Under Linux operating system you can use the faillog command to display faillog records or to set login failure limits. faillog command displays the contents of the failure log from /var/log/faillog database file. It also can be used for maintains failure counters and limits. If you run faillog command without arguments, it will display only list of user faillog records who have ever had a login failure.

Synopsis

faillog [options]

Options

The options which apply to the faillog command are:
-a, --all
Display faillog records for all users.
-h, --help
Display help message and exit.
-l, --lock-time SEC
Lock account to SEC seconds after failed login.
-m, --maximum MAX
Set maximum number of login failures after the account is disabled to MAX. Selecting MAX value of 0 has the effect of not placing a limit on the number of failed logins. The maximum failure count should always be 0 for root to prevent a denial of services attack against the system.
-r, --reset
Reset the counters of login failures or one record if used with the -u LOGIN option. Write access to /var/log/faillog is required for this option.
-t, --time DAYS
Display faillog records more recent than DAYS. The -t flag overrides the use of -u.
-u, --user LOGIN
Display faillog record or maintains failure counters and limits (if used with -l, -m or -r options) only for user with LOGIN.

Examples

To display all failed login attempt with following command:

# faillog -a

Sample outputs

Login       Failures Maximum Latest                   On

root            0        0   01/01/70 07:00:00 +0700
bin             0        0   01/01/70 07:00:00 +0700
daemon          0        0   01/01/70 07:00:00 +0700
adm             0        0   01/01/70 07:00:00 +0700
lp              0        0   01/01/70 07:00:00 +0700
sync            0        0   01/01/70 07:00:00 +0700
shutdown        0        0   01/01/70 07:00:00 +0700
halt            0        0   01/01/70 07:00:00 +0700
mail            0        0   01/01/70 07:00:00 +0700
news            0        0   01/01/70 07:00:00 +0700
uucp            0        0   01/01/70 07:00:00 +0700
operator        0        0   01/01/70 07:00:00 +0700

To display failed login attempt for user root with following command:

# faillog -u root

Sample outputs

Login       Failures Maximum Latest                   On

root            0        0   01/01/70 07:00:00 +0700

The post How To Display Failed Login Attempt ? appeared first on lifeLinux: Linux Tips, Hacks, Tutorials, Ebooks.

What is PTY?

A pseudo-terminal (PTY) is a pair of virtual character devices that provide a bidirectional communication channel. One end of the channel is called the master; the other end is called the slave. The slave end of the pseudo-terminal provides an interface that behaves exactly like a classical terminal. A process that expects to be connected to a terminal, can open the slave end of a pseudo-terminal and then be driven by a program that has opened the master end. Anything that is written on the master end is provided to the process on the slave end as though it was input typed on a terminal.

Check maximum number of PTY

Login as root and type the following command

[root@lifelinux ~]# cat /proc/sys/kernel/pty/max

Sample output

4096

Increase the maximum number of PTY temporarily

If you need to increase the PTYs to allow more sessions temporarily. Type the following command

[root@lifelinux ~]# echo 5000 > /proc/sys/kernel/pty/max

The setting is changed instantly but this setting will be erased after the reboot.

Increase the maximum number of PTY permanently

Edit kernel configuration file at /etc/sysctl.conf, enter

[root@lifelinux ~]# vi /etc/sysctl.conf

Add or edit following config directive

kernel.pty.max = 5000

To enable the changes made in sysctl.conf you will need to run the command

[root@lifelinux ~]# sysctl -p

The post How To Increase The Number Of PTY (Pseudo-Terminal Driver) appeared first on lifeLinux: Linux Tips, Hacks, Tutorials, Ebooks.