Joseph Herlant
version 1.0.0, 2014-07-06 : Initial version

1. Basic filesystems operations

fdisk -l and parted -l are equivalent but RedHat recommends using parted over fdisk.

To force the kernel to reread the partition table, use the partprobe command.

To convert a filesystem from ext2 to ext3, use

umount /dev/sdb1
tune2fs -j /dev/sdb1

To create a swap partition on /dev/sdc1

mkswap /dev/sdc1
swapon /dev/sdc1
# Last, verify
swapon -s

Label a filesystem using:

e2label /dev/sdb1 my_label
# Then display the label to verify:
e2label /dev/sdb1
# And find the FS from the label
findfs LABEL=my_label

Get usefull infos about disks with the blkid command. Example:

# blkid
/dev/sda1: UUID="635f2b90-bb93-4221-88e2-5194a004aa52" TYPE="ext4"
/dev/sda2: UUID="4DmlAr-kOMB-0s17-GSxv-t0Sl-3fF2-Vqo6Of" TYPE="LVM2_member"
/dev/sdc1: UUID="187b93af-44c4-a179-06ae-2b7759e32205" UUID_SUB="71fee50b-4b50-4ce7-7a97-901b9a76e079" LABEL="RHEL01:0" TYPE="linux_raid_member"
/dev/sdb1: UUID="187b93af-44c4-a179-06ae-2b7759e32205" UUID_SUB="f164f4f6-d529-3d8e-93ef-ee6d5ae1870b" LABEL="RHEL01:0" TYPE="linux_raid_member"
/dev/sdd1: UUID="187b93af-44c4-a179-06ae-2b7759e32205" UUID_SUB="bbf9f4a1-1cca-5b1a-df4f-9eabe1e72a32" LABEL="RHEL01:0" TYPE="linux_raid_member"
/dev/mapper/VolGroup-lv_root: UUID="50eb8ea8-3c11-46c3-80c5-68a57075170a" TYPE="ext4"
/dev/mapper/VolGroup-lv_swap: UUID="c9ca22fc-fe01-4ee9-8607-66892a4aa794" TYPE="swap"

2. About XFS filesystems

XFS is now the default file system for RHEL7.

In RHEL 6.5, the /boot CANNOT be other than ext* file systems. Grub does not support vFAT, Btrfs, XFS or even LVM, so you can’t use thoses for /boot.

To create an XFS file system, you need to install the xfsprogs anc xfsdump packages (yum install -y xfsdump xfsprogs). Then the process would look quite familiar:

# We don't use LVM here, but you can! So let's create a new /dev/sdd1
# You can choose type 83, mkfs.xfs will do the rest
fdisk /dev/sdd
mkfs.xfs /dev/sdd1
mkdir /media/test_xfs
mount /dev/sdd1 /media/test_xfs
# Then update fstab
echo -e "$(blkid /dev/sdd1 | cut -d" " -f2) \t /media/test_xfs \t xfs \t defaults \t 1 \t 1" >> /etc/fstab

3. Permissions

The setuid flag (chmod u+s file or chmod 4755 file) is used to allow multiuser access, meaning that when running the file, the process running the file will be the owner of the file, not the user that launched it.

The setgid flag (chmod g+s folder or chmod 2770 folder) is used to allow multigroup access, meaning that the owner of the folder won’t be able to access the directory if not in the group that owns the file and that all files created in this folder will all be accessible in read/write to any member of the folder’s group owner.

The sticky bit flag (chmod o+t file or chmod 1775 file) prevents accidental delete by users or groups even if they have read/write access. Only root or the owner of the file (or directory) can delete it.