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UNIX for Dummies Questions & Answers
crontab problem
Post 10130 by Kelam_Magnus on Thursday 8th of November 2001 09:34:42 AM
11-08-2001
crontab options
Guest100,
I used to use only "crontab -e" until I found this way of editing the crontab. It is much safer for you and if you make any mistakes it doesn't corrupt your crontab file.
When you look at the options for the manpage for crontab, the first options is "crontab filename".
My only point about saving the crontab out to a file and editing it is 1) so that you will have a copy of it and 2) when you edit this text file that you just saved out, you can execute "crontab filename" to replace the current crontab with the newly edited one. In addition, it prevents you from making a mistake typing while using "crontab -e".
Step 1
Copy out the crontab to a saved file.
$ crontab -l > somefile
Step 2
edit somefile and make changes.
$ vi somefile
Step 3
copy the newly edited file back into place.
$ crontab somefile
This is the safest way to edit the crontab file so that it doesn't get corrupted.
I work for a very large telecom company and this is the company standard for all platforms: SUN, HPUX, and AIX with several different versions on each platform.
In addition, yes you can go to /usr/spool/cron/crontabs and vi the file in question, edit it and save. The file will be recognized by cron because I have done this as well. I have even cut and pasted from a Word document into a telnet session while vi'ing a file in /usr/spool/cron/crontabs file. And there was no corruption of the file when I saved it and ran cron.
Trust me, all of these things work! Can someone else back me up on this? I am not trying to mess you up, only to help you out.
I used to use only "crontab -e" until I found this way of editing the crontab. It is much safer for you and if you make any mistakes it doesn't corrupt your crontab file.
When you look at the options for the manpage for crontab, the first options is "crontab filename".
My only point about saving the crontab out to a file and editing it is 1) so that you will have a copy of it and 2) when you edit this text file that you just saved out, you can execute "crontab filename" to replace the current crontab with the newly edited one. In addition, it prevents you from making a mistake typing while using "crontab -e".
Step 1
Copy out the crontab to a saved file.
$ crontab -l > somefile
Step 2
edit somefile and make changes.
$ vi somefile
Step 3
copy the newly edited file back into place.
$ crontab somefile
This is the safest way to edit the crontab file so that it doesn't get corrupted.
I work for a very large telecom company and this is the company standard for all platforms: SUN, HPUX, and AIX with several different versions on each platform.
In addition, yes you can go to /usr/spool/cron/crontabs and vi the file in question, edit it and save. The file will be recognized by cron because I have done this as well. I have even cut and pasted from a Word document into a telnet session while vi'ing a file in /usr/spool/cron/crontabs file. And there was no corruption of the file when I saved it and ran cron.
Trust me, all of these things work! Can someone else back me up on this? I am not trying to mess you up, only to help you out.
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LEARN ABOUT DEBIAN
passwd
PASSWD(5) File Formats and Conversions PASSWD(5) NAME
passwd - the password file DESCRIPTION
/etc/passwd contains one line for each user account, with seven fields delimited by colons (":"). These fields are: o login name o optional encrypted password o numerical user ID o numerical group ID o user name or comment field o user home directory o optional user command interpreter The encrypted password field may be blank, in which case no password is required to authenticate as the specified login name. However, some applications which read the /etc/passwd file may decide not to permit any access at all if the password field is blank. If the password field is a lower-case "x", then the encrypted password is actually stored in the shadow(5) file instead; there must be a corresponding line in the /etc/shadow file, or else the user account is invalid. If the password field is any other string, then it will be treated as an encrypted password, as specified by crypt(3). The comment field is used by various system utilities, such as finger(1). The home directory field provides the name of the initial working directory. The login program uses this information to set the value of the $HOME environmental variable. The command interpreter field provides the name of the user's command language interpreter, or the name of the initial program to execute. The login program uses this information to set the value of the $SHELL environmental variable. If this field is empty, it defaults to the value /bin/sh. FILES
/etc/passwd User account information. /etc/shadow optional encrypted password file /etc/passwd- Backup file for /etc/passwd. Note that this file is used by the tools of the shadow toolsuite, but not by all user and password management tools. SEE ALSO
crypt(3), getent(1), getpwnam(3), login(1), passwd(1), pwck(8), pwconv(8), pwunconv(8), shadow(5), su(1), sulogin(8). shadow-utils 4.1.5.1 05/25/2012 PASSWD(5)