System File Checks Flashcards
lsblk -f
blkid
To get labels and UUIDs
Use -f
Non GPT
Shows device name, label name, UUID etc. great when you need more information than device name. Easier to read for device name too.
To add these to fstab file, we need to call those with GPT Label: PARTLABEL=[partition label]
blkid
For GPT
To add these to fstab file, we need to call those with GPT UUID: PARTUUID=[partition UUID label]
fstab
File in /etc/fstab
Can add drives to this to auto mount them on boot.
Shows drives, mount locations and file system types
can be safely viewed using the cat command
cat /etc/fstab
Most versions of Linux will use ext2, 3, 4.
3 & 4 are identical except, ext3 has journalling enabled. Ext4 is an improvement on that.
FS Auto - Rare to see, but it mounts it automatically. Only really okay for read only media like a CD-ROM drive. File checks can actually damage file systems when they are unknown.
plus dump and pass info for backing up and file checks on boot?
tunefs -L Sales /dev/vg1/Sales
Labeling
Dump
Dump column used to use the dump program to backup on reboot if 1 in the dump column.
Second to last column with long form
0= do not backup 1= perform backup
Pass
Pass column used to do a filesystem check during boot. Sets priority of scan
0 = don’t run filesystem check
1 = high priority filesystem check (get checked first)
2 = low priority filesystem check (get checked second so the system can continue to boot while these are checked)
UUID
Universally unique identifier
Aka GUID - Globally unique identifier
Used to identify partitions and as identity information in computer systems.
Drive options
auto/noauto
Options
auto/noauto - Automatically mount at boot time
user/nouser
- Allow non-root users to mount
exec/noexec - Allow executables
1
ro - Mount read-only
1
rw - Mount read-write
1
sync/async - Perform disk I/O
1
synchronous or asynchronous
Sync - Commands wait for writes to complete
Async - Commands terminate prior to writes completing
1
dev/nodev - Allow block devices (/dev/*)
1
usrquota/grpquota - Enable user/group quotas
1
suid - Allow the use of SetUID/SetGID
1
defaults - rw,suid,dev,exec,auto,nouser,asyn
Default settings as default options for drives
df -h
du
df to look at the disk as a whole
-h Shows human readable data (GBs and MBs)
du to look at the folders inside that disk
fsck -A
fsck -t ext2 /dev/sda2
fsck
FileSystem ChecK - checks file system for errors
the front end for the various filesystem tools
-A checks all filesystems
-t ext2 specifies filesystem type
/dev/sda2 is the specified drive
other examples:
e2fsck checks ext2/ext3 filesystems
To scan root drive:
Requires changes to fstab file and a reboot is required.
OR
Run a USB live Linux OS and scan the primary drive with fsck
mkfs
Builds a linux filesystem
Formats ext2/ext3/ext4
Front end for format utilities
mke2fs similar but for ext
debugfs
Special filesystem that resides in RAM
Useful for troubleshooting tools
dumpe2fs
Prints out filesystem information
example:
dumpe2fs -h /dev/sda1
human readable
tune2fs
tune the performance of a filesystem
change # of mounts between filesystem integrity checks
example:
tune2fs -c 60 -i 6m /dev/sda1
(60 mounts, 6 months)
Change a volume’s name
tune2fs -L Storage /dev/sdb1 tune2fs -l /dev/sda1 | grep volume
Convert ext2 to ext3
Enables journaling tune2fs -j /dev/sdc1
How should you use fsck to check the root drive on a CentOS server you have physical access to?
Run a USB live Linux OS and scan the primary drive with fsck
fsck -y /dev/[sda where OS is installed]
