© 1995-2003 CNET Networks, Inc. All rights reserved. “TechRepublic” and its logo are trademarks of CNET Networks, Inc. Reproduction of this publication in any form is prohibited. This is a single user version and duplication is prohibited. For additional copies please call 1-800-217-4339. at Execute a command or script at a specified time and at regular intervals. at [[-V] [-q queue ] [-f file ] [-m] [-l] [-d] [-b] [-v] time ] | [-c job [ job .]] [-V]: Show the version of at. [-q queue ]: Specifies the queue to use. [-f file ]: Get the job information from a file. [-m]: Email job status to user after completion. [-l]: List the jobs currently in the queue. [-d]: Remove the job from the queue. [-b]: Allows a job to be run based on the current system status. [-v]: Shows completed jobs still in the queue. time : The time that the job should run. MM/DD/YY and/or HH:MM specification is supported. [-c job [ job .]]: The task that should be performed at the time specified. date Display and set the system date and time Date [-u | --utc | --universal] [-d | --date= datestring ] [-R | --rfc-822] [[ yyyy ] mmddhhmm [ yy ][. ss ]] [-u | --utc | --universal]: Print/set universal time. [-d | --date= datestring ]: Display the time shown by the string specified here. [-R | --rfc-822]: Show the time in rfc-822 format. [[ yyyy ] mmddhhmm [ yy ][ .ss ]]: The format for the date and time. halt Power down or restart the system. halt [-d] [-f] [-h] [-i] [-n] [-p] [-w] [-d]: Don’t write wtmp record before shutting down. [-f]: Force a shutdown or restart. [-h]: Place hard drives into standby before shutting down. [-i]: Shut down network interfaces before shutting down. [-n]: Don’t sync before shutting down. Implies a -d. [-p]: Halt with a poweroff rather than restart. [-w]: Don’t shutdown or restart, but write wtmp record. kill Terminate a system process. kill [-l [ signal ] | [-s signal | -p]] [-a] [--] pid . [-l signal]: Print a list of signal names. Red Hat Linux 9 has 63 signal names. [-s signal]: The signal to send to the process. Signal 9 for example, will send a SIGKILL signal to a process effectively killing it. [-p]: Just print the process id for the specified process and do not send it any signals. [-a]: Don’t restrict commandname-to-pid conversion. newaliases Rebuild the mail aliases database. Newaliases does not take any parameters and is functionally equivalent to sendmail -bi. passwd Manage user’s passwords. passwd [-d | --delete] [-f | --force] [-i | --inactive=days] [-k | --keep-tokens] [-l | --lock] [-n | --minimum= days ] [-S | --status] [--stdin] [-u | --unlock] [-w | --warning= days ] [-x | --maximum= days ] [username] [-d | --delete]: Root only: Delete the password for the user. [-f | --force]: Force the operation to complete. [-i | --inactive= days ]: Root only: The account grace period. The number of days after a password expires before an account is disabled. [-k | --keep-tokens]: Keep authentication tokens that have not expired. [-l | --lock]: Root only: Lock the specified account. [-n | --minimum= days ]: Root only: The minimum number of days that must pass before the password can be changed again. [-S | --status]: Root only: Display the password status of the specified account. [-u | --unlock]: Root only: Unlock the specified account. [-w | --warning= days ]: Root only: The number of days warning that a user receives that his password is to expire. [-x | --maximum= days ]: Root only: The maximum life of a password. [username]: The username on which to perform the operation. ps Display process statistics. ps [a] [-A] [-a] [C] [c] [-C processname ] [{--cols num | --columns num | --width num}] [-d] [e] [-e] [{f | --forest}] [-f] [g] [{-G RGID | --Group RGID }] [{-g groupname | --group groupname }] [{h | --no-headers}] [-H] [--headers] [--html] [{j | -j}] [{l | -l}] [L] [{--lines num | --rows num}] [{m | -m}] [n] [{N | -n}] [-N | --deselect] [{--nul | --null | --zero}] [O] [{o | -o | --format}] [{p pid | -p pid | --pid pid}] [r] [s] [{S | --cumulative}] [{-s session | --sid session}] [--sort sortkey] [{-t tty | t tty | T tty | --tty tty}] [{-U RUID | --User RUID }] [{-u userid | --user userid }] [v] [{w | -w}] [x] [X] [-y] [a]: Show information for all processes on this terminal including those belonging to other users [-A]: Show information for all processes [-a]: Show information for all processes with a TTY except session leaders [C]: Show the raw CPU time [c]: Show the true command name [-C processname ]: Show information for processes that match the name specified [{--cols num | --columns num | --width num}]: The screen width [-d]: Show information for all processes except session leaders [e]: Show the environment after each command [-e]: Show information for all processes with a TTY except session leaders [{f | --forest}]: Display: process listing with ASCII art [-f]: Display: full process listing [g]: Really, we mean it this time. Show ALL process information. [{-G RGID | --Group RGID }]: Show information for processes with a matching real group ID [{-g groupname | --group groupname}]: Show information for processes matching the effective group name [{h | --no-headers}]: Display: do not print header lines [-H]: Display: process hierachy [--headers]: Repeat the header lines [--html]: Print html escaped output [{j | -j}]: Display: jobs format [{l | -l}]: Display: long listing format [L]: List all formats [{--lines num | --rows num }]: Set the screen height [{m | -m}]: Display: all threads [n]: Display: numeric output for WCHAN and USER [{N | -n}]: Set namelist file [-N | --deselect]: Negate the selection [{--nul | --null | --zero}]: Unjustified output with NULs [O]: Sort order: overloaded [{o | -o | --format}]: Display: User define format [{p pid | -p pid | --pid pid}]: Show information for processes with a matching process ID [r]: Show information for running processes [s]: Display: Signal format [{S | --cumulative}]: Include dead child process information [{-s session | --sid session }]: Show information for processes belonging to the matching session [--sort sortkey]: Sort order [{-t tty | t tty | T tty | --tty tty}]: Show information for processes on the terminal specified [{-U RUID | --User RUID }]: Show information for processes with a matching real user ID [{-u userid | --user userid }]: Show information for processes with a matching effective user ID [v]: Display: virtual memory format [{w | -w}]: Display: wide output [x]: Show information for processes that do not have controlling TTYs [X]: Display: Linux i386 format [-y]: Don’t show flags shutdown Shut down the system. Must be logged in as root. shutdown [-a] [-c] [-f] [-F] [-h] [-n] [-k] [-r] [-t seconds ] time [ message ] [-a]: Use /etc/shutdown.allow. [-c]: Cancel an in-progress shutdown. [-f]: Skip the file system check upon reboot. [-F]: Force a file system check upon reboot. [-h]: Halt the system after the shutdown is complete. [-n]: Go down fast and don’t use ‘init’. [-k]: Only warn about a pending shutdown but don’t actually do it. [-r]: Reboot the system after the shutdown. [-t seconds ]: The number of seconds to wait before sending the kill signal. time : The time to shutdown (ie - ‘now’) [ message ]: The warning message to send to attached users. sudo Run a command as another user. sudo [-k] | [-K] | [-l] | [-v] | [-V] | [-b] [-H] [-P] [-S] [-p prompt ] [-u username | # uid ] [-s] | [ command ] [-k]: “kill”: invalidates a user’s timestamp. [-K]: “sure kill”: remove a user’s timestamp. [-l]: Shows the allowed commands for the user. [-v]: Validate the user’s timestamp. [-V]: Version [-b]: Runs the specified command in the background. [-H]: Sets the HOME variable to match the user specified. [-P]: Preserve the user’s group vector. [-S]: Causes sudo to read password from file rather than terminal. [-p prompt ]: Use a custom password prompt. [-u username | # uid ]: The user or user ID. [-s]: Runs the shell specified in the SHELL variable. [ command ]: The command to run. top top [b] [c] [C] [d delay ] [i] [p pid ] [q] [s] [S] [n iterations ] [b]: Batch mode. Use with n to specify the number of iterations. [c]: Display command line rather than command name. [C]: SMP systems: display total CPU statistics. [d delay ]: The delay between screen updates. [i]: Ignore idle and zombie processes. [p pid ]: Monitor processes with the specified process ID. This parameter can be specified 20 times. [q]: Refreshes without delay. [s]: Run in secure mode. [S]: Show process utilization as a cumulative figure building on the previous process. [n iterations ]: Use with b to run a certain number of times. useradd Add a new user to the system. Must be logged in as root. useradd [-A { method | DEFAULT}, .] [-c comment ] [-d homedir ] [-e expiredate] [-f inactivetime ] [-g initialgroup ] [-G group [ .]] [-m [-k skeletondir ]] [-n] [-r] [-s shell ] [-u uid [-o]] login [-A { method | DEFAULT}, .]: The name of the program that will authenticate the user. [-c comment ]: A comment to associate with the user account. [-d homedir ]: The location of the user’s home directory. SYSTEM Continued on next page