Tag Archives: ext4

LVM: reduce partition size

# umount mountpoint with lvm partition
unmount /data

# check for errors and fix them
fsck -f /dev/sys/data

# resize filesystem to 80Gb
resize2fs /dev/sys/data 80G

# deactivate logical volume
lvchange -an /dev/sys/data

# change size of logical volume
lvreduce --size 191G /dev/sys/data

# create new volume «drbdmaster» in logical group «sys» with size 4Gb
lvcreate -n drbdmaster -L4G sys

# activate volumes
lvchange -ay  /dev/sys/data
lvchange -ay /dev/sys/drbdmaster

# mount data
mount /dev/sys/data

# create filesystem on drbdmaster
mkfs.ext4 /dev/sys/drbdmaster

# mount drbdmaster
mkdir -p /drbd/master
mount /dev/sys/drbdmaster /drbd/master

e2fsck cheatsheet

e2fsck has softlinks in /sbin that one can use to keep the names of fsck tools more uniform. i.e. fsck.ext2, fsck.ext3 and fsck.ext4 (similarly, other filesystem types have e.g.: fsck.ntfs) This cheatsheet will make use of these softlinks and will use ext4 and /dev/sda1 as an example.

fsck.ext4 -p /dev/sda1 — will check filesystem on /dev/sda1 partition. It will also automatically fix all problems that can be fixed without human intervention. It will do nothing, if the partition is deemed clean (no dirty bit set).

fsck.ext4 -p -f /dev/sda1 — same as before, but fsck will ignore the fact that the filesystem is clean and check+fix it nevertheless.

fsck.ext4 -p -f -C0 /dev/sda1 — same as before, but with a progress bar.

fsck.ext4 -f -y /dev/sda1 — whereas previously fsck would ask for user input before fixing any nontrivial problems, -y means that it will simply assume you want to answer «YES» to all its suggestions, thus making the check completely non-interactive. This is potentially dangerous but sometimes unavoidable; especially when one has to go through thousands of errors. It is recommended that (if you can) you back up your partition before you have to run this kind of check. (see dd command for backing up filesystems/partitions/volumes)

fsck.ext4 -f -c -C0 /dev/sda1 — will attempt to find bad blocks on the device and make those blocks unusable by new files and directories.

fsck.ext4 -f -cc -C0 /dev/sda1 — a more thorough version of the bad blocks check.

fsck.ext4 -n -f -C0 /dev/sda1 — the -n option allows you to run fsck against a mounted filesystem in a read-only mode. This is almost completely pointless and will often result in false alarms. Do not use.

ext2 -> ext4 on SSD

umount /ssd # (if you have root «/» partition on ssd you should use livecd).
tune2fs -O extents,uninit_bg,dir_index,has_journal /dev/sdXN
# where /dev/sdXN is partition on the ssd
e2fsck -pf /dev/sda1 # you have to make check disk after converting fs
edit /etc/fstab
# discard options instead of default for enabling TRIM !
/dev/sdXN /ssd ext4 discard 1 2

mount -a