Sys Admin

Question 1

What command would you use to check memory performance?

Answer 1

vmstat

vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.

The first report produced gives averages since the last reboot. Additional reports give information on a sampling period of length delay. The process and memory reports are instantaneous in either case.

Or use memstat

Question 2

What is the man command used for?

Answer 2

It displays information about the syntax for a command.

Question 3

What tools are used to measure disk I/O?

Answer 3

vmstat - Report virtual memory statistics.
memstat -
iostat - Report CPU statistics and i/o statistics for devices, partitions and network filesystems (NFS).
sar - Collect, report, or save system activity information.

Question 4

Where is the httpd.conf file located?

Answer 4

/etc/httpd/conf/httpd.conf

Question 5

How would you restart the https service?

Answer 5

/usr/sbin/apachectl restart

Question 6

If the httpd service having issues restarting, where would you look for more information?

Answer 6

/var/log/httpd/error_log

Question 7

What log would you look in to find issues that may have happened during the boot process?

Answer 7

/var/log/dmesg
/var/log/boot.log
/var/log/messages

Question 8

How can you find which ports are listening on a server, both locally and remotely?

Answer 8

Locally:
netstat –listen
netstat -tuplan
lsof -i (list open files)

Remotely:
nmap
netcat

Question 9

What is the chroot command?

Answer 9

chroot on Unix operating systems is an operation that changes the apparent root directory for the current running process and its children. A program that is run in such a modified environment cannot name (and therefore normally not access) files outside the designated directory tree.

Question 10

Where are default system / service config files located?

Answer 10

/etc/sysconfig/

Question 11

How would you restart the httpd service?

Answer 11

/usr/sbin/apachectl restart

service httpd restart

Question 12

What default port does HTTPS listen on?

Answer 12

443

Question 13

What would occur if the system were booted into run level 3 and the command “init 1” was executed from the command-line?

Answer 13

As root, that would put the system into single user mode without a reboot

Question 14

What is the difference between run level 3 and run level 5?

Answer 14

run level 3 is the default multiuser run level, run level 5 is for X11 or graphical/desktop.

Question 15

What is the significance of the init process?

Answer 15

init - short for initialisation is a daemon process that is the direct or indirect ancestor of all other processes.

Question 16

What commands are used to modify file permissions?

Answer 16

chmod - change file mode bits

chown - change file owner and group

Question 17

Assuming a shell script, script.sh, has executable permissions, how can you run that script?

Answer 17

If in path, then script.sh if not then /script.sh or if in current directory ./script.sh
If not executable then . ./script.sh

Question 18

What default port does FTP listen on?

Answer 18

21

Question 19

What default port does ssh listen on?

Answer 19

22

Question 20

What default port does MySQL listen on?

Answer 20

3306

Question 21

What default port does IMAP listen on?

Answer 21

143

Question 22

What default port does pop3 listen on?

Answer 22

110

Question 23

What default port does SMTP listen on?

Answer 23

25

Question 24

What default port does HTTP listen on?

Answer 24

80

Question 25

Can you run out of inodes while still having plenty of available disk space on the file system?

Answer 25

Trick question…

Some file system such as ext3 create all the inodes when the file system is created. Thus it is possible to run out of storage because all of the inodes are used yet the storage still has unused capacity. To help get around this other file systems such as ext4 and xfs, create inodes as needed.

Question 26

What is the purpose of the fstab file?

Answer 26

File system table The fstab (/etc/fstab) (or file systems table) file is a system configuration file commonly found on Unix systems. It is part of the util-linux package. The fstab file typically lists all available disks and disk partitions, and indicates how they are to be initialized or otherwise integrated into the overall system’s file system.

Question 27

What is an inode?

Answer 27

Each inode (index node) stores all the information about a file system object (file, directory, device node, socket, pipe, etc.), except data content and file name

Question 28

What would the command “mount –a” do?

Answer 28

(usually given in a bootscript) causes all file systems mentioned in fstab (of the proper type and/or having or not having the proper options) to be mounted as indicated, except for those whose line contains the noauto keyword.

Question 29

What log would you look in to find issues that may have happened during the boot process?

Answer 29

/var/log/dmesg
/var/log/boot.log
/var/log/messages

Question 30

What commands can be used to display one page of output at a time to the screen?

Answer 30

more or less

Question 31

What command can be used to decompress the file foo.gz?

Answer 31

gunzip foo.gz

Question 32

What default port does SNMP listen on?

Answer 32

161

162 for SNMP traps