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Thursday, September 9, 2010

LINUX INTERVIEW QUESTIONS : FTP

LINUX INTERVIEW QUESTIONS : FTP


1)What is the difference between TFTP and FTP servers?A)Both are file transfer servers but slight difference is TFTP server uses UDP protocol and FTP uses TCP protocol. TFTP is good for slow connection paths.

2)What is the port no for FTP?
A)20 for Data and 21 for Control(normally when an interviewer ask's ftp port number just say 21.

3)What is the port no for TFTP?
A)69.

4) How to restrict users to their home directories?A)By setting up "chroot_local_user=YES".

5)How to restrict total number of users accessing FTP server?A1) If Vsftpd is running under xinted service, then you can use xineted to get per-service per IP connection limits or
A2) If you run vsftpd in "standalone" mode with the "setting listen=YES", then
you can investigate the setting (e.g.) : "max_clients=10"


6)I want to copy multiple files with out prompting for any info, how can I do that one?A)Simply do "ftp -i ftpserver" this command will suppress any info displayed on ftp server.
or you can just type prompt ftp prompt to suppress info messages have a look here.

7) Some times Local users cannot log in. How to resolve this issue?A) Check "local_enable=YES" in your /etc/vsftpd/vsftpd. conf to allow local users to log in.
8) How do we integrate with LDAP( Lightweight Directory Access Protocol )users and login?A) Use vsftpd's( Very Secure FTPD) PAM(Pluggable Authentication Modules) integration to do this, and have PAM authenticate against an LDAP repository.

9) Can we host different ftp sites on single machine, I mean virtual hosting concept like Apache?A1) Yes. If you integrate vsftpd with xinetd, you can use xinetd to bind to several different IP addresses. For each IP address, get xinetd to launch vsftpd with a different config file. This way, you can get different behavior per virtual address.
A2) Alternatively, run as many copies as vsftpd as necessary, in standalone
mode. Use "listen_address=x.x.x.x" to set the virtual IP.


10) How to restrict different users with different permissions in vsftpdA) By setting up "user_config_dir" entry in "vsftpd.conf".


11)How to change vsftpd default port?A)By setting "listen_port" option in "vsftpd.conf".
12) Vsftpd is reporting times as GMT times and not local times!. How to resolve this?A) This behavior can be changed with the setting "use_localtime=YES".


13) How to disable certain FTP commands?
A) There are some individual settings (e.g. dirlist_enable) or you can specify a complete set of allowed commands with "cmds_allowed".


14) How does vsftpd support per-IP limits?A1) If you are running vsftpd standalone, there is a "max_per_ip" setting.
A2) Yes. If you are running vsftpd via xinetd, there is an xinetd config variable "per_source".


15) How Does vsftpd can do bandwidth limiting?A) settings such as "anon_max_rate" and "local_max_rate" can be used to set this limits.

16) How to restrict some IP's not use my FTP server?A1) vsftpd can integrate with tcp_wrappers (if built with this support). It is enabled with the setting "tcp_wrappers=YES".
17) Does vsftpd support IPv6?A) Yes, as of "version 1.2.0".

18) Help! I'm getting messages along the lines of "500 OOPS: vsf_sysutil_bind" when trying to do downloads (particularly lots of small files).A) "vsftpd-1.2.1" should sort this out.

19) Can we use vsftpd to hiding or denying certain files?A) Yes. Look at the hide_file and deny_file options.

20)How you can check if there is any syntax error in vsftpd.conf file?A)Just type vsftpd with out quoats.