Linux LPI 117-101 # 8 Of 9

Usually to mount the filesystem we use the mount command but that is
only for the current session. To mount the filesystem at boot time automatically we
use /etc/fstab.
Pattern of /etc/fstab
Device mount point filesystem mount options dump fsck
Example
LABEL=/ / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
LABEL=/home /home ext3 defaults,usrquota,grpquota 1 2
none /proc proc defaults 0 0
LABEL=/usr /usr ext3 defaults 1 2
LABEL=/var1 /var ext3 defaults 1 2
LABEL=SWAP-hda7 swap swap defaults

umask command is used to display and set the default permissions.
Here in #######*******QUESTION asking for the umask value of newly created file having

permission
644. If any permission is not changed then special permission i.e SUID, SGID and
sticky bits are not set.
Then in for have total permission for file is:
7666
-7644
0022

mount command displays all mounted filesystem and mount -a mount
all filesystem written /etc/fstab.

dd command creates the disk image, the above command creates the
image of boot.img and writes the image into /dev/fd0.

/home is the user's base directory where users home directory will
create. According to QUESTION that there are more than 100 users so /home needs to
mount on separate partition.

chown command change user and group ownership on file or
directory. Similalrly you can change the group ownership using the chgrp
command.
#chown userowner.groupowner file
#chown -R userowner.groupowner directory : This method is called recursively, it
changes the ownership of directory as well as all the conetents of directory.
#chgrp groupowner filename/directory

In terms of umask, you need to look at things backwards... When you

see a umask of 027 it's the same as a pattern of ----x-xxx, right? Now, since it's a
umask you need to INVERT that to figure out how it turns into an actual
permission string. That makes it xxxx-x---.

grpquota enables the group quota accounting and limits according to
the policy of administrator.
Example:
LABEL=/home /home ext3 defaults,grpquota 1 1

chown command is used to change the user owner and group owner of
file or directory.
Syntax: chown user:group file/directory
OR
chown user.group file/directory

chown [-hHLPR] [[user]] [:group] target1 [[target2 ..]]

dd command , which creates the disk image, the above command
cratest the image of /dev/hda1 and transfer into /dev/hdb1.
Similarly dd if=diskboot.img of=/dev/sda1 : Which creates the image of diskboot.img
and writes into /dev/sda1.

/var/spool/mail is the user's mail spooling directory and /var/www is
the directory used by the http service. So /var/ shoul in different partitions.

repquota command displays the quota report of particular filesystem.
#repquota /home : Which reports the information of quota on /home

If you haven't mounted the /var in different partition, it uses the space
from / parititions and /var has the world writable permission means others also can
write the files in /var/ so whenever others creates files it occupied space from /.

aquota.user is the quota information file as well as aquota.group is the
group quota information file, which files required to create in root filesystem.

umask is the command which display as well as set the default
permission.
First examine the given permission:
rw- for owner user : 6
r-- : for owner group member :4
r-- : for others: 4
It means total permission is 644
Now to set 644 default permission into file needs to subtract from 666
666
644
022
#umask 022

mount command lists all mounted file system. -a option is used to
mount all file system written in /etc/fstab.

According to the technical information available at Linux From
Scratch Ver 3.0, Before we start creating directories, we need to check the base
system's umask setting. To do this, we run umask. The result should be 022. If it
isn't, then run the following command to ensure that the directories will be created
with the correct permissions:
umask 022

There are two different default umask value one for root user and
another is for non-root user.
022 umask is for root user and 002 for the non-root user. It is defined globally in
/etc/bashrc file.

Answer C is correct. user options is used to allow an ordinary user to
mount the file system. The name of the mounting user is written to mtab so that
user can unmount the file system again.

Files umask value is 6 because normal file created using the text editor
do not have execute permission.
Maximum Permission to file 666
Applied Permission to file 666
Unmask value is -----
000

To execute the shell scripts required permission is read and execute.
#chmod a+x test.sh : Which sets the execute permission on test.sh file.

repquota prints a summary of the disk usage and quota for the
specified filesystem. For each user the current number of files and amount of space
is printed along with any quotas created with edquota.
Example: repquota /home : whch prints the quota information on /home.

Like files or directories, process also runs under the some ownership.
By default process start under the ownership of executer. Means who is going to
execute the command, process start under the ownership or security context of that
user or group. When SUID or SGID bit is set the executable file, process starts
under the security context of file owner then executer.
#chmod u+s file : which sets SUID bit on file
#chmod u+g file : Which sets SGID bit on file.

umask is the command which display as well as set the default
permission.
When set the umask 022 then permission on files :
666
022
644
It means rw-r--r-- permission will set on files and
777
022
755
rwxr-xr-x permission will set on directory.

The new permission is 654 to set this permission umask should set:
666
654
012
#umask 012
When set the umask 012 the permission will be 654 on file.

repquota prints a summary of the disk usage and quotas for the
specified file systems. For each user the current number of files and amount of
space (in kilobytes) is printed, along with any quotas created with edquota.
Example : repquota /home à prints the summary of disk usage and other information of
all users.

Steps of configure the quota
7. mount the partition using usrquota , grpquota option eg
LABEL=/home /home ext3 defaults,usrquota,grpquota 1 1 in fstab then reboot or
remount the filesystem
#mount -o remount /home
8. Create the quota Information file
#touch /home/aquota.user
#touch /home/aquota.group
9. Initialize the quota database
#quotacheck -ug /home
10. Enable the quota
#quotaon -ug /home
11. Apply the quota policy
#edquota -u user1 /home
12. Monitor the quota
#quota username
#repquota /home
aquota.user is the quota information file as well as aquota.group is the group quota
information file.

chown [-hHLPR] [[user]] [:group] target1 [[target2 ..]]

We can apply the quota policy on per paritions basis. If different
quota policy is required then needs to create the different partitions.

All filesystems written in /etc/fstab mount automatically at boot

time.
Syntax of /etc/fstab:
Device mountpoint filesystem mounting options dump frequency fsck order
LABEL=/ / ext3 defaults,acl 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
LABEL=/home /home ext3 defaults 1 2
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
LABEL=/usr /usr ext3 defaults 1 2
LABEL=/var /var ext3 defaults 1 2
LABEL=SWAP-hda13 swap swap defaults 0 0
/dev/hda14 /test ext3 defaults,acl 0 1
/dev/hda15 swap swap defaults 0 0
/dev/hdd /media/cdrom auto pamconsole,exec,noauto,managed 0 0
/dev/hdc /media/cdrecorder auto pamconsole,exec,noauto,managed 0 0

All filesystems written in /etc/fstab mount automatically at boot time.
Syntax of /etc/fstab:
Device mountpoint filesystem mounting options dump frequency fsck order
LABEL=/ / ext3 defaults,acl 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
LABEL=/home /home ext3 defaults 1 2
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
LABEL=/usr /usr ext3 defaults 1 2
LABEL=/var /var ext3 defaults 1 2
LABEL=SWAP-hda13 swap swap defaults 0 0
/dev/hda14 /test ext3 defaults,acl 0 1
/dev/hda15 swap swap defaults 0 0
/dev/hdd /media/cdrom auto pamconsole,exec,noauto,managed 0 0
/dev/hdc /media/cdrecorder auto pamconsole,exec,noauto,managed 0 0
to mount the nfs shared
Server:shared directory path mountpoint filesystem mounting point dump frequency fsck
order.

The symlink itself is only a pointer to the original file. If that file is deleted the pointer will point at an empty space.

chown [-hHLPR] [[user]] [:group] target1 [[target2 ..]]

To implement quota in partitions, we should mount with usrquota for
user quota, grpquota for group quota.
Example of mounting /home using usrquota and grpquota options.
LABEL=/home /home ext3 defaults,usrquota,grpquota 1 2

All filesystems written in /etc/fstab mount automatically at boot time.
Syntax of /etc/fstab:
Device mountpoint filesystem mounting options dump frequency fsck order
LABEL=/ / ext3 defaults,acl 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
LABEL=/home /home ext3 defaults 1 2
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
LABEL=/usr /usr ext3 defaults 1 2
LABEL=/var /var ext3 defaults 1 2
LABEL=SWAP-hda13 swap swap defaults 0 0
/dev/hda14 /test ext3 defaults,acl 0 1

/dev/hda15 swap swap defaults 0 0
/dev/hdd /media/cdrom auto pamconsole,exec,noauto,managed 0 0
/dev/hdc /media/cdrecorder auto pamconsole,exec,noauto,managed 0 0
user : allow a user to mount
Owner : allow device owner to mount
Pamconsole : allow a user at the console to mount

lsattr - list file attributes on a Linux second extended file system

rwx for everyone is a bit overkill, execute only will not be enough as
you can't access the file in that case. Read only for user will prohibit you from
executing it. So in the end you need both Read and Execute permission in the same
permission set.

The new permission is 600, to set this permission umask should set:
777
-600
177
# umask 177
When umask set 177 the permission on directory will be 600.

Usrquota enables the user quota accounting and limits according to the policy of
administrator.
Example:
LABEL=/home /home ext3 defaults,usrquota 1 1

quotaon announces to the system that disk quotas should be enabled
on one or more filesystems. The filesystem quota files must be present in the root
directory of the specified filesystem and be named either aquota.user (for version 2
user quota), quota.user (for version 1 user quota), aquota.group (for version 2
group quota), or quota.group (for version 1 group quota).

-R Recursively change file user and group IDs. For each file operand that names a
directory, chown shall change the user ID (and group ID, if specified) of the directory
and all files in the file hierarchy below it. Unless a -H, -L, or -P option is specified, it is
unspecified which of these options will be used as the default.

Default permission of /etc/passwd file in redhat enterprise linux is 644.
-rw-r--r-1 root root 3530 Aug 29 12:43 /etc/passwd

The given correct answer is "-rw-rw-r--". In UNIX/Linux systems, file permissions are represented by a 10-character string. The first character represents the file type, in this case, a regular file denoted by "-". The next three characters "rw-" indicate that the owner of the file has read and write permissions. The following three characters "rw-" indicate that the group members have read and write permissions. The last three characters "r--" indicate that others have only read permission. Therefore, if the unmask is set to 002, the new file will have permissions -rw-rw-r--.

chmod 755 ecuals xxx x-x x-x meaning rwx, rx, rx.

Here is the line of /etc/fstab
/dev/fd0 /media/floppy auto pamconsole,exec,noauto,managed 0 0
auto filesystem is used for removable media so it can't use in mounting option. So
Answer B is correct.

umask command is used to set the default permission to new file or
directory. It will not change the permission of already created files/directories.
To change the Permission of already created files/directories, should chmod command.

/mnt/cdrom or /media/cdrom is the mount point for cdrom specified in /etc/fstab.
/dev/hdd /media/cdrom auto pamconsole,exec,noauto,managed 0 0
/dev/hdc /media/cdrecorder auto pamconsole,exec,noauto,managed 0 0
So we need to mount just typing mount /media/cdrom command.

The default permission of /etc/shadow file in Redhat Enterprise Linux
is 400 means only the root user can read the file.
-r--------1 root root 3530 Aug 29 12:43 /etc/passwd

We can change the permission of file or directory using the chmod
command either using sumbolic method or numeric method.
Permission categories
u : Owner user
g : Owner Group
o : others
a : all
Permission types:
r : Read only : Numeric Value 4
w : Write : Numeric Value 2
x : Execute : Numeric Value 1
#chmod g+rwx filename : Which sets the read, write and execute permission to owner
group member on file.
#chmod 777 filename : Which sets the read, write and execute permission to all
-R option is called recursive, when you use this option in directory it changes the
permission to all the contents of directory.