performing kdump
When booting the kernel from the currently running kernel, such as when performing the kdump process, the
radeon
To work around this problem, disable
radeon
/etc/kdump.conf
dracut_args --omit-drivers "radeon"
Afterwards, restart the machine and kdump.
Note that in this scenario, no graphics will be available during kdump, but kdump will complete successfully.
(BZ#1168430)
Slow connection to RHEL 7 guest console on a Windows Server 2019 host
When using RHEL 7 as a guest operating system in multi-user mode on a Windows Server 2019 host, connecting to a console output of the guest currently takes significantly longer than expected. To work around this problem, connect to the guest using SSH or use Windows Server 2016 as the host.
(BZ#1706522)
Kernel deadlocks can occur when dm_crypt is used with intel_qat
The
intel_qat
GFP_ATOMIC
dm_crypt
intel_qat
- Update to RHEL 8
-
Avoid using for encryption offload (potential performance impact)
intel_qat - Ensure the system does not get under excessive memory pressure
(BZ#1813394)
The vmcore file generation fails on Amazon c5a machines on RHEL 7
On Amazon c5a machines, the Advanced Programmable Interrupt Controller (APIC) fails to route the interrupts of the Local APIC (LAPIC), when configured in the
flat mode
kdump
kdump
kdump
vmcore
To work around the problem:
Increase the crash kernel size by setting the
argument tocrashkernel:256M$ grubby-args="crashkernel=256M" --update-kernel /boot/vmlinuz-`uname -r`Set the
option by editing thenr_cpus=9file:/etc/sysconfig/kdumpKDUMP_COMMANDLINE_APPEND="irqpoll" *nr_cpus=9* reset_devices cgroup_disable=memory mce=off numa=off udev.children- max=2 panic=10 acpi_no_memhotplug transparent_hugepage=never nokaslr novmcoredd hest_disable
As a result, the
kdump
vmcore
kdump
vmcore
kdump
kdump
(BZ#1844522)
Enabling some kretprobes can trigger kernel panic
Using
kretprobes
-
_raw_spin_lock -
_raw_spin_lock_irqsave -
_raw_spin_unlock_irqrestore -
queued_spin_lock_slowpath
As a consequence, enabling these
kprobe
kretprobes
(BZ#1838903)
The kdump service fails on UEFI Secure Boot enabled systems
If a UEFI Secure Boot enabled system boots with a not up-to-date RHEL kernel version, the
kdump
kdump
kexec_file_load failed: Required key not available
This behavior displays due to either of these:
- Booting the crash kernel with a not up-to-date kernel version.
-
Configuring the variable in
KDUMP_KERNELVERfile to a not up-to-date kernel version./etc/sysconfig/kdump
As a consequence,
kdump
To workaround this problem, use either of these:
- Boot the crash kernel with the latest RHEL 7 fixes.
-
Configure in
KDUMP_KERNELVERto use the latest kernel version.etc/sysconfig/kdump
As a result,
kdump
(BZ#1862840)
The RHEL installer might not detect iSCSI storage
The RHEL installer might not automatically set kernel command-line options related to iSCSI for some offloading iSCSI host bus adapters (HBAs). As a consequence, the RHEL installer might not detect iSCSI storage.
To work around the problem, add the following options to the kernel command line when booting to the installer:
rd.iscsi.ibft=1 rd.iscsi.firmware=1
These options enable network configuration and iSCSI target discovery from the pre-OS firmware configuration.
The firmware configures the iSCSI storage, and as a result, the installer can discover and use the iSCSI storage.
(BZ#1871027)
Race condition in the mlx5e_rep_neigh_update work queue sometimes triggers the kernel panic
When offloading encapsulation actions over the
mlx5
switchdev
mlx5e_rep_neigh_update
Workqueue: mlx5e mlx5e_rep_neigh_update [mlx5_core]
Currently, a workaround or partial mitigation to this problem is not known.
(BZ#1874101)
The ice driver does not load for Intel® network adapters
The
ice
-
v00008086d00001593sv*sd*bc*sc*i* -
v00008086d00001592sv*sd*bc*sc*i* -
v00008086d00001591sv*sd*bc*sc*i*
Consequently, the network adapter remains undetected by the operating system. To work around this problem, you can use external drivers for RHEL 7 provided by Intel® or Dell.
(BZ#1933998)
kdump does not support setting nr_cpus to 2 or higher in Hyper-V virtual machines
When using RHEL 7.9 as a guest operating system on a Microsoft Hyper-V hypervisor, the kdump kernel in some cases becomes unresponsive when the
nr_cpus
nr_cpus=1
/etc/sysconfig/kdump
8.5. Networking Copia collegamentoCollegamento copiato negli appunti!
Verification of signatures using the MD5 hash algorithm is disabled in Red Hat Enterprise Linux 7
It is impossible to connect to any Wi-Fi Protected Access (WPA) Enterprise Access Point (AP) that requires MD5 signed certificates. To work around this problem, copy the
wpa_supplicant.service
/usr/lib/systemd/system/
/etc/systemd/system/
Environment=OPENSSL_ENABLE_MD5_VERIFY=1
Then run the
systemctl daemon-reload
Note that MD5 certificates are highly insecure and Red Hat does not recommend using them.
(BZ#1062656)
bind-utils DNS lookup utilities support fewer search domains than glibc
The
dig
host
nslookup
bind-utils
glibc
/etc/resolv.conf
To work around this problem, use one of the following:
- Full names ending with a dot, or
-
Fewer than nine domains in the search clause.
resolv.conf
Note that it is not recommended to use more than three domains.
BIND 9.11 changes log severity of query errors when query logging is enabled
With the BIND 9.11 update, the log severity for the
query-errors
debug 1
info
logging
/etc/named.conf
category query-errors { default_debug; };
This will move query errors back into the debug log.
Alternatively, use the following statement to discard all query error messages:
category querry-errors { null; };
As a result, only name queries are logged in a similar way to the previous BIND 9.9.4 release.
(BZ#1853191)
named-chroot service fails to start when check-names option is not allowed in forward zone
Previously, the usage of the
check-names
forward zone
With the rebase to
bind
zone
-
master -
slave -
stub -
hint
use the
check-names
Consequently, the
check-names
forward zone
named-chroot
check-names
zone
master
slave
stub
hint
As a result, the
named-chroot
(BZ#1851836)
The NFQUEUE target overrides queue-cpu-fanout flag
iptables
NFQUEUE
--queue-bypass
--queue-cpu-fanout
--queue-cpu-fanout
--queue-bypass
--queue-cpu-fanout
To work around this problem, rearrange the
--queue-bypass
--queue-cpu-fanout
8.6. Security Copia collegamentoCollegamento copiato negli appunti!
Audit executable watches on symlinks do not work
File monitoring provided by the
-w
To work around the problem, set up a watch for the resolved path of the program executable, and filter the resulting log messages using the last component listed in the
comm=
proctitle=
(BZ#1421794)
Executing a file while transitioning to another SELinux context requires additional permissions
Due to the backport of the fix for CVE-2019-11190 in RHEL 7.8, executing a file while transitioning to another SELinux context requires more permissions than in previous releases.
In most cases, the
domain_entry_file()
If the problem occurs on the file from the domain which is a part of the
selinux-policy
-
for shell scripts
corecmd_exec_shell() -
for interpreters labeled as
corecmd_exec_all_executables()such as Perl or Pythonbin_t
For more details, see the
/usr/share/selinux/devel/include/kernel/corecommands.if
selinux-policy-doc
(BZ#1832194)
Scanning large numbers of files with OpenSCAP causes systems to run out of memory
The OpenSCAP scanner stores all collected results in the memory until the scan finishes. As a consequence, the system might run out of memory on systems with low RAM when scanning large numbers of files, for example, from the large package groups Server with GUI and Workstation.
To work around this problem, use smaller package groups, for example, Server and Minimal Install on systems with limited RAM. If your scenario requires large package groups, you can test whether your system has sufficient memory in a virtual or staging environment. Alternatively, you can tailor the scanning profile to deselect rules that involve recursion over the entire
/
-
rpm_verify_hashes -
rpm_verify_permissions -
rpm_verify_ownership -
file_permissions_unauthorized_world_writable -
no_files_unowned_by_user -
dir_perms_world_writable_system_owned -
file_permissions_unauthorized_suid -
file_permissions_unauthorized_sgid -
file_permissions_ungroupowned -
dir_perms_world_writable_sticky_bits
This prevents the OpenSCAP scanner from causing the system to run out of memory.
RSA signatures with SHA-1 cannot be completely disabled in RHEL7
Because the
ssh-rsa
rsa-sha2-512
rsa-sha2-256
rpm_verify_permissions fails in the CIS profile
The
rpm_verify_permissions
scap-security-guide
rpm_verify_permissions
-
(0700)
/etc/cron.d -
(0700)
/etc/cron.hourly -
(0700)
/etc/cron.monthly -
(0600)
/etc/crontab -
(0700)
/etc/cron.weekly -
(0700)
/etc/cron.daily
For more information about the related feature, see SCAP Security Guide now provides a profile aligned with the CIS RHEL 7 Benchmark v2.2.0.
OpenSCAP file ownership-related rules do not work with remote user and group back ends
The OVAL language used by the OpenSCAP suite to perform configuration checks has a limited set of capabilities. It lacks possibilities to obtain a complete list of system users, groups, and their IDs if some of them are remote. For example, if they are stored in an external database such as LDAP.
As a consequence, rules that work with user IDs or group IDs do not have access to IDs of remote users. Therefore, such IDs are identified as foreign to the system. This might result in scans to fail on compliant systems. In the
scap-security-guide
-
xccdf_org.ssgproject.content_rule_file_permissions_ungroupowned -
xccdf_org.ssgproject.content_rule_no_files_unowned_by_user
To work around this problem, if a rule that deals with user or group IDs fails on a system that defines remote users, check the failed parts manually. The OpenSCAP scanner enables you to specify the
--oval-results
--report
Additionally, in RHEL 8.3, the rules in the
scap-security-guide
rpm_verify_permissions and rpm_verify_ownership fail in the Essential Eight profile
The
rpm_verify_permissions
rpm_verify_ownership
scap-security-guide
rpm_verify_permissions
rpm_verify_ownership
/usr/libexec/abrt-action-install-debuginfo-to-abrt-cache
root
suid
sgid
8.7. Servers and Services Copia collegamentoCollegamento copiato negli appunti!
The compat-unixODBC234 package for SAP requires a symlink to load the unixODBC library
The
unixODBC
compat-unixODBC234
sap-hana
compat-unixODBC234 for SAP for details.
Due to minor ABI differences between
unixODBC
compat-unixODBC234
/usr/lib64/libodbc.so.1002.0.0
/usr/lib64/libodbc.so.2.0.0
As a consequence, third party applications built with
unixODBC
unixODBC
dlopen()
/usr/lib64/libodbc.so.2.0.0: cannot open shared object file: No such file or directory
To work around this problem, create the following symbolic link:
# ln -s /usr/lib64/libodbc.so.1002.0.0 /usr/lib64/libodbc.so.2.0.0
and similar symlinks for other libraries from the
compat-unixODBC234
Note that the
compat-unixODBC234
unixODBC
unixODBC
compat-unixODBC234
(BZ#1844443)
Symbol conflicts between OpenLDAP libraries might cause crashes in httpd
When both the
libldap
libldap_r
httpd
ldap
mod_security
mod_auth_openidc
httpd
With this update to the Apache Portable Runtime (APR) library, you can work around the problem by setting the
APR_DEEPBIND
RTLD_DEEPBIND
httpd
APR_DEEPBIND
httpd
(BZ#1739287)
8.8. Storage Copia collegamentoCollegamento copiato negli appunti!
RHEL 7 does not support VMD 2.0 storage
The 10th generation Intel Core and 3rd generation Intel Xeon Scalable platforms (also known as Intel Ice Lake) include hardware that utilizes version 2.0 of the Volume Management Device (VMD) technology.
RHEL 7 no longer receives updates to support new hardware. As a consequence, RHEL 7 cannot recognize Non-Volatile Memory Express (NVMe) devices that are managed by VMD 2.0.
To work around the problem, Red Hat recommends that you upgrade to a recent major RHEL release.
(BZ#1942865)
SCSI devices cannot be deleted after removing the iSCSI target
If a SCSI device is
BLOCKED
delete sysfs
/sys/block/sd*/device/delete
To work around this issue, terminate the transport session with the
iscsiadm logout
(BZ#1439055)
8.9. System and Subscription Management Copia collegamentoCollegamento copiato negli appunti!
The needs-restarting command from yum-utils might fail to display the container boot time
In certain RHEL 7 container environments, the
needs-restarting
yum-utils
8.10. Virtualization Copia collegamentoCollegamento copiato negli appunti!
RHEL 7.9 virtual machines on IBM POWER sometimes do not detect hot-plugged devices
RHEL7.9 virtual machines (VMs) started on an IBM POWER system on a RHEL 8.3 or later hypervisor do not detect hot-plugged PCI devices if the hot plug is performed when the VM is not fully booted yet. To work around the problem, reboot the VM.
(BZ#1854917)
8.11. RHEL in cloud environments Copia collegamentoCollegamento copiato negli appunti!
Core dumping RHEL 7 virtual machines that use NICs with enabled accelerated networking to a remote machine on Azure fails
Currently, using the
kdump
kdump
To prevent this problem from occurring, add the following line to the
/etc/kdump.conf
kdump
extra_modules pci_hyperv
(BZ#1846667)
SSH with password login now impossible by default on RHEL 8 virtual machines configured using cloud-init
For security reasons, the
ssh_pwauth
cloud-init
0
cloud-init
If you require using a password login for SSH connections to your RHEL 8 VMs configured using
cloud-init
ssh_pwauth: 1
(BZ#1685580)