C2110 UNIX and programming Lesson 4 / Module 2 -1C2110
UNIX and programming
Petr Kulhanek
kulhanek@chemi.muni.cz
National Center for Biomolecular Research, Faculty of Science
Masaryk University, Kamenice 5, CZ-62500 Brno
PS / 2020 Distance form of teaching: Rev1
Lesson 4 / Module 2
C2110 UNIX and programming Lesson 4 / Module 2 -2File
System
C2110 UNIX and programming Lesson 4 / Module 2 -3-
Quotas
Quotas are set for your home directories on disk partition wolf.ncbr.muni.cz:/home/. The
current status and quota settings can be seen by the command quota:
[kulhanek@wolf ~]$ quota -vs
Disk quotas for user kulhanek (uid 18773):
Filesystem blocks quota limit grace files quota limit
wolf.ncbr.muni.cz:/home/
1550M 1954M 2051M 20453 0 0
Current use
Quota that can be temporarily exceeded.
Hard limit that cannot be exceeded.
Exceeded quota can lead to unsuccessful login using a graphical interface. In this case, log
into a text terminal (e.g., Ctrl + Alt + F1) and move the files to another partition (e.g.,
temporarily to the /scratch/username or delete unnecessary files).
C2110 UNIX and programming Lesson 4 / Module 2 -4Disk
Device
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/server1-root ext4 15G 8.4G 5.5G 61% /
none tmpfs 4.0K 0 4.0K 0% /sys/fs/cgroup
udev devtmpfs 3.9G 4.0K 3.9G 1% /dev
tmpfs tmpfs 793M 888K 792M 1% /run
none tmpfs 5.0M 0 5.0M 0% /run/lock
none tmpfs 3.9G 952K 3.9G 1% /run/shm
none tmpfs 100M 36K 100M 1% /run/user
/dev/mapper/server1-vbox ext4 64G 52G 9.5G 85% /win
/dev/mapper/server1-scratch ext4 598G 2.8G 565G 1% /scratch
wolf.wolf.inet:/software/ncbr nfs4 197G 156G 33G 83% /software/ncbr
wolf.wolf.inet:/home/ nfs4 493G 371G 98G 80% /home
device file system type mount point
An overview of file system usage, disk devices, and their mount points is provided by the
command df.
Ext3, ext4 third / fourth extended filesystem (native file system of linux)
nfs3, nfs4 network filesystem
Vfat Virtual File Allocation Table (file system used by MS Windows)
ntfs New technology File System (developed by Microsoft for its operating systems)
File system types:
!!! not case-sensitive !!! - Be careful when copying files with different cases
C2110 UNIX and programming Lesson 4 / Module 2 -5USB
Drives
[kulhanek@wolf01 ~]$ df -Th
Filesystem Type Size Used Avail Use% Mounted on
................................................................................
wolf.ncbr.muni.cz:/home nfs4 280G 164G 102G 62% /home
/dev/sdg1 vfat 962M 841M 122M 88% /media/kulhanek/B19A-1CA2
In the graphic environment, USB drives connect automatically into the bundle
/media/username.
[kulhanek@wolf01 ~]$ umount /media/kulhanek/B19A-1CA2
The disk can be disconnect in a graphical environment or by a command umount. The
command argument is the device mount point.
The disk can be disconnected only if it is not in use (no file must be open, no process must
have a (sub)directory from the mount point, including the mount point, set as the working
directory). An overview of the processes using the given directory (mount point) can be
obtained by the command lsof (or fuser).
[kulhanek@wolf01 ~]$ lsof /media/kulhanek/B19A-1CA2/
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
bash 31521 kulhanek cwd DIR 8,97 4096 518 /media/kulhanek/B19A-1CA2/GoslarFinal
bash 31893 kulhanek cwd DIR 8,97 4096 518 /media/ kulhanek/ B19A-1CA2/GoslarFinal
vi 32011 kulhanek cwd DIR 8,97 4096 518 /media/ kulhanek/ B19A-1CA2/GoslarFinal
C2110 UNIX and programming Lesson 4 / Module 2 -6-
Links
Links:
➢ Hard links
➢ Symbolic links (soft links)
Symbolic links (soft links)
lrwxrwxrwx 1 root root 21 Oct 5 21:06 krb5.conf -> /etc/krb5.conf.EINFRA
-rw-r - r-- 1 root root 4848 Oct 5 20:37 krb5.conf.EINFRA
symbolic link
real file
link target
Properties of symbolic links:
• contain information about the path to the target object (file, directory,…)
• from the point of view of the system, they behave as the target object
• access rights are derived from the target object
• the target object may not exist
• they are created with the command ln with the -s option, example:
ln –s /etc/krb5.conf.EINFRA krb5.conf
C2110 UNIX and programming Lesson 4 / Module 2 -7Overview
of Commands
File system:
cd changes the current working directory
pwd lists the path to the current working directory
ls lists the contents of a directory
Mkdir creates a directory
rmdir deletes a directory (must be empty)
Cp copies a file or directory
mv moves a file or directory
rm deletes a file or directory
find searches for files or directories
Id lists the user's groups
getent lists information about users, user groups, and other information
chmod changes access rights to a file or directory
chown changes the owner of the file or directory
chgrp changes the access group of a file or directory
umask default access rights for newly created files or directories
basic operations
access rights
C2110 UNIX and programming Lesson 4 / Module 2 -8Overview
of Commands
File system (continued):
quota prints information about set quotas for mount points
du lists the size of directories or files
stat lists detailed information about a file or directory
df lists information about mounted partitions
lsof lists processes that have files / directories open on a mount point
(directory)
ln creates a link to a file or directory
unlink unlinks a file or directory
advanced functions
C2110 UNIX and programming Lesson 4 / Module 2 -9Exercise
1
1. Use the command quota to view the current occupancy of your home
directory on a WOLF cluster.
2. Download this presentation to your home directory.
3. What is the size of the presentation file?
4. Create a symbolic link to the presentation named lesson4.pdf.
5. What is the size of the symbolic link?
6. Delete the presentation file.
7. Is there a symbolic link? If so, is the link valid?
8. Delete the symbolic link.