Linux Cheat Sheet

Table of Contents

Single User Boot

To perform single user boot with GRUB perform the steps:

type p and password if required
type e to enter edit mode
select the kernel command line and append single for single user boot, or run level number (1 through 5)
type b to boot the system

UTF-8

Both vi (vim) and emacs will grok UTF-8 if you set LANG appropriately, e.g.:

export LANG=en_US.UTF-8

Logical and Physical Volume Groups

Adding a new disk and putting it in its own logical volume

Preparation

First, add the hardware.

Then, use the GUI Disk Utility to format the disk (i.e., to create the partition table). Do NOT create a file system.

Create the physical volume

Use fdisk -l to verify which device is associated with the new disk. Then, at the command line. create a physical volume. Let’s suppose the disk is /dev/sdb:

# pvcreate /dev/sdb

Doesn’t hurt to verify the creation with pvdisplay.

Create the volume group

Next, create the volume group. With a single partition:

# vgcreate drive2 /dev/sdb

drive2 is an arbitrary name for the volume group. It can be anything, as long as it doesn’t clash with an existing volume group’s name.

To group multiple partitions in the same group:

# vgcreate drive2 /dev/sdb /dev/sdc ...

Now, run vgdisplay to show the new volume group configuration.

Create the logical volumes

# lvcreate --name usrlocal --size 80G drive2
# lvcreate --name home2 --size 160G drive2

To use 100% of all disks:

# lvcreate --name foo --extents 100%FREE drive3

Format and mount the new volumes:

# mkfs.ext4 /dev/drive2/usrlocal
# mkfs.ext4 /dev/drive2/home2
# mount /dev/drive2/usrlocal /usr/local
# mount /dev/drive2/home2 /home2

Reference: http://www.davelachapelle.ca/guides/ubuntu-lvm-guide/

Adding a new disk to an existing volume group.

Create the physical volume, as described above. Then:

Unmount the existing logical volume

# umount /dev/volgroup1/logicalvol0

Add the new physical volume to the parent volume group

# vgextend volgroup1 /dev/sdb1

Add space to the logical volume

Decide how much of the new physical volume should go an existing volume group, if any. If any percentage of the drive is being used to extend an existing logical volume, extend the logical volume. In this example, the entire new volume group is being added. (See lvextend(8) for more info.)

# lvextend /dev/volgroup1/logicalvol0 /dev/sdk1

Resize the logical volume

# e2fsck -f /dev/volgroup1/logicalvol0

If that fails to get all the space, then recreate the file system from scratch:

# mkfs.ext4 /dev/volgroup1/logicalvol0