linux disks

Note: Do not place /usr on a separate partition

Mount a disk as read only / read write

mount -o remount,rw /path/to/mount
mount -o remount,ro /path/to/mount

Find a new disk

This is useful if you’ve hot-added another disk, such as with VMWare

echo "- - -" > /sys/class/scsi_host/host0/scan
echo "- - -" > /sys/class/scsi_host/host1/scan

LVM (Logical Volume Manager)

To Create LVM

fdisk /dev/sda ->create 3 partitions + label to 8e
partprobe
fdisvk -l
pvcreate /dev/sda8 /dev/sda9
pvdisplay /dev/sda8
pvdisplay /dev/sda9
vgcreate vg0 /dev/sda8 /dev/sda9
vgdisplay
lvcreate -L +15g -n label_home /dev/vg00
lvcreate -l +100%FREE -n lv_name /dev/vg01
lvdisplay /dev/vg0/home1
lvcreate -L +300M -n /dev/vg0/var1
lvcreate -L +200GB -n oracle-export vg01
lvdisplay /dev/vg0/var1
mkfs.ext3 /dev/vg0/var1
mkfs.ext3 /dev/vg0/home1
mkdir /home1
mkdir /var1
mount /dev/vg0/home1 /home1
mount /dev/vg0/var1 /var1
cp /etc/a* /home1
cp /etc/b* /var1
vim /etc/fstab
mount -a

LVM SNAPSHOT

lvcreate -L 200M -s -n lv2 /dev/llc/lv1

To find the mapping of an LV

lvdisplay -m

Extend PV

pvcreate /dev/sda999
pvdisplay

To extend VG

vgextend vg00 /dev/sda999
vgdisplay vg00

To reduce VG

vgreduce vg00 /dev/sda999
vgdisplay

TO EXTEND LV (Adding 200M)

lvdisplay /dev/vg00/home
lvextend -L +200M /dev/vg00/home
lvextend -L +200M /dev/vg00/home /dev/sdc1
lvextend -l +100%FREE /dev/myvg/testlv
(optional) umount /home
resize2fs /dev/vg0/home
(optional) mount /home

To reduce LVM (Reducing to 100M)

lvdisplay
umount /var1
e2fsck -f /dev/vg0/var1
resize2fs /dev/vg0/var1 100M
lvreduce -L 100M /dev/vg0/var1
mount /dev/vg0/var1 /var1
df -h

TO REDUCE PV

pvremove /dev/sda10 pvdisplay

REMOVE LVM

lvdisplay umount /dev/vg0/home1 umount /dev/vg0/var1 vi /etc/fstab lvremove /dev/vg0/home1 lvremove /dev/vg0/var1 lvdisplay

REMOVE VG

vgdisplay vgremove /dev/vg0 vgdisplay

REMOVE PV

pvdisplay pvremove /dev/sda9 pvremove /dev/sda8

Label a filesystem

e2label /dev/sdb2 usbstroage

You can add to /etc/fstab “LABEL=labelname”

# <file system>           <mount point>    <type>  <options>            <dump>  <pass>
proc                      /proc            proc    nodev,noexec,nosuid  0       0
/dev/mapper/server-root   /                ext4    errors=remount-ro    0       1
UUID=nnnnnnnnnnnnnnnnnn  /boot  ext2  defaults        0       2
/dev/mapper/server-swap_1 none             swap    sw                   0       0
LABEL=seagate             /mnt/seagate     ntfs    defaults             0       2
LABEL=backup              /mnt/backup      ext4    ro,nosuid,noexec     0       2
LABEL=wd3tbgreen          /usr/local/var/crashplan/  ext4    nosuid,noexec        0       2

Adding swap

swapon -s
lvcreate -L +16G -n /dev/vg00/swap2
mkswap /dev/mapper/vg00-swap2
vi /etc/fstab
swapon -a
swapon -s

Which disk is an LV on

pvdisplay -m
lvdisplay -m
lvs -o +devices
lvs -a -o +devicesq

From Shane

Linux rescue + lvm

Reboot. Edit grub config On the end of the kernel line put “init=/bin/bash” This mounts root as read only mount -o remount,rw / Make whatever changes are required (you might need to mount /proc) Unmount anything mounted mount -o remount,ro / Afterwards “reboot” (not CTRL-D or it will lock up!!!)

To do a linux rescue boot (for resetting the root password for example) :

Mount a redhat iso/dvd and boot off it
Type “linux rescue” at the prompt
Tell the OS not to mount the disks or connect the network interfaces
When it boots type
lvm vgscan
lvm vgchange -a y
The vg should be under /dev/[vg]/[lv] - which will likely link to /dev/mapper (eg /dev/mapper/vg00-root)
Use this device to mount / fsck this volume as necessary
Other commands - “lvm lvscan” and “dmsetup status”

Running ‘fdisk -l’ should give you an overview of attached storage, partitions and file system types. Running ‘pvscan’ should show the Physical Volums (PV). Running ‘vgscan’ the Volume Groups (VG). Running ‘vgchange -ay’ should then enable your LVM. Running ‘lvscan; dmsetup status’ afterwards should show the Logical Volumes (LV) and what directory they’re attached to in /dev/ for mounting purposes. Now with ‘mount /dev/VOLUMEGROUPNAME/LOGICALVOLUMENAME /some/directory’ you can mount the LV, e.g.: ‘mount /dev/vg0001/lv001 /mnt/temp/ -o ro’ should mount LV name “lv001” inside the “vg0001” VG at mountpoint /mnt/temp read-only (as you wouldn’t want to change things while making backups).