q08-disk-management
Énoncé§
Solve this question on: terminal
Your team selected you for this task because of your deep filesystem and disk/devices expertise. Solve the following steps to not let your team down:
-
Format
/dev/vdbwithext4, mount it to/mnt/backup-blackand create empty file/mnt/backup-black/completed. -
Find which of the two disks,
/dev/vdcor/dev/vdd, has higher storage usage. Then empty the.trashfolder on it. -
There are two processes running:
dark-matter-v1anddark-matter-v2. Find the one that consumes more memory or virtual memory.Then unmount the disk where the process executable is located on.
Solution§
A good way to start is probably to list existing disks:
sudo fdisk -l
Disk /dev/vdb: 100 MiB, 104857600 bytes, 204800 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/vdc: 100 MiB, 104857600 bytes, 204800 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/vdd: 100 MiB, 104857600 bytes, 204800 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/vde: 100 MiB, 104857600 bytes, 204800 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/vdf: 100 MiB, 104857600 bytes, 204800 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Another way with good list style and information:
lsblk -f
NAME FSTYPE FSVER LABEL ... FSAVAIL FSUSE% MOUNTPOINTS
...
vdb
vdc ext4 1.0 ... 0 98% /mnt/backup001
vdd ext4 1.0 ... 77.7M 6% /mnt/backup002
vde ext4 1.0 ... 82.6M 0% /mnt/app-8e127b55
vdf ext4 1.0 ... 82.6M 0% /mnt/app-4e9d7e1e
...Or even another way:
df -h
Filesystem Size Used Avail Use% Mounted on
tmpfs 198M 1.1M 197M 1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv 62G 5.6G 54G 10% /
tmpfs 988M 0 988M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
/dev/vda2 2.0G 130M 1.7G 8% /boot
tmpfs 198M 4.0K 198M 1% /run/user/1000
/dev/vdc 90M 51M 33M 61% /mnt/backup001
/dev/vdd 90M 5.1M 78M 7% /mnt/backup002
/dev/vde 90M 44K 83M 1% /mnt/app-8e127b55
/dev/vdf 90M 44K 83M 1% /mnt/app-4e9d7e1eStep 1§
We go right ahead and format the disk:
sudo mkfs -t ext4 /dev/vdb
mke2fs 1.46.5 (30-Dec-2021)Creating filesystem with 25600 4k blocks and 25600 inodes
Allocating group tables: done
Writing inode tables: done
Creating journal (1024 blocks): done
Writing superblocks and filesystem accounting information: done
Then we mount it at the required location and create the file:
sudo mkdir /mnt/backup-black
sudo mount /dev/vdb /mnt/backup-black
sudo touch /mnt/backup-black/completed
df -h
Filesystem Size Used Avail Use% Mounted on
tmpfs 198M 1.4M 197M 1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv 62G 7.5G 52G 13% /
tmpfs 988M 0 988M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
/dev/vda2 2.0G 130M 1.7G 8% /boot
tmpfs 198M 4.0K 198M 1% /run/user/1000
tmpfs 1.0M 0 1.0M 0% /var/snap/lxd/common/ns
/dev/vdc 90M 51M 33M 61% /mnt/backup001
/dev/vdd 90M 5.1M 78M 7% /mnt/backup002
/dev/vde 90M 44K 83M 1% /mnt/app-8e127b55
/dev/vdf 90M 44K 83M 1% /mnt/app-4e9d7e1e
/dev/vdb 90M 24K 83M 1% /mnt/backup-black # this is us
tmpfs 198M 4.0K 198M 1% /run/user/0Step 2§
Now we need to check the used disk space of two disks:
df -h
Filesystem Size Used Avail Use% Mounted on
tmpfs 198M 1.4M 197M 1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv 62G 7.5G 52G 13% /
tmpfs 988M 0 988M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
/dev/vda2 2.0G 130M 1.7G 8% /boot
tmpfs 198M 4.0K 198M 1% /run/user/1000
tmpfs 1.0M 0 1.0M 0% /var/snap/lxd/common/ns
/dev/vdc 90M 51M 33M 61% /mnt/backup001 # compare
/dev/vdd 90M 5.1M 78M 7% /mnt/backup002 # compare
/dev/vde 90M 44K 83M 1% /mnt/app-8e127b55
/dev/vdf 90M 44K 83M 1% /mnt/app-4e9d7e1e
/dev/vdb 90M 24K 83M 1% /mnt/backup-blackWe see that we need to clear up disk space on /mnt/backup001:
sudo rm -rf /mnt/backup001/.trash/*The results should be shown:
df -h
...
/dev/vdc 90M 28K 83M 1% /mnt/backup001 # much space gained
/dev/vdd 90M 5.1M 78M 7% /mnt/backup002Step 3§
For the final step we need to check the memory of two processes and then find out on which disk the largest consumer runs:
ps aux | head -n 1
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
ps aux | grep dark-matter
root 51658 0.0 0.1 7380 3584 ? S 14:57 0:00 /mnt/app-8e127b55/dark-matter-v1
root 51659 0.0 0.1 16596 3456 ? S 14:57 0:00 /mnt/app-4e9d7e1e/dark-matter-v2It would also be possible to use top -b | grep dark for example.
We see the MEM and VSZ usage and the full paths at the very end. This means process dark-matter-v2 is the offender and the executable is to be found at /mnt/app-4e9d7e1e/dark-matter-v2. So we need to do:
df -h | grep /mnt/app-4e9d7e1e
/dev/vdf 90M 44K 83M 1% /mnt/app-4e9d7e1e # to see the disk and mount point
sudo umount /mnt/app-4e9d7e1eumount: /mnt/app-4e9d7e1e: target is busy.
The disk is busy, probably because of that one process! But we can check for any other processes blocking this:
sudo lsof | grep /mnt/app-4e9d7e1e
dark-matt 6204 root txt REG 252,80 16488 12 /mnt/app-4e9d7e1e/dark-matter-v2Well, only that one bad process! Hence we can finish this question with:
sudo kill 6204 # your PID will be different
sudo umount /mnt/app-4e9d7e1e