CentOS/RHEL 7

Problem /tmp is not automatically mounted after reboot even though an entry is present in /etc/fstab. Below outputs show an example of the issue: # uptime 16:44:11 up 2 min, 1 user, load average: 0.21, 0.55, 0.44 # df -h Filesystem Size Used Avail Use% Mounted on devtmpfs 252G 0 252G 0% /dev tmpfs 252G […]

This post will show how to Disable the HMAC MD5 and the CBC ciphers as an example for CentOS/RHEL 6 and 7. For CentOS/RHEL 7 For more information please look at the man pages: # man sshd_config Ciphers Specifies the ciphers allowed. Multiple ciphers must be comma-separated. If the specified value begins with a ‘+’ […]

This post will help to disable TLS 1.1 cockpit port 9090. 1. Create file /etc/systemd/system/cockpit.service.d/ssl.conf containing: [Service] Environment=G_TLS_GNUTLS_PRIORITY=NORMAL:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1 2. Reload systemd daemons: # systemctl daemon-reload 3. Restart cockpit service: # systemctl restart cockpit 4. Check protocols tls1_1: # echo test | openssl s_client -connect localhost:9090 -tls1_1CONNECTED(00000003) 139687924594576:error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number:s3_pkt.c:365: — no peer certificate available […]

Access to certain ports are blocked or dropped by firewalld unless added to a firewall zone. This post outlines steps to add source, service, and ports to the firewall zones in CentOS/RHEL 7 and 8 systems. Adding Service to Firewall Zone Adding a service to a zone is the simplest way to configure the firewall. […]

The Problem rpc.statd(or rpc.*) logs following error messages into syslog(/var/log/messages): Nov 29 11:01:34 hostname rpc.statd[12345]: Failed to create listener xprt (statd, 1, udp6) Nov 29 11:01:34 hostname rpc.statd[12345]: Failed to create listener xprt (statd, 1, tcp6) Or you can also check the rpc-statd.service status: # systemctl status rpc-statd.service ● rpc-statd.service – NFS status monitor for […]

Question: How to configure CIFS debug option in Linux servers to provide additional debug information in the client system logs? 1. Take backup of existing debug or to check the default value: # cp /sys/kernel/debug/dynamic_debug/control /root/backup # cat /proc/fs/cifs/cifsFYI # cat /proc/fs/cifs/traceSMB 2. Enable debug chosen options: # echo ‘module cifs +p’ > /sys/kernel/debug/dynamic_debug/control # […]

Question: How to debug/find, changes or failing commands during boot process? During boot process, when seeing grub boot menu press “e” for edit the grub, then scroll down until you see boot entry: echo “Loading Linux… linux16 /vmlinuz-XXX root=XXXro crashkernel=auto rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet LANG=en_US.UTF-8 On the line with “linux” remove the following entries if […]

The Problem After replacing issue disk on software RAID, mdadm Fails to Start the RAID Array with Error – “not enough to start the array” and Software Raid State is showing “active, FAILED, Not Started” “mdadm –detail /dev/md0” showing only 4 disks are active and 8 removed disks. # mdadm –detail /dev/md0 State : active, […]

The Problem How to remove an LVM volume which returns “filesystem in use” error. # lvchange -an /dev/mapper/vg-lv Logical volume vg/lv contains a filesystem in use The Solution Step 1: Try to identify if this particular LVM is mounted in your server. # mount -a | grep /path-to-LV-volume If mounted, unmount it. Step 2: Check […]