File System Consistency Check Tool
You can manually check the file system by using the file system consistency check tool,
fsck, after you unmount the file system.
The Photon OS file system includes btrfs and ext4. The default root file system is ext4, which you can see by looking at the file system configuration file,
``` cat /etc/fstab #system mnt-pt type options dump fsck /dev/sda1 / ext4 defaults,barrier,noatime,noacl,data=ordered 1 1 /dev/cdrom /mnt/cdrom iso9660 ro,noauto 0 0 ```
1 in the fifth column, under
fsck, indicates that fsck checks the file system when the system boots.
You can also perform a read-only check without unmounting it:
``` fsck -nf /dev/sda1 fsck from util-linux 2.27.1 e2fsck 1.42.13 (17-May-2015) Warning! /dev/sda1 is mounted. Warning: skipping journal recovery because doing a read-only filesystem check. Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information Free blocks count wrong (1439651, counted=1423942). Fix? no Free inodes count wrong (428404, counted=428397). Fix? no /dev/sda1: 95884/524288 files (0.3% non-contiguous), 656477/2096128 blocks ```
The inodes count might be wrong because the file system is mounted and in use.
To fix errors, you must first unmount the file system and then run fsck again:
``` umount /dev/sda1 umount: /: target is busy ```
You can find information about processes that use the device by using
``` lsof | grep ^jbd2/sd jbd2/sda1 99 root cwd DIR 8,1 4096 2 / jbd2/sda1 99 root rtd DIR 8,1 4096 2 / jbd2/sda1 99 root txt unknown /proc/99/exe ```
The above example indicates that file system is in use.