Linux Administration

There must be an entry in /sys/block/XXX # ls -lrt /sys/block/ /proc/partitions ==> cat /proc/partitions  major minor  #blocks  name    8        0   15728640 sda    8        1     512000 sda1    8        2   15215616 sda2    8       16    2097152 sdb  253        0   13148160 dm-0  253        1    2064384 dm-1 To list all the disk in the machine ==> fdisk -l # fdisk -l /dev/?d? To avoid all the dm devices. # fdisk -l 2>/dev/null | grep "Disk \/" Disk /dev/sda: 16.1 GB, 16106127360 bytes Disk /dev/sdb: 2147 MB, 2147483648 bytes Disk /dev/mapper/VolGroup-lv_root: 13.5 GB, 13463715840 bytes Disk /dev/mapper/VolGroup-lv_swap: 2113 MB, 2113929216 bytes # lsblk NAME                   ...

Assuming that you have already created a physical volume ==> volume group. If not then click here..... Now firstly create a logical volume. Check the free space in your volume group by firing a command in terminal as vgdisplay VOLUMEGROUP NAME. [root@sunny ~]# vgdisplay vg_sunny   --- Volume group ---   VG Name               vg_sunny   System ID                Format                lvm2   Metadata Areas        1   Metadata Sequence No  3   VG Access             read/write   VG Status             resizable   MAX LV                0   Cur LV                2   Open LV               2   Max PV ...

Creating and activating a SWAP partition Check for any free space that is available in your HDD. [root@sunny ~]# parted GNU Parted 2.1 Using /dev/vda Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) print free                                                       Model: Virtio Block Device (virtblk) Disk /dev/vda: 21.5GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number  Start   End     Size    Type      File system     Flags         32.3kB  1049kB  1016kB            Free Space  1      1049kB  525MB   524MB   primary   ext4            boot  2      525MB   4720MB  4194MB  prima...

In Linux the file system is based on one root directory, or hierarchical top point with subdirectories below it. In which each sub-directories has its own importance like some act as mount points, some for log messages, some for all hardware devices etc. You can find a brief description of all the directories and sub directories below: / : Its the top most directory in any of the Unix based system. /bin : Essential command binaries that need to be available in single user mode; for all users, e.g. , cat, ls, cp. / boot : Boot loader files, e.g. , kernels, initrd etc. /dev : Information of all the hardware devices. /etc : All the config files. /home : Home directories of all the users in a particular machine. /media : Mount points for removable media such as USB, CD etc. /mnt : For temporary mount points. /opt : Optional software packages like openoffice etc. /root : Home directory of root user. /sbin : System binaries like init, ip etc. /tmp : Temporary files. Ofte...

Single user mode is a mode in which a multiuser computer operating system boots into a single superuser. It is mainly used for maintenance of multi-user environments, Basically single user mode in unix based systems is known as runlevel 1. Some tasks may require exclusive access to shared resources, for example running fsck on a network share or to retrieve a lost superuser password or any maintenance task. For gaining access to #(root) prompt what you need to do is ? Once your machine is booting, for getting access to # prompt your just need to edit the bootloader i.e. in case of RHEL6 its GRUB (GRand Unified Bootloader).  Once your machine is booting just press a key couple of time so that you are brought to the GRUB menu. The GRUB menu appears like the image shown below: The values which are show in this window are the kernerl(s) which are installed in your machine. Use the cursor keys to switch between kernels (if you have mo...