RHCE7 Study notes 2--get help information

1, Whatis

[[email protected] tmp]# Whatis passwdpasswd (1)-Update user ' s authentication tokenssslpasswd (1SSL)-com Pute Password HASHESPASSWD (5)-Password file

passwd (1)

Refer to the following specific figures to explain:

1 user commands, which can be initiated by anyone. 2 system calls, which are functions provided by the kernel. 3 routines, that is, library functions. 4 device, which is a special file in the/dev directory. 5 file format description, such as/etc/passwd. 6 games, no explanation! 7 Miscellaneous, such as macro command packs, conventions, and so on. 8 system Administrator tool, can only be started by root. 9 Other (Linux-specific) documents used to store kernel routines. N new documents, you may want to move to a more appropriate area. o old documents may be retained for a period of time. L Local documentation, related to this particular system.

For example I want to see password file explanation and help, you can enter: Man 5 passwd, so you can get/etc/passwd file format description, if you do not enter a number, the default is 1;

2. Help

How to use:

[[Email protected] tmp]# passwd --helpusage: passwd [option ...]  <accountname>-k, --keep-tokens       keep non-expired  authentication tokens  -d, --delete             delete the password for the named account  (Root  only)   -l, --lock               lock the password for the named account  (root only)    -u, --unlock            unlock the  password for the named account  (root only)   -e, --expire             expire the password for  the named account&nbSP; (root only)   -f, --force              force operation  -x, --maximum=DAYS       maximum password lifetime  (root only)   -n, --minimum=DAYS       minimum password lifetime  (root only)   -w, --warning=days       number of days warning users receives before  password

3, man

Man XX command/file

Man 5 command/File

Find in Man, press "/keyword", press N to search from top to bottom, press N to look up, press Q to exit;

If you do not know how to find the command specifically how to write, you can use: "man-k keyword" for fuzzy search, you can search out all the commands containing keywords;

Outside content:

Use date to set the system time, the motherboard and BIOS time has not changed, to use the HWCLOCK-W command to synchronize the system and motherboard time;

4, pinfo

Not commonly used, generally use man more

5. Red Hat Support

Not bad for money can be considered;

RHCE7 Study notes 2--get help information