These are the objectives Understand and use essential tools Access a shell prompt and issue commands with correct syntax Use input-output redirection (>, >>, |, 2>, etc.) Use grep and regular expressions to analyze text Access remote systems using SSH…
Category: RedHat
server time off, due to hardware clock out of sync
On reboot the server time can be out of sync, because hard clock is out of sync. This can be checked by running”hwclock; date” and comparing the results. In Red Hat 6, the ntpdate start-up script is is separate from…
How to get CORRECT memory usage for Linux
One of the most common mistakes made by Linux users, is to run free (Mem: line) or sar to get memory utilization. The memory used fields include the space used by the OS to cache files and directory info cace,…
Sar Grapher Updated
Sar Grapher has been updated. It now graphs Linux NFS Server performance data.
Lunix Core Files
To enable core file generation.. Configure core files to use the PID as a extension. Set “kernel.core_uses_pid = 1” in /etc/sysctl.conf and run “/sbin/sysctl -p /etc/sysctl.conf: or to add it temporarily run “/sbin/sysctl -w kernel.core_uses_pid=1” to change the running kernel. …
How to Reduce/Shrink a ext[234] File System
In order to shrink a file system, the file system must be unmounted. For example with a LVM Logical volume called testfilesystem in volume group testVG mount on /opt/testfilesystem ( /dev/testVG-testfilesystem or /dev/mapper/testVG-testfilesystem) that we want to make 162 GB in sise. First…
Listing Full RPM Package Name
To get a full list RPM name, like the RPM file name use the Query Format option (–qf or –queryformat). This is useful in comparing 2 systems, seeing 32 bit and 64 bit packages and finding the RPMs. This lists…
Mapping SCSI Disks
Identify scsi disk Paths – Mapping Devices [root@rhel6 ~]# for i in sdb sdc sdd sde; do printf “%s %s\n” “$i” ; “$(scsi_id –page=0x83 –whitelisted –device=/dev/$i)”;
linux udev
udev Rules – udev supplies the system software with device events, manages permissions of device nodes and may create additional symlinks in the /dev directory, or renames network interfaces. • udev rules are executed in numeric order –10-* rules are…
Seeing Linux Hardware
lsdev lsdev, lsusb, lspci cat /proc/devices cat /proc/scsci/scsi ls -lah /proc/kcore cat /proc/kcore ‘cat /proc/interrupts’ for which device is using which interrupt, also try ‘fdisk -l /dev/?d?’ for hard drive info, the ls /dev’